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Cap. 13.19 electricity 25/08/15 No. 4/2002

ELECTRICITY ACT [chapter 13:19]
ARRANGEMENT OF SECTIONS

PART 1
PRELIMINARY

Section
1. Short title and date of commencement.
2. Interpretation

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 PART II
Establishment, Functions and powers of Commission
3. Establishment of Commission
4. Objects and functions of Commission

PART III
Electricity Regulatory
5. Commissioners
6. Terms of office and conditions of service of Commissioners
7. Disqualifications for appointment as Commissioner
8. Vacation of office by Commissioner
9. Dismissal or suspension of Commissioners
10. Filling of vacancies on Commission
11. Chairman and vice-chairman of Commission
12. Meetings and Procedures of Commission
13. Remuneration and expenses of Commissioners.
14. Commissioners to disclose certain connections and interests
15. Validity of decisions and acts of Commission
16. Proceedings of Commission
17. Decisions and orders of Commission to be in writing
18. Commission to give notice to interested parties
19. Commission to consult experts on technical questions

PART IV
Hearings By Commission
20. Hearings by Commission.
21. Questions of law may be referred to High Court
22. Powers of Commission to summon witnesses and to take
evidence at hearings
23. Penalty for witness failing to attend hearing or give evidence or
produce documents
24. Penalty for giving false evidence at hearing.

PART V
Financial Provisions
25. Annuals programs and budgets of Commission
26. Funds of Commission
27. Surplus funds of Commission to be appropriated to Rural
Electrification Fund
28. Financial year f Commission
29. Accounts of Commission
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30. Audit of Commission’s Accounts
31. Powers of Auditors

PART VI
Levies
32. Imposition of levies
33. Withdrawal, suspension or increase of levies
34. Recovery of unpaid levies

PART VII
Miscellaneous Provisions Relating to Commission
35. Minister may give policy directions
36. Execution of Contracts and instruments by Commission
37. Reports of Commission
38. Staff of Commission
39. Exemption from liability for Commission

PART VIII
Licenses
40. Licensing Requirements
41. General duties of licenses
42. Generation Licenses
43. Transmission and bulk supply licenses
44. Distribution and retail supply licenses.
45. Restriction on licenses
46. License Application
47. Terms and Conditions of licenses
48. Renewal of licenses
49. Amendment of licenses
50. Enforcement of licenses
51. Cancellation of licenses
52. Pricing methodology and accounting procedures
53. Electricity tariffs and prices
54. Special provisions relating to transmission and distribution
licenses
55. Use of certain conduits for electricity purposes
56. Notice of construction of railway and telecommunication works
and control of other works

PART IX

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 Consumer Protection and Licensee Performance
Standards
57. Consumer Protection Standards
58. Performance standards and codes

PART X
Competition and Market Power
59. Regulated Services: competition and market power.

PART XI
Offences
60. False statements and declarations
61. Other offences

PART XII
General
62. Inspections
63. Dispute resolution
64. Appeals
65. Regulations
66. Disclosure of confidential information and use of information
acquired by inspectors etc for personal gain

PART XIII
Transitional Provisions, Repeals and Savings
67. Interpretation in PART XIII
68. Formation of successor companies.
69. Initial shareholding in successor companies
70. Transfer of assets and liabilities of Authority to successor
companies
71. Issue of securities in consideration for transfer assets
72. Conversion of loans transferred to successor companies.
73. Transfer of employees to successor companies and conditions of
service of transferred employees.
74. Minister may give directions to Authority
75. Successor companies deemed to be licensed
76. Repeal of Cap 13:05
77. Savings and transitional provisions

FIRST SCHEDULE: Ancillary powers of Commission

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 SECOND SCHEDULE: Rights, powers and duties of
transmission or distribution licenses.

ZIMBABWE
ACT

To provide for the establishment of the Zimbabwe Electricity Regulatory Commission; to

provide for its functions and management; to provide for the licensing and regulation of the
generation, transmission, distribution and supply of electricity; to provide for the repeal of the
Electricity Act [Chapter 13:05]; and to provide for matters incidental to or connected with the
foregoing.

ENACTED by the President and the Parliament of Zimbabwe

PART 1
PRELIMINARY

1. Short Title and Date of Commencement

(i) This Act may be cited as the Electricity Act [Chapter 13:19]
(ii) This Act shall come into operation on a date to be fixed by the President by
statutory instruments:

2. INTERPRETATION
(I) In this Act –
(iii) “affiliate”, in relation to license, means any holding company or subsidiary of
the licensee or any subsidiary of a holding company of the licensee, within the
meaning of subsidiary as defined in section 143 of the Companies Act [Chapter
24:03] and includes (unless the Commission decides to the contrary) an entity in
which the licensee owns or controls, directly or indirectly, ten per centum or
more of the voting securities of such entity;
“ancillary services” means those functions necessary for the reliable operation of a
power system, which may include, but are not limited to, services that would provide or
permit the following-

a) Facilities scheduling, control and dispatch

b) Reactive power and voltage control
c) Frequency regulation
d) Operating power reserves;
“Authority” means the Zimbabwe Electricity Supply Authority established in terms of
the electricity Act [Chapter 13:05];
“bulk supply license” means a license to supply electricity to one or more licenses for
resale referred to in subsection (4) of section forty-three;
“code of conduct” means any rules established by the Commission governing behavior,
relationships and practices between licensees and their affiliates and between
licensees themselves;
“Commission” means the Electricity Regulatory Commission established in terms of
section three;

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“Consumer” means any end-user of electricity who is a customer of a licensee and
includes, for purposes of filing a complaint with the Commission, or for any other
reason that the Commission may determine, a person who is temporarily
disconnected or who has applied for, but has yet to receive, an electricity service or
is otherwise without electricity service;
“Competition and Tariff Commission” means Competition and Tariff Commission
established in terms of the Competition Act, 1996 (No. 7 of 1996);
“Customer”, in relation to a licensee, means a consumer of any service provided by
such licensee under a contractual or other arrangement with such consumer;
“control area” means a transmission system, or interconnected transmission systems
and interconnected generating units, bounded by metering and telemetry
equipment that permits a system operator to apply a generation scheme in order to-
a) Match the electrical output of the generating stations within the control area and
energy purchased from entities outside the control area, with the load within the
control area.
b) Maintain scheduled interchange with other areas, within the limits of good
utility practice;
c) Maintain the frequency of the control area’s electric power systems within
reasonable limits in accordance with good utility practice;
d) Maintain power flow on transmission facilities within appropriate limits to
preserve reliability;
e) Provide sufficient generating capacity to maintain operating reserves in
accordance with good utility practice;
“deemed licensee” means a person deemed in terms of section seventy-five to be
licensed in terms of this Act:
“distribution”, in relation to electricity means the delivery of electricity to consumers;
“distribution system” means the facilities consisting wholly or mainly of electric lines
used for the distribution of electricity from grid supply points to the point of
delivery to consumers, and includes any electrical plant and meters operated in
connection with the distribution of electricity, but does not include in any part of a
transmission system;
“electric power system” means any system that enables the generation, transmission,
distribution and supply of electricity;
“electric industry” means the persons who in Zimbabwe are engaged in the business of
providing electricity services or operating electric power systems;
“electricity undertaking” means any undertaking which engages in the business of
generating, transmitting, distributing or supplying electricity;
“generating station” means a station for generating electricity, including buildings,
plant and machinery and all accessories used for that purpose and the site to be for
the station and accessories.
“generation” means the production at a generating station of electric power, energy and
other generation products such as, but not limited to, reactive power.
“generation license” means a license referred to in section forty-two;
“grid code” means instructions, rules procedures or guidelines for the operation and
planning of an interconnected power system and accounting requirements relating
thereto;
“independent transmission facility” means any transmission facility referred to in
subsection (3) of section forty-three, that is built, owned and maintained by an
independent transmission licensee, and which may include but not be limited to a
transmission facility between two transmission grids; between two points on a

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 single transmission grid; between a generating station and a transmission grid; or
between a distribution system and a transmission grid;
“independent transmission license” means a transmission license in terms of subsection
(3) of section forty-three to a company that is not an affiliate of a primary
transmission licensee;
“license” means a generation, transmission, bulk supply, distribution or retail supply
license issued by the Commission in terms of section forty-six
“licensee” means any person who holds a license issued in terms of this Act;
“lifeline tariff” means a tariff set by the Commission with prices that incorporate cross
subsidies by other customer which may be enjoyed by such a group of consumers
as the Commission may designate;
“local authority” means a municipal council, town council, rural district council, local
board or provincial authority;
“market power” means the ability of a seller or group of sellers to profitably maintain
prices above, competitive levels, or to maintain prices while reducing the quality
of product or service provided, for a significant period of time;
“Minister” means the Minister of Mines and Energy, or any other Minister to whom the
President may from time to time assign the administration of this Act;
“owner” in relation to land or premises means-
a) The person registered n the Deeds Registry as the owner of land or premises; or
b) In the case of the land vested in the President, other than-
(i) Communal Land
(ii) Forest land; or
(iii) Land referred to in paragraph €;
The Minister responsible for the management or administration o land; or
c) In the case of Communal Land, the Minister responsible for the Administration of
Communal Land Act [Chapter 20:04]; or
d) In the case of forest land, the Forestry Commission; or
e) Any person who lawfully holds or occupies land, including State land, in
accordance with an agreement or an enactment under which he is entitled to obtain
title to the land on the fulfilment of conditions prescribed in the agreement or
enactment;
And includes-
(i) The legal representative of an owner referred to in paragraph (a) or (e) and
(ii) The liquidator of a company which is an owner referred to in paragraph (a) or
(e) and which is in liquidation;
(iii) “prices” means the prices, rates, tolls and charges that apply to a service
provided by a licensee;
“primary transmission license” means a transmission license issued in terms of
subsection (1) or (2) of section forty-three
“retail supply license” means a license to supply electricity to one or more customers
referred to in subsection (3) of section forty-four
“Rural Electrification Fund” and “Rural Electrification Fund Board” means the Fund
and Board established in terms of the Rural Electrification Act [Chapter 13:20] (Act no.
3 of 2002);
“street” means any street, highway, or road, or any part of a street, highway or road,
whether or not at any time it has been declared to be a road in terms of the Roads Act
[Chapter 13:18], and includes-
a) any bride, ferry or pontoon over which such street, highway or road passes; and
b) any drift in the line of such street, highway or road; and

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c) any approach, culvert, cutting, dam, ditch, drain, embankment, fence, grid, guard,
kerb, parapet, subway or other work or thing belonging to or connected with or
forming part of such street, highway or road; and
d) any sanitary land and private street;
“supply” means the sale or trading of electricity, and “supplier” shall be construed
accordingly;
“tariff” means a tariff approved by the Commission in terms of section fifty-three that
specifies the prices and terms and conditions under which any electricity service I to be
provided.
“trading” means any form of marketing, brokering or intermediation in the sale or
purchase of electricity, whether or not such trading entails the purchase of electricity
for resale and whether or not title is taken to the electricity sold or transferred;
“transmission” means the conveyance of electric power and energy over a transmission
system;
“transmission license” means a primary o independent transmission license;
“transmission system” means a system consisting wholly or mainly of high voltage
electric lines for the conveyance of electricity within an electricity undertaking or from
one electricity undertaking to another, including any transmission lines, transformers,
switchgear, and other works necessary for and used in connection with such electrical
equipment, and such buildings as may be required to accommodate the transformers,
switchgear and other works;
“Zambezi River Authority” means the Authority referred to in the Zambezi River
Authority Act [Chapter 20:23]

PART II
Establishment, Functions and Powers of Commission

3 Establishment of Commission
There is hereby established Commission, to be known as the electricity Regulatory
Commission, which shall be a body corporate capable of suing, and being sued in
its corporate name and, subject to this Act, of perform all acts that bodies corporate
may by law perform.

4 Objects and Functions of Commission

(1) Subject to this Act, the Commission shall have the following principal objects-
a) to create, promote and preserve efficient industry and market structures for the
provision f electricity services, and to ensure the optimal utilization of
resources for the provision of such services
b) to maximize access to electricity services by promoting and facilitating
consumer connections to distribution systems in both rural and urban areas;
c) to ensure that an adequate supply of electricity is available to consumers

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 d) to ensure that the prices charged by licensees are fair in the light of the need
for prices to be sufficient to allow licensees to finance their activities and
obtain reasonable earnings for their efficient operation;
e) to ensure that safety, security and quality of service in the production and
delivery of electricity to consumers;
f) to ensure that regulation is fair and balanced for licensees, consumers,
investors and other stakeholders in the electricity industry

(2) For the furtherance of the objects referred in subsection *(1), the Commission
shall perform the following functions-
a) promote and implement competition and private sector participation, when
and where feasible;
b) establish or approve appropriate operating codes, grid codes and safety,
security, reliability and quality standards;
c) establish appropriate consumer rights and obligations regarding the provision
and use of electricity services;
d) license and regulate persons engaged in the generation, transmission,
distribution and supply of electricity;
e) aid and advise stakeholders in the electricity sector in matters related to the
generation, transmission, distribution and supply of electricity;
f) advise consumers regarding the efficient use of electricity;
g) advise the Minister on matters related to electricity systems and services;
h) participate internationally in matters related to electricity services;
i) arbitrate and mediate disputes among licensees and between licensees and
consumers;
j) issue guidelines on such matters within its sphere of competence as it
determines will be in public interest;
k) undertake such other thing which it considers is necessary o convenient for the
better carrying out of or giving effect to the objects of the Commission.

(3) Subject to this Act, the commission shall have power to do or cause to be done,
either by itself or through its agents, all or any of the thinks specified in the First Schedule,
either absolutely or conditionally and either solely or jointly with others.

(4) In the discharge of its functions, the Commission shall consult from time to time, to
the extent the Commission considers appropriate, such persons or groups of persons, who are
or are likely to be affected by the decisions or orders of the Commission including licenses, the
Rural Electrification Fund Board, the Zambezi River Authority, consumers of electricity,
potential investors in electricity services and other interested parties.

(5) Subject to this Act, the Commission shall not, in the lawful exercise of its functions
under this Act, be subject to the direction or control of any person or Authority.

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 PART III

ELECTRICITY REGULATORY COMMISSION

5 Commissioners

(1) subject to subsection (2), the commission shall consist of not less than five and not
more than seven Commissioners, appointed in terms of this Act by the President
after consultation with the Minister.

(2) The President shall appoint Commissioners from a list of names submitted to him
by the Minister.

Provided that the Minister shall submit not more than two names for each position
or vacant in the Commission to be filled.

(3) In appointing Commissioners, the President shall endeavor to secure that they are
chosen from the public and private sectors and in particular that at least two
members are chosen for their experience or professional qualifications in the
following fields or areas of competence-
(a) The generation, transmission or distribution of electricity;
(b) Law, accountancy, economics, finance or administration.

6. Terms of office and conditions of services

(1) Subject to this Part, a Commissioner shall hold office for a period of three years.

(2) A Commissioner shall continue in office after the expiry of his term until he has
been re-appointed or his successor has been appointed.

Provided that a Commissioner shall not hold office in terms of this subsection for
longer than six months.

(3) Subject to section fourteen, a Commissioner shall hold office on such terms and
conditions as the President may fix in relation to Commissioners generally.

(4) A Commissioner whole term of office has expired is eligible for re-appointment:

Provided that no Commissioner may be re-appointed for a third term in office.

(5) The terms and conditions of office of a Commissioner shall not, without the
Commissioner’s consent, be altered to his detriment during his tenure of office.

7 Disqualifications for appointment as Commissioner

(1) A person shall not be appointed as a Commissioner and no person shall be qualified
to hold office as a Commissioner who-
(a) is neither a citizen of Zimbabwe nor permanently resident in Zimbabwe or;

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 (b) has a financial interest in any business connected with the generation,
transmission, distribution and supply of electricity, or is engaged in any activity
connected with any electricity serve or electric power system, or is married or
connected to or associated with a person who has such an interest or is engaged
in such an activity, unless the President is satisfied that the interest or activity is
indirect and passive and will not interfere with the person’s impartial discharge
of his duties as a Commissioner; or

(c) Has, in terms of a law in force in any country-

(i) been adjudged or otherwise declared insolvent or bankrupt and has not
been rehabilitated or discharged; or
(ii) made an assignment to, or arrangement or composition with, his
creditors which has not been rescinded or set aside; or

(d) Has, within the period of five years immediately preceding the date of his
proposed appointment, been convicted-
(i) in Zimbabwe, of an offence; or
(ii) outside Zimbabwe, in respect of conduct which, if committed in
Zimbabwe, would constitute an offence; and
(iii) sentenced to a term of imprisonment imposed without the option of a
fine, whether or not any portion has been suspended and has not
received a free pardon.

(2) A person who is-

(a) a member of Parliament or
(b) a member of two or more other statutory bodies:
shall not be appointed as a Commissioner nor shall he be qualified to hold office as a
Commissioner.

(3) For the purposes of paragraph (b) of subsection (2) a person who is appointed to a
council, board or other authority which is a statutory body or which is responsible
for the administration of the affairs of a statutory body shall be regarded as a
member of that statutory body.

8 Vacation of office by Commissioner

A commissioner shall vacate his office and his office shall become vacant-
(a) three months after the date upon which he gives notice in writing to the Minister of
his intention to resign, or on the expiry of such other period of notice as he and the
Minister may agree; or
(b) on the date be begins to serve a sentence of imprisonment imposed without the
option of a fine-
(i) in Zimbabwe in respect of an offence; or
(ii) outside Zimbabwe, in respect of conduct which, if committed in Zimbabwe,
would constitute an offence; or
(iii) if he becomes disqualified in terms of paragraph (a), (b) or (c) of sub-section
(1) of section seven or in terms of subsection (2) of that section, to hold
office as a Commissioner; or
(iv) if he is required in terms of section nine to vacate his office.

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9 Dismissal or suspension of Commissioners

(1) The President may require a Commissioner to vacate his office if the
Commissioner-
(a) has, subject to subsection (3), been found to have conducted himself in a
manner that renders him unsuitable as a Commissioner, including a
contravention of section fourteen or subsection (2) of section thirty-one; or
(b) has failed to comply with any term or condition of his office fixed by the
President in terms of subsection (3) of section six; or
(c) is mentally or physically incapable of efficiently carrying out his functions as a
Commissioner.

(2) The President, on the recommendation of the Minister, may suspend a

Commissioner-
(a) whom he suspects on reasonable grounds of having been guilty of conduct
referred to in paragraph (a) of subsection (1); or
(b) against whom criminal proceedings have been instituted for an offence in
respect of which a sentence of imprisonment without the option of a fine may be
imposed;
and while that Commissioner suspended he shall not carry out any functions as a
Commissioner.

(3) A Commissioner suspended in terms of paragraph (a) of subsection (2) shall be

given notice in writing at the time of the suspension of the grounds for the
suspension and the Minister shall, within fourteen days of such notice, set up la
board of inquiry of not more than three persons chaired by a person who has held or
holds office as a judge to inquire into the question of the removal of the
Commissioner.

(4) A board appointed under subsection (3) shall have the same rights and powers as
commissioners under the Commissions of Inquiry Act [Chapter 10:07].

(5) After due inquiry a board appointed under subsection (3) must report its findings in
writing to the President together with its recommendation as to whether or not the
commissioner must be removed from the office.

(6) A Commissioner removed in terms of this section shall not be eligible for
reappointment nor may he serve the Commission in any other capacity.

10 Filling of vacancies on Commission

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 Subject to section five on the death of or vacation of office by a Commissioner the
President shall appoint a qualified person to fill the vacancy.

11 Chairman and Vice-Chairman of Commission

(1) The President shall designate one of the Commissioners as chairman of the
Commission and another Commissioner as vice-chairman of the Commission.
(2) the vice-chairman of the Commission shall perform the chairman’s functions
whenever the chairman is for any reason unable to perform them.
(3) The chairman or vice-chairman of the Commission may at any time resign his office
as such upon one month’s notice in writing to the Minister.
(4) Whenever the office of chairman or vice-chairman of the commission falls vacant,
the President shall select anther Commissioner to fill the vacancy within three
weeks.

12 Meetings and Procedure of Commission

(1) The Commission shall meet for the dispatch of business as often as is necessary or
expedient and, subject to this section, may adjourn, close and otherwise regulate its
meetings and procedure as it thinks fit.
(2) The chairman or in his absence, the vice-chairman of the Commission shall preside
at all meetings of the commission.
(3) subject to section fourteen, at all meetings of the commission each Commissioner
present shall have one vote on each question before the Commission and in the event of
an equality of votes, the chairman of the Commission shall have a casting vote in
addition to a deliberative vote.
(4) The Commission may conduct its business through circulars to all the
Commissioners, this subsection shall not apply to such matter.

13 Remuneration and expenses of Commissioners

(1) Commissioners shall be paid from the funds of the Commission –
(a) such remuneration, if any, as the Minister may from time to time fix for such
Commissioners; and
(b) such allowances, if any, as the Minister may from time to time fix to meet any
reasonable expenses incurred by such Commissioners in connection with the
business of the Commission.

(2) The remuneration of a Commissioner shall not, without the commissioner’s consent,
be altered to his detriment during his tenure of office.

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14 Commissioners to disclose certain connections and interests
(1) in this section –
“relative”, in relation to a Commissioner, means the Commissioner’s spouse, child,
parent, brother or sister.
(2) If –
(a) a Commissioner –
(i) knowingly acquires or holds a direct or indirect pecuniary interest in any matter
that is under consideration by the Commission; or
(ii) owns any property or has a right in property or a direct or indirect pecuniary
interest in a company or association of persons which results in the
Commissioner’s private interests coming or appearing to come into conflict
with his functions as a Commissioner; or
(iii) Knows or has reason to believe that a relative of his –
(A) Has acquired or holds a direct or indirect pecuniary interest in any
matter that is under consideration by the Commission; or
(B) Owns any property or has a right in any property or a direct or
indirect pecuniary interest in a company or association of persons
which results in the Commissioner’s private interests coming or
appearing to come into conflict with his functions as a
Commissioner; or
(b) For any reason the private interests or a commissioner come into conflict with his
functions as a Commissioner;
The Commissioner shall forthwith disclose the fact to the Commission.

(3) A Commissioner referred to in subsection (2) shall take no part in the consideration
or discussion of, or vote on, any question before the Commission which relates to
any contract, right, immovable property or interest referred to in that subsection.

(4) A Commissioner who contravenes subsection (2) or (3) shall be guilty of an offence
and liable to a fine not exceeding two thousand dollars or to imprisonment for a
period not exceeding three months or to both such fine and such imprisonment.

15 Validity of decisions and acts of Commission

(1) No decision or act of the Commission or act done under the direction of the
Commission shall be invalid on the ground that –
(a) the commission consisted of fewer than the minimum number of persons
prescribed in subsection (1) of section five; or
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 (b) a disqualified person acted as a Commissioner at the time the decision was
taken or act was done or authorized.

(2) If a Commissioner referred to in section fourteen takes part in the consideration

of a matter in which his private interests are in conflict with his functions as
Commissioner or if a decision or act would, but for subsection (1), be any such
decision or action as soon as possible after they become aware that the decision
or action was taken in the circumstances described in section fourteen or
subsection (1).

16 Proceedings of Commission
(1) The commission shall be entitled to conduct its proceedings, consultations and
hearings at its headquarters or at any other place in Zimbabwe.
(2) The manner in which the Commission shall discharge its functions and conduct
its proceedings, consultations and hearings, including procedures for the
participation of licenses, customers and other persons, shall be as prescribed in
regulations made in terms of section sixty-five.

17 Decisions and orders of Commission to be in writing

(1) The chairman of the Commission shall ensure that every decision and order by
the Commission –
(a) contains the reasons for the decision or order;
(b) is properly recorded in writing;
(c) is made available to all parties interested in the decision or order and may be
obtained or inspected by members of the public at reasonable times and places.

(2) Every recommendation, declaration, decision or order of the Commission, if

purporting to be signed by a person describing himself as the chairman of the
Commission, shall, unless the contrary is shown, be deemed to be made by the
Commission and to have been so signed and may be proved by the production
of a certified copy thereof.

18 Commission to give notice to interested parties

Where the Commission is required or otherwise decides to hold a hearing, all persons
having an interest in such matter shall, as far as reasonably practicable, be notified of
the questions at issue and given facilities for making representations.

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19 Commission to consult experts on technical questions
When any matter arises which entails the consideration of any professional or technical
question, the Commission may consult such persons as may be qualified to advise
thereon.

PART IV
HEARING BY COMMISSION

20 Hearings by Commission
The Commission may hold a hearing into any matter, which under this Act or any other
enactment it is required or permitted to consider, or which it is required or permitted to
take any action.

21 Questions of law may be referred to High Court

(1) If any question of law arises in the course of a hearing under this Part, the
Commission may, om its own initiative or at the request of any interested party
to the hearing, reserve that question for the decision of the High Court.
(2) Where a question has been reserved in terms of subsection (1), the Commission
shall state the question in the form of a special case and file it with the Registrar
of the High Court.
(3) The procedure to be followed on a special case stated in terms of subsection (2)
and the powers of the High Court in regard to it, shall be as set out in the High
Court Act [Chapter 7:06] and rules made under that Act in regard to special
cases.

22 Powers of Commission to summon witnesses and to take evidence at hearings

(1) For the purpose of any hearing, the Commission shall have the same powers as
a magistrate’s court to summon witnesses, to cause the oath to be administered
to them, to examine them and to call for the production of documents.
(2) A subpoena for the attendance of a witness or for the production of any book,
document or record before the Commission shall be signed and issued by the
chairman of the Commission, and shall be served in the same manner as a
subpoena for the attendance of a witness at a criminal trial in a magistrates’
court.
(3) Any person subpoenaed to give evidence or to produce any book, document or
record or giving evidence before the Commission shall be entitled to the same
privileges and immunities as if he were subpoenaed to attend or were giving
evidence at a trial in a magistrates’ court.
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23 Penalty for witnesses failing to attend hearing or give evidence or produce
documents
Any person who has been subpoenaed to give evidence or to produce any book,
document or record at a hearing of the Commission and who –
(a) Fails, without reasonable excuse, to attend in obedience to the subpoena; or
(b) At the hearing –
(i) Refuses, without reasonable excuse, to be sworn as a witness; or
(ii) Having been sworn, refuses, without reasonable excuse, to answer fully and
satisfactory any question lawfully put to him, not being a question he may
refuse to answer in terms of subsection (3) of section twenty-two; or
(iii) Refuses to, without reasonable excuse, to produce any such book, document
or record he is lawfully required to produce;
Shall be guilty of an offence and liable to a fine not exceeding two thousand five
hundred dollars or to imprisonment for a period not exceeding three months or to
both such fine and such imprisonment.

24 Penalty of giving false evidence at hearing

Any person who, after having been duly sworn, willfully gives false evidence before
the Commission, known such evidence to be false or not knowing or believing it to be
true, may be charged with perjury.

PART V
FINANCIAL PROVISIONS

25 Annual Programmes and Budgets of Commission

(1) On or before the beginning of every financial year the Commission shall
prepare and submit to the Minister a budget showing the expenditure which the
Commission proposes to incur in respect of that financial year.

(2) During any financial year the Commission may prepare and submit to the
Minister a supplementary budget relating to expenditure which –
(a) was not, for good reason, provided for in the annual budget; or
(b) was inadequately provided for in the annual budget due to unforeseen
circumstances.
(3) A supplementary budget shall be deemed to form part of the annual budget of
the Commission for the financial year to which it relates.

17
 (4) The Commission may vary a budget prepared under this section:
Provided that no variation be made to which has the effect of increasing the total
amount of expenditure provided for in the budget.

26 Funds of Commission
The funds of Commission shall consist of –
(a) Feed, charged and other income accruing to the Commission from the issuing of
licenses and the doing of other thinks done by it in terms of this Act, and
(b) Levies, together with any interest or surcharge payable thereon, collected in terms
of Part VI; and
(c) Such other moneys as may vest in or accrue to the Commission, whether in the
course of its operations or otherwise.

27 Surplus funds of Commission to be appropriated to Rural Electrification Fund

Any surplus of income over expenditure at the end of the Commission’s financial year
shall be appropriated to the Rural Electrification Fund.

28 Financial year of Commission

The financial year of the Commission shall be the period of twelve months ending on
the 31st of December in each year or such other period as the Minister may, by notice in
a statutory instrument determine.

29 Accounts of Commission
(1) The commission shall ensure that proper accounts and other records relating to
such accounts are kept in respect of all the Commission’s activities, funds and
property including such particular accounts and records as the Minister may
require.
(2) Not later than three months after the end of each financial year of the
Commission, the Commission shall prepare and submit to the Minister a
statement of accounts in respect of that financial year.

30 Audit of Commission’s accounts

(1) Subject to the Audit and Exchequer Act [Chapter 22:03], the Commission shall
appoint as auditors on or more persons approved by the Minister who are
registered as public auditors in terms of the Public Accountants and Auditors
Act [Chapter 27:12].

18
 (2) The accounts kept by the Commission in terms of subsection (1) of section
twenty-nine shall be examined by the auditors appointed in terms of subsection
(1).
(3) The auditors appointed in terms of subsection (1) shall make a report to the
Commission and the Minister on the statement of accounts prepared in terms of
subsection (2) of section twenty-nine and such report shall state whether or not
in their opinion the statement of accounts gives a true and fair view of the
Commission’s affairs.
(4) The Minister may require the Commission to obtain from its auditors appointed
in terms of subsection (1) such other reports, statements or explanations in
connection with the Commission’s operations, funds and property as the
Minister may consider necessary and the Commission shall forthwith comply
with any such requirement.

31 Powers of auditors
(1) an auditor referred to in section thirty shall be entitled at all reasonable times to
require to be produced to him all accounts and other record relating to such
accounts which are kept by the Commission or its agents and to require from
any Commissioner or employee or agent of the Commission such information
and explanations as in the auditor’s opinion are necessary for the purposes of his
audit.
(2) Any Commissioner or employee or agent of the Commission who fails without
just cause to comply with a requirement of an auditor in terms of subsection (1)
shall be guilty of an offence and liable to a fine not exceeding one thousand
dollars or to imprisonment for a period not exceeding three months or to both
such fine and such imprisonment.

PART VI
LEVIES

32 Imposition of levies
(1) Subject to this part, the Commission with the approval of the Minister may by
notice in a statutory instrument impose one or more levies on licenses.
(2) in a statutory instrument referred to in subsection (1), the Commission may
prescribe –
(a) the persons responsible for the payment of the levy; and
(b) the persons responsible for the collection and remittal of the levy; and
(c) the manner and times at which the levy shall be paid, collected and remitted;
and
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 (d) the imposition of interest and additionally, or alternatively, a surcharge if levy
is not paid within the time prescribed; and
(e) the books and records to be kept and the returns and information to be
furnished to the Commission or any other person for the purpose of the levy.

(3) Any statutory instrument made in terms of this section shall be laid before
Parliament as soon as may be after it has been published and, if a resolution is
passed within the next fourteen days on which Parliament has sat next after the
statutory instrument is laid before it requesting the Commission to rescind or
vary the statutory instrument, it shall forthwith be rescinded or varied, as the
case may be, by further statutory instrument but without prejudice to the validity
of anything previously done thereunder.

33 Withdrawal, suspension or increase of levies

Without derogation from section 21 of the Interpretation Act [Chapter 1:01], the
Commission, with the approval of the Minister, may by notice in statutory instrument –
(a) Withdraw any levy; or
(b) Suspend any levy in whole or in part; or
(c) Increase the rate or incidence of any levy:
Provided that subsection (3) of section thirty-two shall apply to a statutory instrument
increasing the rate or incidence or any levy.

34 Recovery of unpaid levies

A levy and any interest or surcharge connected therewith shall be a debt due to the
Commission and any amount of levy or of any such interest or surcharge thereon that is
not paid, collected or remitted may be recovered by the Commission by proceedings in
a court of competent jurisdiction.

PART VII
MISCELLANEOUS PROVISION RELATINF TO COMMISSION

35 Minister may give policy directions

The Minister may give directions to the Commission relating to the policy the
Commission has to observe in the exercise of its functions including, in particular
directions relating to tariffs chargeable by licensees.
36 Execution of contracts and instruments by Commission

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 Any agreement, contract or instrument approved by the Commission may be entered
into or executed on behalf of the Commission by any persons generally or specially
authorized by the Commission for that purpose.
37 Reports of Commission
(1) In addition to any report which the Commission is required to submit to the
Minister in terms of this Act or the Audit and Exchequer Act [Chapter 22:03],
the Commission –
(a) shall submit to the Minister such other reports as the Minister may require; and
(b) may submit to the Minister such other reports as the Commission considers
advisable.
(2) The Minister shall, within six months of the end of the Commission’s financial
year, lay before Parliament a report submitted to him by the Commission in
terms of subsection (1), together with the statement of accounts and auditor’s
report for the preceding financial year of the Commission referred to in sections
twenty-nine and thirty.
38 Staff of Commission
(1) The Commission shall employ such persons as it considers expedient for the
better exercise of its functions.
(2) The Commission may assign to its staff such of its functions as the Commission
thinks fit.
(3) Any assignment of functions in terms of subsection (2) may be made either
generally or specially and subject to such reservations, restrictions and
exceptions as the Commission may determine, and may be revoked by the
Commission at any time.
(4) Anything authorized or required by or under this Act to be done by the
Commission, other than the making of an order in terms of subsection (3) of
section fifty, may be done by any member of the staff of the Commission who
has been authorized either generally or specifically by the Commission for that
purpose.

39 Exemption from liability for Commission

No liability shall attach to the Commission or to any employee of the Commission or to
a Commissioner for any loss or damage sustained by any person as a result of the

45 Restrictions of licensees
(1) A licensee shall not assign or cede his licence or transfer his electricity
undertaking, or any part thereof, by way of sale, mortgages, lease, exchange or
otherwise, without the prior consent of the Commission.

21
 Provided that, should the Commission determine that in any instance the circumstances
so require, it may establish license terms and conditions providing its specific or
general consent for any or all of the foregoing.
(2) No license shall without the prior written consent of the Commission, acquire
by purchase or otherwise, or affiliate with, the license or undertaking of any
other licensee or person that is in the business of electricity generation,
transmission, distribution or supply:
Provided that the Commission may as part of its consent impose conditions such as, but
not limited to, adherence to any code of conduct.

46 Licence applications
(1) An application for a licence shall be made to the Commission in the form and
manner prescribed and be accompanied by the prescribed fee, if any, and such
information or documents as may be prescribed or and it may require, including
information concerning any tariff required in terms of section fifty-three.
(2) An applicant for a licence who is an affiliate of a body corporate which has
applied for or holds another such licence shall disclose such interest to the
Commission in his application.
(3) For purposes of subsection (2), an “affiliate of a license” includes a generating
company outside Zimbabwe that is entitled, under an arrangement approved by
the Commission or permitted by a licence issued to another licensee, to sell
power to Zimbabwean licensees or consumers without a licence from the
Commission.
(4) Deemed licensees shall submit applications for licences to the Commission
within one year of the appointment of the Commission or such later date as may
be determined by the Commission for any one or more deemed licensees:
Provided that the Commission may not extend the date for any such application to a
date later than two years from the effective date of this Act.
(5) Subject to subsection (7), if on consideration of an application in terms of
subsection (1), the Commission is satisfied that –
(a) The applicant will comply with such of the provisions of this Act and any codes,
standards, regulations and licence terms and conditions as apply to the
electricity service or electric power system he intends to provide or operate; and
(b) The grant of the licence does not infringe the rights of a prior licensee and
(c) The grant of the licence is in the public interest or, in the case of an applicant
referred to in subsection (2), the grant of the licence is not detrimental to the
public interest;
The Commission shall issue the appropriate licence to the applicant.
(6) Within thirty days after the issue of a licence referred to in subsection (5) the
licensee shall, at his own expense, cause the licence to be published in a newspaper
circulating in the area in which he intends to operate as a licensee.
22
 (7) If, on consideration of an application in terms of subsection (1), the Commission is
not satisfied as to the matters referred to in subsection (5), it shall refuse to issue a
licence to the applicant concerned:
Provided that –
(a) Before refusing to issue a licence on the ground that it is not satisfied as to the
matters referred to in subsection (5), the Commission shall notify the applicant in
writing that it proposes to refuse the application and of its reasons for doing so, and
shall afford the applicant an adequate opportunity to make representations in the
matter;
(b) Within ten days after deciding to refuse to issue a licence on any ground, the
Commission shall notify the applicant in writing of its decision and of the reasons
for it.

(8) The period between the Commission’s receipt of an application in terms of

subsection (1) and all documents and information submitted in support of it, and the
date on which it notifies the applicant of its decision or proposed decision in terms
of subsection (5) or (7), as the case may be, shall not exceed six months unless the
applicant consents to an extension of the period.

(9) Notwithstanding subsections (1) to (7) of this section, the Commission may
establish simplified procedures for undertakings and businesses that are limited in
size and scope so as to expedite the application and licensing process.

47 Terms and conditions of licences

(1) A licence shall be issued subject to such terms and conditions as may be
prescribed or as the Commission may reasonably determine in the
circumstances, such as the size and service of the undertaking or business,
whether it is to be a monopoly or competitive service, whether the service is to
be provided pursuant to a contract between the parties and whether the service is
to be provided to a consumer or to another licensee:
Provided that in the case of a licensee whose services are provided pursuant to a
contract, such as power purchase agreement, the Commission may incorporate in the
licence the contractual obligations of the licensee or declare the terms and conditions of
the contract to be the terms and conditions of the licence or part thereof.

(2) In the case of a licence issued to an applicant referred to in subsection (2) of section
forty-six, the licence may be issued subject to the condition that the licensee shall
divest himself within a specified time of any holding of shares in another licensee
or such other conditions, including adherence to any code of conduct, that the
Commission determines to be in the public interest.
(3) In issuing or renewing a distribution licence, the Commission may impose a
condition requiring the licensee to make such reasonable provision as may be
specified by the Commission in the licence for the facilitation of rural electrification
in the proximity of the service.

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 (4) Without derogation from the generality of subsection (1), the terms and conditions
of a licence may require the licensee to –
(a) Enter into agreements on specified terms with other persons for the provision of
or use of electric lines and associated equipment operated by the licensee;
(b) Purchase power and other resources in an economical and transparent manner;
(c) Refer disputed for arbitration, mediation or determination by the Commission.

(5) A licence may require the licensee to provide information on a periodic basis, in
such form and detail as the Commission may determine.

(6) Unless expressly indicated in the licence, the grant of a licence shall not hinder or
restrict the grant of a licence to another person for a like purpose and, in the absence
of such express indication, the licensee shall not claim any exclusivity:
Provided that the Commission may allow a licensed activity to be exclusive for all or
part of the period of the licence, for a specific purpose for a geographical area, or for
any combination of the foregoing.
(7) A licence may contain terms and conditions for the licence to cease to have effect or
to be modified or amended by the Commission in such circumstances as may be
specified in the licence or as may be determined by the Commission.

(8) As a condition of its licence every licensee shall, unless expressly exempted by its
licence, prepare and submit to the commission each year an annual statement of
accounts in such form, and containing such particulars, as the Commission may
require.

(9) The Commission shall include in each licence such details as it determines are
required regarding the rights and obligations of the licensee, and their devolution at
the end of its licence term.

(10) A licence shall be valid for a period of up to, but not exceeding, thirty years, as
may be determined by the Commission:
Provided that the Commission may extend the period of a licence, taking into account
the nature of the undertaking or business for an additional period not exceeding twenty
years should it determine that it is in the public interest to do so.

48 Renewal of licences
(1) Subject to this Act, the holder of a licence may apply for its renewal before it
expires.
(2) An application for the renewal of a licence shall be made to the Commission in
the form and manner and within the period prescribed and be accompanied by
the prescribed fee, if any.

49 Amendment of licences
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 (1) Subject to this section, the Commission may at any time amend a licence or any
term or condition of a licence –
(a) to correct any manifest error in the licence; or
(b) If the licensee requests the amendment; or
(c) if the amendment is pursuant to a condition of the licence imposed in terms of
subsection (7) of section forty-seven or subsection (5) of section fifty-one.

(2) Where a licensee makes an application for the amendment of his licence, he
shall publish a notice of the proposed alterations or amendments to his licence
in the period within which objections or representations in connection with the
amendments may be made to the Commission and the Commission shall not
amend any licence until all objections received by it have been considered.
(3) In the case of an application proposing alterations or amendments to a licence of
a licensee who provides services to an area covering a cantonment aerodrome or
camp oar any building or place occupied by the Government for defence
purposes, the Commission shall obtain the consent of the government before
making the alteration or amendment to the licence.
(4) Before making an alteration or amendments in a licence otherwise than in terms
of paragraph (a) or (b) of subsection (1), the Commission shall publish the
proposed alterations or amendments stating the period within which objections
or representations may be made to the Commission and the Commission shall
consider all such objections or representations.

50 Enforcement of licences
(1) Without derogation from its powers in terms of section fifty-one, where the
Commission is satisfied that a licensee is contravening, has contravened or is
likely to contravene any of the conditions of his licence, the Commission may
serve upon the licensee an order –
(a) requiring the licensee to do, or not to do, such thinks as are specified in the
order for the purpose of rectifying or avoiding any contravention or threatened
contravention of any condition of the licence; and
(b) stipulating the period within which any requirement referred to in paragraph (a)
shall be commenced and completed; and notice of the order shall be published
by the Commission in such manner as it considers appropriate to draw the
attention of other persons affected or likely to be affected by the contravention
or threatened contravention of the licence.
(2) Before serving an order in terms of subsection (1), the commission shall serve a
notice upon the licensee concerned –
(a) specifying the grounds upon which the order is to be issued and what the
Commission considers is required for the purpose of rectifying or avoiding any
contravention or threatened contravention of any condition of the licence; and
25
 (b) stipulating the maximum period that the Commission considers reasonable for
the implementation of any requirement it proposes to order; and
(c) calling upon the licensee, if he wished to make representations, to make them
to the Commission within such period from the date of service of the notice as it
shall specify.
(3) After considering any representations made in terms of paragraph (c) of
subsection (2), the Commission may serve an order on different terms.
(4) An order served in terms of subsection (1) may specify a penalty for each day that
the licensee subjected to the order is in default of compliance with the order not
exceeding the period and amount prescribed.

(5) The obligation to comply with an order served in terms of subsection (1) is a duty
owed to any person who may suffer loss or damage by a contravention of it.

(6) Civil proceedings for specific performance, an interdict, damages, the recovery of
any penalty imposed in terms of subsection (4) or other appropriate relief in respect
of any contravention or threated contravention of any order served in terms of
subsection (1) may be brought against the license concerned by the Commission
and additionally, or alternatively by any person referred to in subsection (5).

(7) The amount of any penalty imposed in terms of subsection (4) shall form part of the
funds of the Commission.

51 Cancellation of licences
(1) On its own initiative or upon receiving a complaint from –
(a) any consumer of electricity services, association of such consumers or
association of traders or industrialists;
(b) any company or person involved in the generation, transmission, distribution or
supply of electricity;
The Commission may inquire into the conduct or functioning of any licensee in
carrying out his obligations under the Act or regulations made in terms of section sixty-
five or the terms and conditions of his licence.
(2) Subject to subsection (3), the Commission may, after an inquiry, whether or not
conducted in the form of hearing in terms of Part IV, cancel any licence if in its
opinion –
(a) the licence was issued through fraud or the misrepresentation or non-disclosure
of a material fact by the licensee; or
(b) the licensee has willfully or unreasonably contravened any provision of this Act
that is applicable to him; or

26
 (c) the licensee has failed to comply with any term or condition of the licence, the
breach of which is expressly declared by such licence to render it liable to
cancellation; or
(d) the financial position of the licensee is such that he is unable to fully and
efficiently discharge the duties and obligations imposed on him by his licence.
Provided that the Commission must, before deciding to cancel the licence in terms of
this paragraph, determine that the licensee will not be able to resolve its financial
problems within a reasonable time, given the circumstances.

(3) Before cancelling a licence in terms of subsection (1), the commission shall
notify the licensee in writing of its intention to cancel the licence concerned and
the reasons for doing so, and may allow the licensee an opportunity to make
representations in the matter or to demonstrate that circumstances have, changed
do that cancellation may no longer be warranted.
(4) if, at the conclusion of the inquiry in terms of subsection (2), the Commission is
satisfied for any reason specified in subsection (2) that it is in the public interest
the licence concerned should be cancelled, the Commission may by notice in
writing to the licensee, cancel the licence or proceed in terms of subsection (5)
or take such other action as it considers appropriate.
(5) instead of cancelling a licence, the Commission may allow the licence to
remain in force subject to such further terms and conditions as it may deem
necessary to impose and such terms and conditions shall form part of the
licence.
(6) in the event that the Commission decides to cancel a licence, it shall serve on
the licensee a notice of cancellation fixing the date on which the cancellation
shall take effect and the commission shall make such interim arrangements in
regard to the undertaking of the licensee for maintaining continuity in the
provision of its electricity service as the Commission may consider appropriate.

52 Pricing methodology and accounting procedures

(1) The Commission shall prepare a pricing methodology for use by the
Commission in setting prices and accounting procedures that licensees will use
when providing financial and other information to the Commission.

(2) In preparing the pricing methodology and accounting procedures referred to in

subsection (1), the Commission shall –
(a) Consult licensees, The Rural Electrification Fund Board, The Zambezi River
Authority and such persons as it considers necessary or expedient to consult.
(b) Obtain evidence, information or advice from any person who, in the
Commission’s opinion, possesses expert knowledge which is relevant in the
preparation of the methodology or procedures.

27
 (3) On completion of the pricing methodology and accounting procedures referred
to in subsection (1), the Commission shall give notice in the Gazette and in a
newspaper with wide circulation, of the places at which the pricing
methodology and accounting procedures will be publicly exhibited and the
period, not being less than thirty days after the publication of the notice in the
Gazette within which objections or representations in connection with the same
may be made to the Commission.

(4) If, after the period specified in a notice in terms of subsection (3) –
(a) No objections or representations have been received in response to the
notice, the, Commission may confirm the pricing methodology and the
accounting procedures referred to in subsection (1); or
(b) Objections or representations have been received in response to the notice,
the Commission shall consider all the objections and representations and
may either –
(i) Confirm the pricing methodology and accounting procedures
referred to in subsection (1); or
(ii) Carry out such further consultations as it considers necessary.
(5) The Commission shall fix the date on which the pricing methodology and the
accounting procedures referred to in subsection (1) shall come into operation
and it shall cause notice to be given in the Gazette of that date.

(6) If it appears to the Commission that the pricing methodology or accounting

procedures that have come into operation in terms of subsection(5) should be
materially changed, the Commission shall give notice in the Gazette and in a
newspaper with wide circulation of the proposal to change the methodology or
accounting procedures and of the places at which the proposed changes are
exhibited and the period, not being less than thirty days after the publication of
the notice in the Gazette, within which objections or representations in
connection with the proposal may be made.

(7) After taking into account any objections or representations received in response
to a notice in terms of subsection (6), the Commission may confirm the
proposed changes to the methodology or accounting procedures and shall
thereafter incorporate such changes.

(8) Every person upon whom any function has been conferred or imposed in
connection with setting process and tariffs and submitting information to the
Commission shall be bound by pricing methodology or accounting procedure
that has come into operation in terms of subsection (5).

53 Electricity tariffs and prices

(1) No prices or tariffs in connection with the provision of an electricity service or
operation of an electric power system by a licensee or proposed licence shall have
effect unless such prices or tariffs have been approved or, in the case of any service

28
 determined by the Commission after consultation with the Minister, fixed by the
Commission in terms of this section.

(2) An application for the fixing or approval of prices and tariffs shall be made by a
licensee or proposed licensee to the Commission in the form and manner prescribed
or together with the application for the licence, as the case may be.

(3) The Commission shall, subject to the following principles, fix or approve prices and
tariffs for licensees with a view to –
(a) Enabling an efficient licensee to recover the full costs of its business activities,
including a reasonable return;
(b) Providing incentives for the continued improvement of the technical and
economic efficiency with which the services are provided;
(c) Protecting consumers while keeping them informed about the cost their
consumption imposes on the licensee’s business;
(d) Avoiding undue discrimination between customers and customer categories
(e) Phasing out or substantially reducing costs subsides.

(4) The application of the principles in subsection (3) shall not preclude the
Commission from allowing a lifeline tariff for some customers.

(5) The Commission shall take into account any subsidy provided by the Rural
Electrification Fund or from any other source, whether direct or by way of
favorable financing terms or in any other manner, in the fixing or approving of
prices and tariffs.

(6) Notwithstanding subsection (3), the Commission shall have the authority to approve
prices and tariffs that are established pursuant to the terms and conditions of a
contract between licensees or between a licensee and one or more customers.

(7) For the purposes of subsection (6) “prices and tariffs that are established pursuant to
a contract” includes methods and formulas which allow for the calculation of prices
and tariffs.

(8) Notwithstanding paragraph (d) of subsection (3), in fixing or approving prices and
tariffs the Commission may differentiate among consumers on the basis of
differences in total electricity consumption, the time periods on which electricity is
consumed, load factor, power factor, voltage levels and other such criteria as affect
the cost of providing a service.

(9) Any fines or penalties levied against a licence in terms of this Act or any other law
or regulation shall not be chargeable to the licensee’s customers.

(10) An applicant for approval of prices and tariffs shall publish notice of his
application in a manner to be determined by the Commission and the applicant shall
publish notice of the prices and tariffs approved by the Commission in such manner
as the Commission may determine.

29
 (11) Every licensee shall keep at his office a current copy of the prices and tariffs as
approved by the Commission and make a copy available for inspection on request
by any person free of any charge during the licensee’s normal working hours.

(12) The Commission shall render its decision on an application for tariff’s within
four months of the date of the application unless the applicant consents to a longer
period.

54 Special provisions relating to transmission and distribution licensees

(1) Subject to this section and to such exceptions or conditions as the Commission
may include in the relevant licence, the Commission may apply any of the
provisions of the Second Schedule to a transmission or distribution licensee:
Provided that the licensee concerned shall not be released from any duty attaching
to or connected with any right or power so applied.

(2) The Commission shall not act in terms of subsection (1) unless it is satisfied
upon representations made by the licensee or proposed licensee concerned that
the electricity transmission or distribution concerned is not otherwise
practicable.

(3) Without derogation from the generally of subsection (1), the exceptions and
conditions there mentioned shall include such exceptions and conditions as
appear to the commission to be necessary or expedient for the purpose of
securing-

(a) That the physical environment is protected;

(b) That there is no greater damage to streets or interference with traffic that is
reasonably necessary;
(c) That funds are available for meeting any liabilities which may arise from the
exercise of any rights or powers applied in terms of subsection (1).

(4) Any person who is aggrieved by any decision of the Commission made in terms
of subsection (1) may appeal against such decision in terms of section sixty-
four.
55 Use of certain conduits for electricity purposes
(1) in this section-
“authority” includes a local authority and statutory body;
“conduit” includes a tunnel or subway;
“relevant conduit” means –

30
 (a) A water main or any other conduit maintained by a water authority for the
purpose of conveying water from one place to another; or
(b) A public sewer

(2) The functions of an authority with control of a relevant conduit shall include the
power –
(a) To carry out, or to authorize any person to carry out, any works in relation to
that conduit for or in connection with the installation, maintenance
adjustment, repair or alteration of apparatus for purposes connected with the
transmission or distribution of electricity; and
(b) To keep the electricity apparatus installed in that conduit or to authorize any
other person to keep that apparatus so installed; and
(c) To authorize any person to enter that conduit to inspect electricity apparatus
kept installed there; and
(d) To enter into agreements on such terms, including terms as to the payments
to be made to the authority, as it thinks fit, in connection with the doing of
anything authorized by or under this section; and
(e) To carry on an ancillary business consisting in the making and carrying out
of agreements.

(3) Where any enactment expressly or implied imposes any limitation on the use to
which a relevant conduit may be put, that limitation shall not have effect so as
to prohibit the doing of anything authorized by or under this section.

(4) Where the doing by an authority with control of a public sewer of anything
authorized by this section would, apart from this subsection, constitute a
contravention of any obligation imposed (whether by virtue of any conveyance
or agreement or otherwise) on a licensee, the doing of that think shall not
constitute such a contravention to the extent that it consists in or in authorizing,
the carrying out of works or inspections, or keeping of apparatus, wholly inside
a public sewer.

(5) Subject to subsections 93) and (4), subsection (2) is without prejudice to the
rights of any person with an interest in land on, under or over which a relevant
conduit is situated.

56 Notice of Construction of Railways and Telecommunication Works and Control of

other works

(1) Any person who desires to construct or extend any railway or any works for
telecommunications shall –
(a) Give one month’s notice in writing to the Commission of his intention to
commence such construction or extension; and

31
 (b) Furnish the Commission with a plan of the proposed railway or works, together
with the particulars showing the manner and position in which the railway or
works are intended to be constructed or extended and carried on and such
further information as the Commission may require:
Provided that this subsection shall not apply to the construction or extension of such
railway r telecommunication works as may be prescribed.

(2) If it appears to the Commission that –

(a) The operation of or the equipment to be used in connection with a railway or
works referred to in subsection (1) is likely to affect injuriously or interfere with
the work or maintenance of electricity lines or the carrying on by a licensee of
an electric power system; or
(b) Any electricity line is being affected injuriously or interfered with by the
construction or operation of or the equipment used in connection with –
(i) A railway or work referred to in subsection (1); or
(ii) Any railway works or other operations whatsoever;
The Commission shall notify in writing the person constructing or operating the railway
or works of the action which that person is required to take in order to remedy or
prevent the injury or interference.
(3) A person referred to in subsection (2) who, after receipt of a notice in terms of that
subsection, proceeds with the construction or operation of the equipment concerned
or continues to operate the railway or works without complying with the terms of
that notice shall be liable for all loss and damage caused to any licensee by his
failure to comply with the terms of that notice.

PART IX
CONSUMER PROTECTION AND LICENSEE PERFORMANCE STANDARDS

57 Consumer Protection Standards

(1) The Commission shall require licenses to develop and submit to the
Commission for its review, the following –
(a) Customer service standards;
(b) Customer complaint handling standards and procedures;
(c) Codes of practice for the provision of assistance to special – needs
customers, such as the blind, disabled , elderly or severely ill;
(d) Procedures for applying for an electricity service;
(e) Procedures for disconnection non-paying customers or customers in breach
of any other terms and conditions of an applicable tariff or contract;
(f) The information to be provided to consumers and the manner of its
dissemination.

32
 (2) The Commission may develop model consumer protection standards providing
for the matters referred to in subsection (1), and if so, shall refer such model
standards to the Rural Electrification Fund Board for its comments and to any
other persons it considers necessary or expedient to consult.

(3) Model standards shall be published in such manner as the Commission deems
fit.

58 Performance standards and codes

(1) The Commission shall require every licensee to develop and submit to the
Commission for its review the following –
(a) Standards of overall performance in connection with the provision of
electricity supply services and in connection with promotion of the efficient
use of electricity by consumers;
(b) Such grid codes, technical codes and manuals as may be required for the
safe, reliable and efficient operation of the electric power system of the
licensee;
(c) Such other standards, codes or manuals as the Commission may require.

(2) The Commission may develop model standards, codes and manuals in relation
to the matters referred to in subsection (1) and shall refer such model standards,
codes and manuals to the Rural Electrification Fund Board for its comments,
and to any other persons it considers necessary or expedient to consult.

(3) Model standards, codes and manuals shall be binding on licensees and shall be
published in such manner as the Commission deems fit.

(4) Different standards, codes or manuals may be determined for different licensees
under this section.

PART X
COMPETITION AND MARKET POWER

59 Regulated Services: Competition and Market Power

(1) The Commission shall have the ongoing responsibility to monitor whether
electricity services are being provided competitively, and in particular shall
determine whether any electricity service in respect of which prices or tariffs are
fixed by the Commission in terms of section fifty-three (hereafter in this section
referred to as a “regulated services”) can be provided competitively, and to
provide a report on these matters, at least annually to the Minister.
(2) Upon a finding by the Commission that it is in the public interest that a
regulated service should be freed from price or tariff regulation by the
33
 Commission, the Commission may, subject to the approval of the Minister,
determine when and under what circumstances such service should be
deregulated:

Provided that nothing this section shall be construed to exempt such service from
being licenses in terms of this Act.

(3) This section shall not be construed to limit the Commission’s authority to
determine whether to restrict the introduction of competition to certain
geographical areas or to certain licensees or customers on a temporary or
permanent basis.

(4) Notwithstanding a determination that a regulated service can be provided

competitively, the Commission may require that default service in terms of this
Act continue to be offered by a licensee on a regulated basis.

(5) The Commission shall determine the pre-conditions and nay transitional
arrangements required for a regulated service to be offered competitively,
including, but not limited to, codes of conduct, rules regarding access to
information, access to the electric system, and constrains against undue price
discrimination in the offering of services.

(6) The Commission shall have the ongoing responsibility to monitor electricity
undertakings and markets to determine whether there is, or may be, market
power, for which purpose the Commission shall be entitled to –

(a) Require information from licensees;

(b) Undertake inquiries and hearings;
(c) Establish or contract with an independent entity to provide monitoring
services for the purpose of this subsection.

(7) The Commission shall be required to provide to the Competition and Tariff
Commission any information or evidence of the presence of or the possible
development of, market power in the operation of the licensed undertakings or
electricity markets.

(8) In the event that the Commission determined that there is any problem related to
the development or unfair exercise of market power, it may –
(a) Issue such cease and desist orders as may be required upon the license or
licensees concerned;
(b) Levy monetary penalties upon the licensee or licensees concerned;
(c) Refer the matter to the Competition and Tariff Commission for
investigation:
Provided that the Commission shall not utilize its powers in terms of paragraphs (a) or
(b) except with the concurrence of the Competition and Tariff Commission.

34
 (9) The Commission shall have the ongoing responsibility to consider issues
associated with the competitive provision of electricity services and the
prevention or mitigation of market power in its decisions and orders regarding
matters such as but not limited to, licence applications, the grant of licences,
licence terms and condition, the setting of prices and tariffs, and whether or not
to approve a merger acquisition or affiliation.

PART XI
OFFENCES

60 False statements and declarations

Any person who, before the Commission or in any application for a licence under this
Act, makes any statement which he knows to be false or does not have reasonable
grounds to believe to be true, shall be guilty of an offence and liable to a fine not
exceeding tem thousand dollars or to imprisonment for a period not exceeding six
months or to both such fine and such imprisonment.

61 Other offences
(1) Any person who –
(a) Fails or refuses to furnish a return or to supply information in the manner
and in the time prescribed or furnishes a false or incomplete return or
supplies false or incomplete information; or
(b) Willfully delays or obstructs an inspector or police officer in the exercise of
the powers or duties conferred or imposed upon him by or under this Act or;
(c) Fails or refuses, without reasonable cause to give information to an
inspector or a police officer when required to do so in terms of section sixty-
two or gives false or incomplete information; or
(d) Fails to comply with any requirement contained in a notice served on him in
terms of section sixty-two or with a requirement made by an inspector or
police officer in terms of that section; or
(e) Willfully destroys, injuries or removes the equipment or apparatus of a
licensee; or
(f) Contravenes subparagraph (1) of paragraph 10 of the Second Schedule;
Shall be guilty of an offence and liable to a fine not exceeding fifty thousand dollars or
to imprisonment for a period not exceeding two years or to both such fine and such
imprisonment.

62 Inspections
(1) The Commission may appoint persons employed by it to be inspectors for the
purposes of this Act and shall furnish each person so appointed with a certificate
stating that he has been appointed as an inspector.
35
 (2) An inspector shall, in addition to any other functions that may be assigned to
him by the Commission, be responsible for inspecting electricity undertakings
to ensure the safety of operations and to investigate accidents.

(3) Subject to subsection (9), an inspector or police officer may at all reasonable
times enter premises –

(a) Of a licensee; or
(b) On which he has reasonable cause to suspect an offence against this Act has
been committed;
and shall have power to make such examination, inspection and inquiry and do such
things as may appear to him necessary for ascertaining whether compliance has been
made with this Act.
(4) Subject to subsection (6), all books, records, accounts and documents required
to be kept by a licensee in terms of this Act shall be open to inspection at all
reasonable times by an inspector or by a police officer.

(5) Subject to subsection (6), an inspector may inspect at all reasonable times any
generating station or equipment or apparatus or premises worked or used by or
in the possession or under the control of a licensee.

(6) The powers of entry and inspection conferred by this section shall only be
exercised with the consent of the person in charge of the premises concerned,
unless there are reasonable grounds for believing that it is necessary to exercise
them for the prevention, investigation or detection of an offence in terms of this
Act or for the obtaining of evidence relating to such an offence, or for the
prevention or curtailment of conditions that may have an adverse effect on
public health or safety.

(7) An inspector or police officer may, in exercise of the powers conferred upon
him by this section, seize any equipment, apparatus, book, record or document
which he has reasonable cause to suspect will afford evidence of the
commission of an offence against this Act and may retain it for so long as may
be necessary for the purpose of any examination, investigation, trial or inquiry.

(8) An inspector may, in the exercise of the powers conferred upon him by this
section, order a person referred to in subsection (5) to cease any activity,
pending inquiry by the Commission, which is not in accordance with this Act
or, as the case may be, the terms and conditions of his licence.

(9) An inspector shall, on demand by any person affected by the exercise of the
powers conferred upon him by this section, exhibit the certificate issued to him
in terms of subsection (1).

63 Dispute Resolution
36
 (1) In the event of a dispute between licensees, the parties shall attempt to resolve
the dispute themselves.

(2) Where the licensees fail to resolve their dispute, one or more of the parties to
the dispute may petition the Commission providing relevant documentation
concerning-

(a) The issues in dispute; and

(b) The position of each of the parties with respect to these issues; and
(c) The areas of agreement between the parties, if any.

(3) The other parties to the dispute shall be afforded an opportunity by the
Commission to respond to the petition and to provide any other information
which may assist in the resolution of the dispute.

(4) The Commission, after holding a hearing on the dispute in terms of Part IV,
shall make its determination in the matter.

64 Appeals
(1) Subject to this section, any person who is aggrieved by –
(a) A decision of the Commission not to issue a licence; or
(b) Any term or condition of a licence issued to him, or a refusal by the
Commission specify a term or condition in a licence; or
(c) A refusal by the Commission to renew a licence; or
(d) Any amendment of a licence or a refusal by the Commission to amend a
licence; or
(e) The cancellation of licence; or
(f) The grant or refusal by the Commission to rant any approval or authority in
terms of this Act; or
(g) The determination of disputes between licenses by the Commission or
(h) A decision of the Commission with respect to prices or tariffs; or
(i) Any other decision of the Commission;
may appeal to the Administrative Court.

(2) For the purpose of determining an appeal noted in terms of subsection (1); the
Administrative Court may require the Commission to furnish it with the reasons
for the decision or action that is the subject of the appeal and a copy of any
evidence upon which the reasons are based.

(3) An appeal in terms of subsection (1) –

(a) Shall not have the effect of suspending the decision or order appealed
against;
(b) Shall be made in the form and manner and within the period prescribed in
rules of court.
37
 (4) For the purpose of determining an appeal in terms of subsection (1), the
President of the Administrative Court shall be assisted by two assessors having
ability or experience in the field of electricity.

(5) On an appeal in terms of subsection (1), the Administrative Court may confirm,
vary or set aside the decision or action appealed against and may make such
order, whether as to costs or otherwise as the court thinks just.

(6) Prior to making an appeal in terms of subsection (1), an aggrieved person may,
if the decision or action was taken on the basis of a manifest error, within ten
days or being notified of the decision or action, request the Commission to
reconsider the decision or action.
65 Regulations
(1) The Minister may, after consultation with the Commission, make regulations
prescribing all matters which by this Act are required or permitted to be
prescribed or which, in the opinion of the Commission, are necessary or
convenient to be prescribed for carrying out or giving effect to this Act.

(2) Regulations made in terms of subsection (1) may provide for any or all of the
following-

(a) The administration of the affairs of the Commission including, inter alia, the
manner of holding of meetings, hearings and proceedings, arbitration and
mediation proceedings, the conduct of inquiries and investigations, the rules
by which evidence shall be taken at hearings and generally the conduct of its
business;
(b) The duties, powers, rights and obligations of a licensee;
(c) The procedure for applying for licences and requirements with respect to the
information and documentation too be submitted by applicants;
(d) The procedure for amending or cancelling licences;
(e) The determination of the standards of performance that will be required
from licensees;
(f) The information that will be required from licensees and the manner and
form in which it shall be provided;
(g) The method and manner by which will be determined the prices and tariffs
that may be charged by licensees for their services;
(h) Feed, levies and other charges that may be payable in terms of this Act by
licensees or consumers;
(i) The regulation of investments, assets and properties and the interest in such
assets and properties, held in connection with the electricity industry;
(j) Customer-related matters, such as complain handling procedures, practices
concerning customers with difficulties paying bills and connection and
disconnection procedures;
(k) The resource procurement policies of and the associated contracting by the
licensees, including as may applicable the review and approval of same;
(l) The regulatory treatment of rural electric schemes and investments;
38
 (m)Procedures for addressing licensee mergers, acquisition, affiliate
relationships and transactions related thereto;
(n) Procedures for market power monitoring and mitigation;
(o) The terms and conditions for the provision of system access by transmission
and distribution licensees or entities;
(p) Fines and penalties that may be payable in terms of this Act;
(q) Such other regulations as may be required

(3) Regulations made in terms of subsection (1) may provide for the imposition of
penalties not exceeding five thousand dollars or, in default of payment,
imprisonment for a period not exceeding six months, for any contravention of
the regulations.

66 Disclosure of confidential information and use of information acquired by

inspectors, etc, for personal gain

(1) If an inspector or Commissioner or employee of the Commission in the course of

his duties as such acquires information relating to the financial affairs of any
person, or to any commercial secret, he shall not for personal gain make use of such
information, nor disclose it to any other person except –
(a) For the purpose of legal proceedings under this Act or any other law; and
(b) To the extent that it may be necessary to do so for the purpose of this Act or any
other law, to another inspector or Commissioner or employee of the
Commission.

(2) No inspector or Commissioner or employee of the Commission shall, for personal

gain make use of any information acquired by him in the course of his duties as
such for a period of five years after the date on which he ceased to be an inspector,
Commissioner or employee.

(3) Any person who contravenes subsection (1) or (2) shall be guilty of an offence and
liable to the forfeiture of any proceeds accruing to him on account of the
contravention and to a fine not exceeding five hundred thousand dollars or to
imprisonment for a period not exceeding two years or to both such fine and such
imprisonment.

PART XIII
TRANSITIONAL PROVISIONS AND SAVINGS

67 Interpretation in Part XIII

In this Part –

39
“appropriate successor company” means the successor company to the Authority or, where
more than one successor company is formed, the successor company licensed to operate any of
the services of generation, transmission, distribution and supply carried on by the Authority
immediately before the fixed date or any company formed to undertake the purchase,
manufacture, maintenance and repair of equipment and apparatus used by any such company
as the case may be;
“securities”, in relation to the appropriate successor company includes shares, debentures,
bonds and other securities of the successor company whether or not constituting a charge on
the company’s assets;
“transfer date: means the date fixed by the Minister in terms of subsection (1) o section seventy
or where two or more such dates are so fixed, the first such date.

68 Formation of successor companies

Subject to this section, The Minister shall, not later than six months after the fixed date,
take such steps as are necessary under the Companies Act [Chapter 24:03] to secure the
formation of one or more of the following companies limited by shares which shall be
the successor companies to the Authority –
(a) A company to take over the electricity generation plants of the Authority
(b) A company responsible for transmission infrastructure;
(c) A company responsible for the distribution and supply of electricity;
(d) Such other companies as the Minister may approve to be subsidiaries of any of the
foregoing companies.

69 Initial shareholding in successor companies

(1) All the members of the appropriate successor company on its incorporation shall
be persons nominated by the Minister, with the approval of the President and
shall hold their shares on behalf of the State.

(2) All the shares initially issued to members of the appropriate successor company
on its incorporation shall be held by those members on behalf of the State.

70 Transfer of assets and liabilities of Authority to successor companies

(1) Subject to subsection (2), the Minister in consultation with the Board of
Authority, shall by written notice fix the date on which the assets and liabilities
of the Authority shall be transferred to the appropriate successor company:
Provided that the Minister may fix different dates for the transfer of different assets
and liabilities.
(2) On the relevant transfer date, every asset and liability of the Authority which the
Minister has directed shall be transferred to the appropriate successor company
shall vest in that company.
40
 (3) All bonds, hypothecations, deeds, contracts, instruments, documents and
working arrangements that subsisted immediately before the relevant transfer
date and to which the Authority was a party shall, on and after that date, be as
fully effective and enforceable against or in favor of the appropriate successor
company as if instead of the Authority, the appropriate successor company had
been named therein.

(4) It shall not be necessary for the Registrar of Deeds to make any endorsement on
title deeds or other documents or in his registers in respect of any immovable
property, right or obligation shall cause the name of the successor company to
be substituted, free of charge for that of the Authority on the appropriate title
deed or other document or in the appropriate register.

(5) Any licence, permit or authority held by the Authority under any enactment
immediately before the relevant transfer date shall continue in force on and after
that date as if it had been issued or granted to the appropriate successor
company to which it was transferred, in terms of subsection (3) and may be
amended renewed or terminated accordingly.

(6) Any cause of action or proceedings which existed or was pending by or against
the Authority immediately before the relevant transfer date may be enforced or
continued as the case may be on and after that date by or against the appropriate
successor company in the same way that it might have been enforced or
continued by or against the Authority had this Act not been passed.

(7) Any guarantee or suretyship which was given or made by the Government or
any other person in respect of any debt or obligation of the Authority and which
was effective immediately before the transfer date of the principal debt after that
date in relation to the repayment of the debt or the performance of the
obligation, as the case may be, by the appropriate successor company to which
the principal debt or obligation was transferred.
71 Issue of securities in consideration for transfer of assets
(1) In consideration for the transfer of the assets of the Authority to the appropriate
successor company by virtue of section seventy the successor company, if so
required by the Minister shall issue such securities as the Minister may direct –
(a) To the Minister or a person nominated by the Minister; or
(b) To any person entitled to require the issue of the securities following their
initial allotment to a person referred to in paragraph (a).

(2) Securities issued pursuant to a direction under subsection (1) –

(a) Shall be issued or allotted at such times and on such terms and conditions as
the Minister may direct; and
(b) Shall be regarded as fully paid and treated for the purposes of the
Companies Act [Chapter 24:03] as if they had been paid up by virtue of the

41
 payment to the appropriate successor company of their nominal value in
cash.

(3) Any dividends or other moneys received by the Minister or by any other person
on behalf of the State in right of or on the disposal of any security or right
acquired by virtue of this section shall be paid into the Consolidated Revenue
Fund.

(4) Stamp duty shall not be chargeable under the Stamp Duties Act [chapter 23:09]
–

(a) in respect of any security issued in compliance with a direction under

subsection (1);
(b) where any convertible securities were issued in compliance with a direction
under subsection (1), in respect of the exercise of the conversion rights
attached to any such security.

(5) The Minister shall not-

(a) Give a direction under subsection (1) at a time when the appropriate
successor company has ceased to be wholly owned by the State; or
(b) Exercise any power conferred on him by this section, or dispose of any
security issued or allotted to him pursuant to this section, or dispose of any
right in such a security, except after consultation with the Minister
responsible for finance.
72 Conversion of loans transferred to successor companies
(1) In this section –
“transferred loan” means any moneys lent to the Authority by the State, the
liability to repay which vests in the appropriate successor company by virtue of
subsection (2) of section seventy.

(2) The appropriate successor company, if directed to do so by the Minister shall

issue such securities as the Minister may require -
(a) To the Minister or a person nominated by the Minister; or
(b) To any person entitled to require the issue of the securities following their
initial allotment to a person referred to in paragraph (a);
Up to an amount equal to the amount of any transferred loan.
(3) The issue of securities in terms of subsection (2) shall have the effect of
extinguishing by novation the transferred loan in respect of which the securities
were issued up to the nominal value of the securities.

(4) Subsections (2) to (5) of section seventy shall apply, mutatis mutandis, to the
issue of securities under this section and to the rights of holders of such
securities.
42
 73 Transfer of employees to successor company and conditions of service of
transferred employees

(1) With effect from the transfer date every person employed by the Authority
immediately before that date shall be transferred to the service of the appropriate
successor company on terms not less favorable than those enjoyed by him
immediately prior to his transfer.

(2) Until such time as conditions of service are drawn up by appropriate successor
company –
(a) The terms and conditions of service applicable to employees of the Authority
shall continue to apply to every person transferred to the appropriate successor
company as if every such person were still in the service of the Authority; and
(b) An employee may be permitted to continue to contribute towards a pension he
was contributing to when he was in the service of the Authority.

74 Minister may give direction to Authority

(1) Notwithstanding anything to the contrary in the Electricity Act [Chapter 13:05],
the Minister may give the Board of the Authority directions in writing in order
to ensure the proper transfer of the assets and liabilities of the Authority to the
appropriate successor company and the Board shall without delay comply with
every such direction.

(2) Without derogation from subsection (1), directions given under that subsection
may provide for –
(a) The cessation of all or any of the functions of the Authority and any person;
(b) The termination of any contract entered into between the Authority and any
person;
Provided that no such direction shall authorize the Authority to commit an
unlawful breach of any such contract;
(c) the production of any report and the provision of any information
concerning the conduct of the Authority or the Board of the Authority or
anything done by or on behalf of the Authority or the Board of the
Authority.

75 Successor companies deemed to be licensed

(1) Notwithstanding any other provision of this Act the appropriate successor
company or any subsidiary company formed by it for the purpose shall be
deemed to be the holder of-
(a) a generation licence issued in terms of this Act and authorizing the company
to provide and operate the same generation services and systems that it
provided and operated immediately before the fixed date;

43
 (b) a transmission licence issued in terms of this Act and authorizing the
company to provide and operate the same transmission services and systems
it provided and operated immediately before the fixed date;
(c) a distribution licence issued in terms of this Act and authorizing the
company to provide and operate the same distribution services that it
operated and immediately before the fixed date.

(2) The Commission shall without delay cause the relevant licences to be issued to
the companies referred to in subsection (1) and those licences may be renewed,
amended, suspended or cancelled in all respects as if they had been issued in
terms of Part VIII of the Act.

76 Repeal of Cap.13:05
When the President is satisfied that the assets and liabilities of the Authority have been
transferred to the appropriate successor company and that nothing remains to be done
under this Part he shall, by notice in a statutory instrument, repeal the Electricity Act
[Chapter 13:05]

77 Savings and transitional provisions

(1) Any regulations by laws or notices which, immediately before the fixed date,
were in force under the Electricity Act [Chapter 13:05], shall continue in force
mutatis mutandis, as if they had been made in terms of this Act, and may be
amended or repealed accordingly.

(2) Any licence, certificate, authority or permit which was issued in terms of the
Act referred to in subsection (1) and which has effect immediately before the
fixed date shall continue to have effect, mutatis mutandis, for the remainder of
its period of validity as if it had been issued under the appropriate provision of
this Act.

(3) Any price, levy or surcharge which, immediately before the fixed date was
chargeable within any area in respect of the supply of electricity consumers or
to any particular consumer or any undertaking shall n and after the fixed date
and until alternative provision is made in terms of this Act continue to be
chargeable in respect of the supply of electricity to those or similar consumers
by a license or other undertaking which supplies electricity within the area
concerned.

(4) Whenever on or after the fixed date, the commission approves any price of tariff
of standard prices for the supply of electricity in terms of this Act, the
Commission may direct the undertaking concerned to vary or withdraw any
price, levy or surcharge referred to in subsection (3).

44
 (5) Subject to this Act, any right in or over land or water which, immediately before
the fixed date, vested in any undertaking in terms of the former Act or any
enactment repealed by the former Act shall, on hand after the fixed date,
continue to vest in the undertaking concerned as if it had been acquired in terms
of this Act.

(6) Subject to this Act, any permission granted, direction given or other think
whatsoever made, done or commenced which immediately before the fixed
date, has or was capable of acquiring force and effect in terms of the former Act
shall on and after the fixed date, continue to have, or as the case may be, to be
capable of acquiring force and effect as if it had been granted, given, made,
done or commenced, as the case be in terms of the equivalent provision of this
act.

FIRST SCHEDULE (Section 3)

ANCILLARY POWERS OF COMMISSION

1. To acquire by lease, purchase, or otherwise immovable property and to construct

buildings thereon.

2. To buy, take in exchange, hire or otherwise acquire movable property, including

vehicles, necessary or convenient for the performance of its functions.

3. To maintain, alter and improve property acquired by it.

4. To mortgage or pledge any assets or part of any assets and, with the approval of the
Minister to sell exchange let, dispose of, turn to account otherwise deal with any assets
or part of any assets which are not required for the exercise of its function for such
consideration as the Commission may, with the approval of the Minister determine.

5. To open bank and building society accounts in the name of the Commission and to
draw, make, accept, endorse, discount, execute and issue for the purposes of its
functions, cheques, promissory notes, bills of exchange, bills of lading, securities and
other instruments.

6. To insure against losses, damages, risks and liabilities which it may incur.

7. To enter into contracts and suretyships or give guarantees in connection with the
exercise of its functions and to modify or rescind such contracts or rescind suretyships
or guarantees.

8. With the approval of the Minister, to enter into, renew, cancel or abandon arrangements
with any government or electricity regulating authority, local or otherwise, that may
seem conducive to the exercise of its functions or any of them and to obtain from such
45
 government or authority rights, privileges and concessions which the Commission
thinks desirable to obtain and carry out exercise and comply with such arrangements,
rights, privileges and concessions.

9. With the approval of the Minister, to raise loans or borrow money in such amounts and
for such purposes and under such conditions as may be approved by the Minister.

10. To employ upon such terms and conditions as the Commission may think fit, such
persons as may be necessary for conducting its affairs and suspend or discharge any
such persons.

11. Subject to section 39 of the Audit and Exchequer Act [Chapter 22:03], to pay such
remuneration and allowances and grant such leave of absence and to make such gifts
and pay bonuses and the like to its employees as the Commission thinks fit.

12. To provide pecuniary benefits for its employees on their retirement, resignation,
discharge or other termination of service or in the event of their sickness or injury and
for their dependents and for that purpose to effect policies of insurance, establish
pension or provident funds or make such other provision as may be necessary to secure
for its employees and their dependents any or all of the pecuniary benefits to which this
paragraph relates.

13. With the approval of the Minister to purchase take in exchange, hire and otherwise
acquire land or dwellings for use or occupation by its employees.

14. To construct dwellings, outbuildings or improvements for use or occupation by its

employees on land purchased taken in exchange, hired or otherwise acquired by the
Commission.

15. To sell or let dwellings and land for residential purposes to its employees.

16. With the approval of the Minister, to guarantee loans to its employees or their spouses
for the purchase of dwellings or land for residential purposes, the construction of
dwellings and the improvement of dwellings or land which are the property of its
employees or their spouses.

17. To provide security in respect of loans guaranteed in terms paragraph 16 by the deposit
of securities.

18. With the approval of the Minister to make loans to any employee of the Commission –
(a) For the purpose of purchasing vehicles, tools or other equipment used by him in
carrying out his duties; or
(b) Not exceeding three months’ salary or wages payable to him for any purpose;
on such security as the Commission considers adequate.
19. To do anything for the purpose of improving the skill, knowledge or usefulness of its
employees, and in that connection to provide or assist other persons in providing

46
 facilities for training, education and research and to pay for the aforesaid where
necessary.

20. To provide such service as the Commission considers could properly be provided by
the Commission.

21. With the approval of the Minister to provide financial assistance to any person,
association, organization or institution whose activities are such as to be, in the opinion
of the Commission of benefit to the Commission.

22. Generally, to do all such things as may be necessary, conducive or incidental too the
exercise of the powers and the performance of the functions of the Commission under
this Act or any other enactment.

SECOND SCHEDULE (Section 54)

RIGHTS, POWERS AND DUTIES OF TRANSMISSION OR DISTRIBUTION LICENSEES

Interpretation
1. In this Schedule –
“licensee” means a transmission or distribution licensee referred to in subsection (1) of
section fifty-four.
Compulsory acquisition of rights in or interests over land for transmission or distribution
purposes

2. (1) Subject to subparagraph (3), a licensee may with the approval of the
Commission and the Minister responsible for lands and subject to such conditions as
that Minister may impose, compulsorily acquire any servitude or other interest in or
right over land required –
(a) For the purposes of construction or maintaining a transmission or distribution line
and the buildings and exchanges and other apparatus connected therewith; and
(b) For an access road to a site referred to in paragraph (a) or for the construction and
use of such road; and
(c) Any land or interest in or right over land required for the erection of power lines
and for the maintenance and inspection of such lines.

(2) The Commission and the Minister responsible for lands shall not grant approval in
terms of subparagraph (1) except after consideration of the following reports,
namely –
(a) A report by the licensee concerned that –
(i) The licensee is unable to acquire the land, interest or right upon reasonable
terms by agreement with the owner; and
(ii) It is necessary that the land, interest or right be acquired by the licensee for an
purpose referred to in subparagraph (1); and

47
 (b) A report by the Ministry responsible for the environment made on behalf of the
licensee by a person qualified to make such reports assessing the anticipated impact
on the environment of any works to be undertaken for a purpose referred to in
subparagraph (1) and recommending any measures to be taken to assess, prevent to
minimize such impact.

(3) Parts III, V, and VIII of the Land Acquisition Act [Chapter 20:10] shall apply,
mutatis mutandis, to the exercise by a license of his powers in terms of
subparagraph (1).
Use of buildings and structures to support transmission/ distribution lines, etc.
3. (1) Subject to this paragraph, a licensee may on one month’s written notice to the
owner or occupier of the building or structure concerned, attach wires, stays or any
other kind of support to any building or other structure for the purpose of
facilitating or constructing a transmission or distribution line.

(2) If the owner or occupier of any land objects to the exercise of the powers
referred to in subparagraph (1), he may lodge written notice of his objection and his
reasons therefore with the licensee concerned and on receipt of such objection, the
licensee shall refer the matter to the Commission, whose decision shall be final.
Provided that an objection shall be lodged within one month of receipt of the notice
given in terms of subparagraph (1).
(3) Before making any decision or order in terms of subparagraph (2), the
Commission shall give to all partied concerned a reasonable opportunity of making
representation, either in person or in writing.
(4) Before carrying out any work under, over or along any land reserved for railway
purposes, other than maintenance and repair work, a licensee shall give notice in
writing to the National Railways of Zimbabwe of the work he intends to carry out.
Entry upon land for transmission or distribution purposes
4. When in accordance with this Schedule, a licensee has been permitted to occupy or use
any land or has placed a transmission or distribution line in position, he shall be entitled
to reasonable access to such land or line for the purpose of carrying on his operations
on the land or of maintaining, removing, repairing or replacing the line.

Removal of transmission or distribution lines

5. (1) If it necessary to alter or remove a transmission or distribution line owing to any
work or operations on the part of the State or a local authority or other person, the cost
of the alteration or removal shall be borne by the State or the local authority or other
person concerned.

(2) If a building is about to be erected on any land and any transmission or distribution
line passing under or over the land will interfere with building operations, the licensee

48
 concerned shall, within one month of being required in writing to do so, undertake such
alteration or deviation of the line as may be necessary to remove the interference.

(3) If a licensee is satisfied that any alteration or deviation of a transmission or

distribution line that is desired for any reason, other than that mention in subparagraph
(2), is possible, necessary or expedient, the licensee shall within one month of being
required in writing to do so, undertake the alteration or deviation and the cost of
carrying out any such alteration or deviation shall be borne by the person at whose
request it is made.

(4) If by reason of –
(a) Any excavation, blasting, mining or quarrying operations; or
(b) Deposits of mining debris or the making of drains, railways or other cuttings or any
other operations; or
(c) Fumes or effluent from any factory or other such premises; or
(d) The construction of any dam;
any transmission or distribution line is damaged or, in the opinion of the licensee who erected
it, the safety or stability of any line is endangered or likely to be adversely affected, the
licensee may repair, deviate or alter the line and the cost of such repair, deviation or alteration
shall be borne by the person by whom or on whose behalf the operations referred to in
paragraph (a) or (b) were conducted or the premises referred to in paragraph (c) were operated
or the dam was constructed as the case may be.
Provided that where the alterations or deviations which are necessary of expedient are in the
opinion of the licensee, extensive, the licensee may charge the person concerned such
proportion of the cost of the alteration or deviation as the licensee, with the consent of the
Commission, considers fair or reasonable.

Erection of gates for access to transmission or distribution lines

6. (1) If a fence on any land, including state land makes it impossible or inconvenient
for a licensee to gain access to his transmission or distribution line, the licensee may at
his own expense, erect and maintain a gate in that fence.

(2) A licensee who has erected a gate in terms of subparagraph (1) shall provide a
lock for the gate and supply a key for the lock to the owner or occupier of the
land on which the gate is erected.

(3) Any person intending to erect a fence that would render it impossible or
inconvenient for a licensee to obtain access to hi transmission or distribution
line shall give the licensee one month’s notice in writing of his intention to erect
the fence.

Trees obstructing transmission or distribution lines

7. (1) Trees or undergrowth which, in the opinion of a licensee, obstruct or interfere with
or are likely to interfere with the working or maintenance of any transmission or
49
 distribution or distribution line shall on fourteen days’ notice by the licensee and to
such extent as the licensee may consider necessary be cut down or trimmed –
(a) By the authority responsible for the care and management of the land, road or
street concerned, where the trees or undergrowth are growing on state land ,
other than state land which has been leased or on Communal Land or on a road
or street.
(b) By the owner or occupier of the land or concerned in any other case.
(2) If the authority, owner or occupier referred to in subparagraph (1) objects to the
exercise of the powers referred to in that subparagraph, he may lodge written
notice of his objection and his reasons therefor with the licensee concerned and
on receipt of such objection, the licensee shall refer to the matter to the
Commission whose decision shall be final:
Provided that an objection shall be lodged within fourteen days of receipt of the
notice given in terms of subparagraph (1).
(3) Before making any decision or order in terms of subparagraph (2), the
Commission shall give to all parties concerned a reasonable opportunity of
making representations, either in person or in writing.
(4) The commission shall uphold an objection made in terms of subparagraph (2) if
it is shown to its satisfaction that the obstruction to or interference or likely
interference with the transmission line in question can be avoided without
cutting down or trimming any trees or undergrowth and without unreasonable
extra cost to the licensee.
(5) The reasonable expenses incurred in cutting down or trimming trees or
undergrowth in terms of subparagraph (1) shall be borne by the licensee
concerned.
(6) Subject to this paragraph, if the authority, owner or occupier referred to in
subparagraph, the licensee may enter upon the land, road or street as the case
may be in question and cut down or trim the trees or undergrowth to the extent
he considers necessary.
(7) Notwithstanding subparagraph (1), if the working of any transmission or
distribution line is actually interfered with or endangered by any trees or
undergrowth, the licensee concerned may remove the interference or danger
without giving the notice required by subparagraph (1).

Laying of transmission or distribution lines under streets, etc.

8. (1) A licensee may construct and maintain a transmission or distribution line under any
street, road or footpath, and may alter or remove any such line:
Provided that before doing so the licensee shall give reasonable notice to the authority or a
person that owns or has the care and management of the street, road or footpath concerned.
(2) In the exercise of the powers conferred by subparagraph (1), the licensee may
break or open up any street, road or footpath and alter the position thereunder of

50
 any pipe, other than a telecommunication line, main sewer, main drain or gas
main and of any electric cable other than an electric main:
Provided that no alteration in the position of any such pipe or cable shall be made except
under the supervision of a person appointed by the person to whom the pipe or cable
belongs or by whom it is used, unless no such person is appointed or the person so
appointed fails to supervise at the time specified in the notice for the commencement of the
work or discontinues supervision during the work.

Powers to be exercised with care and compensation for damage

9. (1) In the exercise of the power conferred by this Schedule, licensee shall –
(a) Cause as little detriment and inconvenience and do as little damage as possible;
and
(b) Pay compensation to any person who suffers loss or deprivation of rights
through the exercise of the powers conferred by this Schedule; and
(c) If so requested by the Commission, commission a report referred to in
paragraph (b) of subparagraph (2) of paragraph 2 before exercising any power
conferred by paragraphs 3 to 8.
(2) Parts V and VIII of the Land Acquisition Act [Chapter 20:10] shall apply, mutatis
mutandis, to the payment of compensation in terms of subparagraph (1):
Provided that any reference in Part VIII of that Act to the date of publication of a
preliminary notice in the Gazette shall be construed as reference to the date of the
exercise by the licensee concerned of the powers referred to in subparagraph (1).
(3) on completion of any work in connection with the construction, maintenance or
repair of a transmission or distribution line in the exercise of the powers
conferred by this schedule, the licensee concerned shall promptly restore the
surface of any street, road, footpath, land or railway affected thereby as nearly
as reasonably possible to the same condition as that in which it was before the
work was commenced.
(4) While any street, road or footpath is opened, broken up or otherwise obstructed
by the exercise of the powers conferred by this schedule, the licensee concerned
shall cause the obstruction to be fences or guarded and during the night
lightened.
Height and depth of transmission or distribution lines
10. (1) Aerial transmission or distribution wires and cables shall be carried over land at
such height from the surface of the ground as may be prescribed.

(2) An underground transmission or distribution line that is not carried in a pipe or

duct shall be placed such distance below the surface of the ground as may be
prescribed.

(3) If the owner or occupier of any land is obstructed in the use of the land because
a transmission or distribution line insufficiently high, the licensee concerned

51
 shall, subject to paragraphs 5 and 7, take such steps as may be necessary for the
removal of the obstruction.

Acquisition of right or interest in communal land

11. Notwithstanding anything to the contrary in this schedule, no right over or interests in
communal land shall be acquired, whether compulsorily or by agreement, otherwise
than in accordance with the Communal Land Act [Chapter 20:04].
Licensee to authorize persons for purposes of Second Schedule
12. The licensee shall furnish every person authorized by him to exercise any of the powers
conferred by this Schedule with a certificate signed by or on behalf of the licensee
stating that the person has been so authorized and such person shall produce such
certificate at the request of any person affected by the exercise of the said powers.

Factories and Works

Act

52
 Chapter 14:08

Revised Edition
1996

Printed by the Government Printer, Harare

FACTORIES AND WORKS ACT

CHAPTER 14:08
FACTORIES AND WORKS ACT

Acts 20/1948. 1/1955 (s.6). 30/1957, 78/1959, 6/1961 (s.12). 31/1965.

23/1968. 8/1976. 22/1976 (s. 87). 42/1976 (s. 31). 31/1983, 8/1988: R.G.Ns. 217/1970. 313/1970.826/1973

ARRANGEMENT OF SECTIONS
PART 1
PRELIMINARY
Section
1. Short title
2. Interpretation
3. Interpretation of “factory”
PART II
ADMINISTRATION
4. Appointment of inspectors
5. Powers
6. Powers of Inspector as to certain defects remediable by local authority
7. Inspector to produce certificate
PART III
REGISTRATION AND CONTROL OF FACTORIES
8. Premises not to be used as factory unless registered
9. Submission of plans for building or alteration of building
10. Registration of factories

53
11. Requirement of inspector
12. Transfer and surrender of certificate of registration

PART IV
MACHINERY AND ACCIDENTS
13. Inspection of machinery by inspectors
14. Accident register and notification of accidents
15. Inquiries by inspectors
PART V
PRECAUTION AGAINST ACCIDENTS TO BUILDING WORKERS
16. Interpretation in Part V
17. Scaffolding
18. Gear used in connection with structural work
19. Powers of inspectors
20. Application of this Part
PART VI
PROCEDURE AND MISCELLANEOUS
21. Acts or omissions by managers, agents or employees
22. Presumptions and proof by affidavit
23. Appeals from decisions of inspectors
24. Appeal from decision of Administrative Court or magistrate
25. Service of notice under this Act
26. Victimization forbidden
27. Provisions of Act cannot be varied by agreement or waived
28. Prohibition of deduction from wages
29. Disclosure of certain information prohibited
30. Offence in connection with safety appliances
31. Offences in relation to inspectors
32. Locking of factories
33. Penalties
34. Regulations
35. Exemption by Minister
36. Application

AN ACT to provide for the registration and control of factories, the regulation of conditions of work in factories,
supervision of the use of machinery, precautions against accident to persons employed on structural work and for
matters incidental to the foregoing.
[Date of commencement: 1st March, 1951.]
[Chapter 14:08]

PART 1 “builder” means a person employed by a

PRELIMINARY builder;
1. Short title “commercial traveler” means an employee
This Act may be cited as the Factories and employed exclusively to travel from a place
Works Act [ Chapter 14:08] to place for the purpose of selling or
obtaining orders for goods, and includes an
2. Interpretation assistant travelling with such employee;
(1) In this Act – “employee” means any person who –
“activity” includes any process, handicraft or (a) Is employed by or works for an employer in or in
occupation; connection with a factory, but does not include a
“area” includes any number of areas whether person employed sole as a commercial traveler,
or not contiguous; caretaker or watchman or in the delivery of goods
“article” includes any solid, liquid or gas, or or messages; or
combination thereof; (b) In any other manner whatsoever assists an
“authority” means the National Social employer in or about a factory in carrying on the
Security Authority established by National business of such factory;
Social Security Authority Act [Chapter “employee” means a person who in connection
17:04]; with a factory employs or provides work for or
permits anyone in any manner whatsoever to assist
54
 him in the carrying on of his business in or about a (ii) The altering, repairing, renovating,
factory; ornamenting, painting, spraying,
“excavation work” includes – polishing, finishing, cleaning, dyeing,
(a) Loosening, taking out and removing – washing or breaking up of any article;
(i) Stone, soil and other material in (iii) The adaption for sale or use of any
connection with the making, repairing, article;
reopening or closing of any trench, (iv) The sorting, assembling or packing,
tunnel or similar excavation; including washing or filling bottles or
(ii) Clay; other containers of any articles;
(iii) Sand from river beds or river banks; (v) The painting, spraying, construction,
(b) Quarrying for stone or gravel; but does not include reconstruction, assembling, repairing or
any excavation work on a mining location or farm breaking up of vehicles or parts thereof;
which is associated with mining or farming (vi) Printing by letterpress, lithography,
operations thereon; photogravure or other similar process
“institution” includes any charitable, educations or including any activity associated with
like institution, whether conducted by the State or the printing industry;
by any other body or person; (vii) The production and storage of gas in a
“local authority” means – holder of more than one hundred and
(a) A municipal council or town council; or fifty cubic metres storage capacity;
(b) A rural district council declared in terms of (viii) The freezing, chilling or storage in cold
subsection (2) to be a local authority for the storage of any article:
purposes of this Act; (ix) The slaughtering of livestock;
“machinery” means – (x) The generation of electricity
(a) Any locomotive or any stationary or portable (xi) Photographic work
engine, boiler or other steam apparatus; and (xii) Any other activity added in terms of
(b) Any appliance or combination or appliances subsection (4); and
intended for developing, receiving, storing,
transmitting or converting power; (b) Any premises on which bookkeeping, typewriting
But does not include a vehicle; or any other electrical work incidental to any
“Minister” means the Minister of Public Service, Labour and activity referred to in paragraph (a) Is performed, if
Social Welfare or any other Minister to whom the President such premises form part of or are connected with
may from time to time assign the administration of this Act; the premises in which the said activity is carried
“occupier”, in relation to a factory, means – on.
(a) The person or persons (other than a manager who
is not also the occupier) in whom is vested the
right to control and manage the activities in such (2) Notwithstanding anything contained in subsection (1)
factory; or “factory” shall not include –
(b) The principal, superintendent or other person in (a) Any premises on which fewer than five persons
charge of an institution in which any factory perform work in any activity referred to in
activity is carried on; subsection (1) unless mechanical power other
“officer” means a person on the fixed establishment of than for ordinary mining purposes, is used in the
the Public Service or an inspector;
activity conducted on such premises, whether
Premises” includes any land structure, vehicle or vessel;
such power is derived from steam, electricity,
“structural work” means any work in connection with
gas, liquid or any other source.
the erection, alteration, renovation, repair or demolition
of any structure, bridge or building and includes any (b) Premises on which any activity referred to in
railway line, road or irrigation, sewerage, excavation or subparagraph (iv) or (viii) of paragraph (a) of
similar work, but does not include any structural work subsection (1) is only incidental to the conduct
on a mining location or farm which is associated with of a business engaged mainly in the sale of
mining or farming operations thereon; goods by wholesale or retail;
(c) Any premises on a mining location in which
(2) with the approval of the Minister to whom he operation associated with such mining location
administration of the Rural District Councils Act are carried on;
[Chapter 29:13] has been assigned, the Minister (d) Private hoses, hotels, boarding-houses in respect
may by notice in a statutory instrument declare a of any activity referred to in subsection (1)
rural district council to be a local authority for the which is ordinary and necessarily incidental to
purposes of this Act. the conduct of such establishments;
(e) Any structural work;
3. Interpretation of “factory” (f) Premises on a farm whereon an individual or
(1) Subject to this section, “factory” means – partnership or group of persons work in any
(a) Any premises on which any person performs work activity referred to in paragraph (a) of
in connection with any business, undertaking or subsection (1) solely on a farm occupied by him
institution, whether as an employer or employee,
or solely in connection with his farming
pupil or inmate of an institution or otherwise in any
operations, unless upon the premises an industry
one or more of the following activities –
(i) The making of any article or part of any
business or undertaking which shall not fall
article; within the exemption conferred by this
paragraph;
55
 (g) A workroom in connection with a prescribed matters of which the Minister is satisfied he has
class of institution; made a satisfactory study.
(h) Any premises used for the purpose of housing
vehicles where only minor adjustments are (4) Every inspector shall be furnished with a
carried out; certificate signed by an officer thereto designated by
(i) Any factory for the manufacture of explosives, the Minister stating that he has been appointed an
the owner of which holds a licence in terms of inspector and the certificate shall state any
the Explosives Act [chapter 10:08] to restrictions area period and conditions relating to the
manufacture explosives on the premises appointment.
concerned.
(5) Where the Minister revokes the appointment of
(3) For the purposes of this section, “power” does not an inspector made under subsection (2) he shall cause
include hand or foot power used to operate any the local authority concerned to be notified in writing
mechanical appliance. of such revocation.

(4) The Minister may by regulation, and any activity to 5. Powers of Inspectors
those specified in paragraph (a) of subsection (1). (1) Any inspector may for the purposes of
ascertain whether the provisions of this Act are being
(5) Before the making of regulation under subsection (4) compiled with –
the Minister shall – (a) Without previous notice at any reasonable time
(a) Cause to be published in the Gazette a notice enter any factory or any premises where
setting forth the purport of the proposed structural work is being performed or a lift or
regulation and calling upon all interested elevator is installed and make such examination
persons who have any objections to lodge them and inquiry as he deems necessary;
in writing at a specified address within thirty (b) While he is on the premises or at any other
days of the date of publication thereof; and reasonable time and place fixed by the inspector
(b) Cause to be published in one or more of the registration certificate or provisional
newspapers within seven days after the factory permit section ten or of any book notice,
publication of such notice a statement directing record, list or other document which by this Act
the attention of all interested persons to that is required to be kept or exhibited;
notice. (c) At any reasonable time and at any place require
from any person who has the possession or
(6) For the purposes of any provision of any provision of custody or control of any such book, notice,
this Act, the Minister may in his discretion order that a record, list or other document the production
part of a factory shall be deemed to be a separate factory thereon then and there or at a reasonable time
or that two or more factories which are occupied by the and place fixed by the inspector;
same occupier shall be deemed to be a single. (d) Examine and make extracts from and copied of
such books, records, lists or documents and may
(7) Whenever in the opinion of the Minister the activities require from any person an explanation of any
of a business would ordinarily constitute a factory if entries therein and may seize any such books,
conducted on single premises and such activities have records, lists or documents as in his opinion
been subdivided into section all or some of which are may afford evidence of any offence under this
conducted on premises not constituting a factory, he may Act;
in his discretion order that all or any portion of the said (e) Take or remove for purposes of analysis
premises shall be deemed to be a factory. samples of any material or substance produced,
used handled or stored on the premises:
PART II Provided that the occupier or builder of
ADMINISTRATION representative of the occupier or builder or the
representative of the occupier or builder of such
4 Appointment of Inspectors premises shall be notified of any samples so taken or
(1) Subject to the law relating to the Public Service, moved;
the Minister shall appoint – And take with him on to nay premises an interpreter or
(a) A person to be the Chief Inspector of Factories; other assistant
(b) A person to be an inspector
(2) Any occupier of a factory or builder and every person
(2) The Minister with the approval of a local employed by him shall at all reasonable times furnish such
authority may appoint a person employed by that facilities as are required by the inspector entering the
local authority to be an inspector. premises and for the exercise of his powers under
subsection (1)
(3) The appointment of an inspector may be made for (3) Any inspector may require any employee or building
a specified period or area and the Minister may employee to appear before him at any reasonable time and
annex such condition as he thinks fit to any such place fixed by the inspector and may then and there
appointment and shall restrict an inspector to the question such employee:
exercise of powers and functions in relation to those
56
Provided that the inspector shall, after consultation with (a) A registration certificate issued in respect of
the employer or builder concerned, fix such time and such factory under subsection (2) of section ten;
place so as to inconvenience such employer or builder as or
little as possible. (b) A current provisional factory permit issued in
(4) For the purpose of this section, an interpreter shall respect of such a factory under subsection (3) of
while acting under the lawful direction of the inspector he section ten.
accompanies, be deemed to be an inspector.
(5) Any inspector may question either alone or in the (2) The occupier of a registered factory shall not
presence of any other person, as he thinks fit with respect carry on therein any activity referred to in paragraph
to matters dealt with in this Act, every person whom he (a) of subsection (10 of section three, other than
finds on any premises entered in terms of this section or specified in the registration certificate.
whom he has reasonable grounds for believing to be, or to
have been within the preceding two months, employed on 9. Submission of plans for building or
any premises in respect of which any such provision is alteration of building
applicable.
(6) An inspector shall perform the functions imposed and
(1) Whenever any person intends –
duties conferred upon him by this Act subject to such
(a) To effect any structural or other alterations to
general or special instructions as the Chief Inspector of
any premises registered as a factory under this
Factories may from time to time issue.
Act; or premises registered as a factory under
this Act; or
6. Powers of inspector as to certain defects (b) To erect or to cause to be erected any building
remediable by local authority for use as a factory; or
(c) To alter or add to any existing building not
(1) Where an inspector finds any act or default in relation registered as a factory under this Act with the
to any drain, sanitary convenience, water supply, lighting, intention of using such building or a portion
ventilation, nuisance or other matter in a factory which is thereof as a factory;
liable to be dealt with by a local authority under which is He shall submit to an inspector, in duplicate, plans in
liable to be dealt with by a local authority under any the prescribed form of the site and of the proposed
enactment relating to public health, he shall be the duty of building alterations or additions, together with the
the local authority to make such inquiry into the subject of prescribed particulars.
the notice and take such action thereon as seems to the
local authority proper for the purpose of enforcing the (2) The inspector shall advise the person submitting
enactment and to inform the inspector of the proceedings such plans and particulars whether he considers that
taken in consequence of the notice. –
(2) When an inspector finds any such act or default as (a) The proposed structural or other alteration
aforesaid he may take with him into the factory a medical to any premises registered as a factory
officer of health, health or sanitary inspector or other under this Act would or would not result in
officer of the local authority. such factory being unsuitable in terms of
(3) if, within one month after notice of an act or default is the regulations for use as a factory in
given by an inspector under this section to a local respect of the activity which is specified in
authority, proceedings are not taken for punishing or the registration certificate for such factory;
remedying the act or default the inspector may take the or
like proceedings for the punishment or remedying thereof (b) The proposed building or additions or the
as the local authority might have taken and shall be building altered in the manner proposed
entitled to recover from the local authority as a civil debt would or would not be suitable in terms of
all such expenses incurred in or about any unsuccessful the regulations for use as a factory of the
legal proceedings. nature proposed:
Provided that whenever in terms of any
enactment such plans require the approval of a
local authority or an officer plans require the
7. Inspector to produce approval of a local authority or an officer of a
Any inspector exercising any power or performing any local authority, the inspector shall consult such
duty conferred or imposed upon him by this Act shall, om local authority or office before expressing his
demand, produce the certificate furnished to him in terms opinion.
of subsection (4) of section four.
(3) If the inspector considers that –
PART III (a) The proposed structural or other
REGISTRATION AND CONTROL OF FACTORIES alterations to any premises registered
8. Premises not to be used as factory unless as a factory under this Act would
registered premises registered as a factory being
unsuitable in terms of the regulations
(1) No person occupy or use a factory unless he is the for use as a factory in respect of the
holder – activity which is specified in the

57
 registration certificate for such operations to be carried on the
factory; or premises; or
(b) The proposed building or additions or (c) Register a portion of the premises in the manner
the building altered in the manner prescribed in paragraph (a) and on the ground of
proposed would not be suitable in prescribed unsuitability, refuse to register the
terms of the regulations for as a remaining portion.
factory of the nature proposed;
He shall give the person submitting such (3) Whenever an inspector has refused to register the
plans and particulars the reasons for his whole or any portion of the premises in respect of
opinion. which application has been made, he may issue a
provisional factory permit in the prescribed form in
(4) Where application is made to any local authority or respect of the whole or any specified portion of the
officer of any local authority for the approval, in terms of premises which he has refused to register to be valid
any enactment of any plans for the erection, rebuilding or for a period to be stated in the permit and subject to
alteration of any building used for intended to be used for such conditions as the inspector may specify.
a factory, such local authority or officer as the case may
be, shall submit such plans to an inspector for examination (4) An inspector may in terms of the regulations at
by him, and shall not approve such plans unless the any time by notice in writing to the occupier of a
inspector has notified the local authority or officer, as the factory vary any period, prescribed particulars or
case may be in writing considers the building will be conditions specified in a registration certificate or
suitable for use as a factory of the nature proposed. provisional factory permit.

10. Registration of factories (5) after the registration of any premises as a factory
under this Act, no person shall effect or cause to be
(1) Application for the registration of any effected any structural or other alterations to such
premises as a factory under this Act shall be made to an premises without the written prior approval of an
inspector in the prescribed form by or on behalf of the inspector. If any such alteration is commenced
person occupying or intending to occupy such premises as without such approval, any inspector may by notice
a factory. The applicant shall furnish the prescribed in writing to the occupier, cancel the registration
particulars and plans, together with any additional certificate, whereupon the premises shall cease to be
information or drawings which may be required by the registered as a factory under this Act.
inspector:
Provided that no such additional information or drawings (6) If the occupier of a factory loses the registration
need be supplied by the applicant unless they are required certificate issued to him under subsection (2) or the
of him by the inspector within two weeks of the receipt of provisional factory permit issued to him under
the application by the inspector. subsection (3) or a duplicate registration certificate or
(2) as soon as practicable after receipt of an application duplicate provisional factory permit issued to him
and of any additional information or drawings required in under this subsection, he shall not later than fourteen
terms of subsection (1) and after consultation with the days after the discovery of such loss, obtain a
local authority concerned if any the inspector shall – duplicate registration certificate or duplicate
(a) Register the premises in respect of which the provisional factory permit, as the case may be from
application is made by issuing a registration an inspector upon payment of the prescribed fee.
certificate in the prescribed form, specifying the
activity in respect of which the factory is (7) The occupier of a factory shall exhibit the
registered, the name of the occupier and any registration certificate or provisional factory permit
other prescribed particulars; or issued to him in terms of this section in a glazed
(b) Refuse to register the premises on all or any of frame on the factory premises.
the following grounds –
(i) That the premises are unsuitable in 11 Requirements of Inspector
terms of the regulations for use as a
factory; (1) If, in the opinion of an inspector, an occupier of a
(ii) That, subject to subsection (2) of factory has failed to comply with the regulations
section 24 of the Regional, Tow and applicable to him, or the whole or a part of premises
Country Planning Act [Chapter constituting a registered factory is no longer suitable
29:12], the activity to be carried on in in terms of the regulations for use as a factory, he
the factory or the siting of the factory may–
would be in contravention of any (a) By notice in writing setting forth in what respect
approved scheme, operative regional the occupier has, in his opinion, failed to
plan, operative master plan or comply with such regulations or in what respect
operative local plan as defined in that the premises are in his opinion, no longer
Act; suitable for use as a factory require such
(iii) That the applicant has not obtained occupier to take the steps and make the
any licence or permit required under structural alterations mentioned in such notice;
any other enactment in respect of the or
58
(b) By a similar notice require such occupier to months after his appointment and for any additional
submit to him a statement setting forth the steps period authorized in writing by an inspector.
which such occupier proposes to take and if
structural alterations are proposed, also the
prescribed plans, showing the structural
alterations which such occupier proposes to PART IV
make in order to comply with such regulations MACHINERY AND ACCIDENTS
or to render the premises suitable for use as a
factory; and 13. Inspection of machinery and Inspectors
(c) By further notice in writing require such All boilers and machinery shall be subject to
occupier to take the steps and make the examination and inspection by an inspector
structural alterations so proposed without appointed by the Minister for the purposes of this
modification or with such modification as the Part, and for this purpose an inspector may at any
inspector may determine; reasonable time enter upon any factory or premises
Within a period specified in such notice not being where boilers or machinery are in use.
less than fourteen days.
14 Accident register and notification of
(2) The period within which the requirements of any accidents
notice under subsection (1) are to be compiled with (1) Every occupier of any factory and every
may, at the request of the occupier concerned from builder shall keep in the form and manner prescribed
time to time be extended by an inspector. an accident register and shall record in such register
(3) If the occupier upon whom an inspector has, in the particulars of any accident which he is required to
terms of this section, served notice fails within the notify in terms of subsection (3).
time specified to comply with the requirements (2) Every occupier of any factory and every
contained in such notice, the inspector may by builder shall retained any register kept in terms of
further notice in writing to such occupier cancel the this section for a period of three years subsequent to
registration certificate in respect of such factory the last date upon which an entry was made therein
whereupon the premises shall cease to be registered and shall, on demand by an inspector made therein
as a factory under this Act. and shall on demand by an inspector made at any
(4) If, in the opinion of an inspector, the whole or reasonable time during the said period of three years,
part of any premises constituting a registered factory produce such registered for inspection.
re no longer suitable in terms of the regulations for (3) Whenever any accident occurs in a factory
use as a factory and cannot be rendered suitable, he or on premises where structural work is being
may notice in writing to the occupier cancel the performed or ii connection with machinery and such
registration certificate in respect of that factory, as accident causes loss of human life or injury to an
from a date at least six months after the date of such employee or building employee which results in his
notice and the premises shall thereafter cease to be absence form work for a period of three days or more
registered as a factory under this Act. An inspector or injury to any person not employed on the
may vary or withdraw any such notice. premises, the occupier of the factory or the builder or
user of the machinery as the case may be, shall, as
12 Transfer and surrender of certificate of soon as possible thereafter in the manner and in the
registration form prescribed, notify and inspector in writing of
the accident and of the prescribed particulars.
(1) A registration certificate issued under (4) On or before the tenth day of each month the
subsection (2) of section ten may, with the Chief Inspector of Factories shall report to the
approval of an inspector, be transferred by the Authority all accidents which have been notified in
occupier of the factory concerned to another terms of subsection (3) during the previous month.
person intending to be the occupier. (5) Every medical practitioner who attends any
patient whom he believes to be suffering from lead,
(2) If the occupier of a registered factory ceases phosphorous, arsenical or mercurial poisoning or
to use the premises as a factory, the premises anthrax which may have been contrived as the result
shall unless the registration certificate has in of his employment in a factory shall forthwith report
terms of subsection (1) been transferred to the matter in writing to an inspector.
another occupier, forthwith cease to be a (6) For the purposes of subsection (3) –
registered factory and the occupier shall, within “user of machinery” means the owner of the person
seven days of his ceasing to use the premises as benefiting from the use of the machinery and
a factory, notify an inspector in writing thereof includes the person charged with the supervisor of
and return the registration certificate to him: the machinery.
provided that, in the event of the death or insolvency
of any person or the liquidation or winding-up of any 15 Inquiries by inspectors
company which is an occupier of a factory, his or its (1) Whenever in or about a factory or in
trustee, liquidator or executor may continue to connection with the activities of a factory, r in
occupy such factory for a period not exceeding three connection with structural work or machinery –

59
 (a) Any person is killed or injured as a result of an (4) No builder shall require or permit a crane to be
accident; or installed on scaffolding until he has caused tests to be
(b) Any other occurrence takes place which, in the made by a competent and responsible person to ensure the
opinion of an inspector, might have led to any strength and stability of the said scaffolding.
person being killed or injured; (5) Every builder shall cause all scaffolding in
An inspector may, if he deems it expedient, hold an connection with structural work undertaken by him to be
inquiry into such accident or occurrence. inspected by a competent and responsible person
(2) Any evidence given at such inquiry shall be whenever any additions or alterations to such scaffolding
taken down in writing and shall be transmitted by the have been made.
inspector with his report to the Minister.
(3) In the case of an accident causing loss of life 18 Gear used in connection with structural
or serious bodily injury or where the inquiry reveals work
a contravention of any of the provisions of this Act,
the inspector shall send a copy of his report and of (1) No builder shall require or permit a building
the evidence to the Attorney-General. employee employed on structural work to use in
(4) This section shall not affect any other law connection therewith any gear which is not of adequate
relating to inquests or inquiries into the cause of strength, free from patent defect and in good working
death from other than natural causes. order.
(2) No building employee employed on
PART V structural work shall use in connection therewith any gear
PRECAUTIONS AGAINST ACCIDENTS TO which is not of adequate strength, free from patent defect
BUILDING WORKERS and in good working order.
(3) Every builder shall cause all hoisting
16. Interpretation in Part V machines and tackle to be examined and adequately tested
In this Part and in section thirty-four – before being put into use and every chain, ring, hook,
“competent and responsible person” and “competent shackle, swivel, pulley block, lewis, claw and dog used in
workman”, subject to paragraph (c) of subjection (1) of connection therewith to be periodically examined by a
section nineteen, mean a person or workman, as the case competent and responsible person.
may be, possessing the prescribed qualifications;
“crane” means any engine, hoist, lift or derrick or
19 Powers of inspectors
apparatus or contrivance of a like kind operated by hand
(1) An inspector may by notice in writing to the
or other power used in connection with structural work for
builder concerned order –
hoisting, lowering, carrying or removing from place to
(a) That no scaffolding, crane or gear may be used
place materials or goods, and includes any machinery by
until the inspector has satisfied himself that it
which the crane is operated;
has been tested and complies with the
“gear” includes any ladder, plank, putlog, rope, fastening,
regulations;
host, block, pulley hanger, sling, brace, bracket, chain,
(b) That no excavation work may be proceeded
shore, strut or prop used or intended to be used in
with until the inspector is satisfied that the
connection with scaffolding, the timbering of excavations
timbering complies with the regulations and that
or any appliance used or intended to be used instead of
the regulations have been complied with;
scaffolding;
(c) That any named person shall not be regarded as
“scaffolding” means any structure or framework used for
a competent and responsible person or a
the support or protection of building employees engaged
competent work man for the purposes of
on any structural work and includes a swinging stage.
sections seventeen and eighteen.
(2) An inspector may cancel or amend any notice
17 Scaffolding under subsection (1).

(1) No builder shall require or permit a building 20 Application of this Part

employee to perform structural work which cannot be (1) This part shall only apply in areas prescribed
performed in safety except on scaffolding unless he under subsection (2).
provides scaffolding erected in terms of the regulations. (2) The Minister may, by order in a statutory
instrument prescribe the whole of Zimbabwe or any
(2) No building employee shall perform part or parts thereof to be an area in which this Part
structural work except on scaffolding erected in terms of shall apply.
the regulations if such work cannot be performed in safety
otherwise that on scaffolding. PART VI
(3) No builder shall require or permit any PROCEDURE AND MISCELLANEOUS
scaffolding to be constructed, taken down or substantially
altered except – 21 Acts or omissions by managers, agents or
(a) Under the supervision of a competent and employees
responsible person; and
(b) As far as possible by competent workmen (1) Whenever any manager, agent, architect,
possessing adequate experience in the contractor, employee or building employee of any
construction or removal of scaffolding.
60
 occupier of a factory, employer or builder does or or by his manager, agent or employee or found upon the
omits to do any act which it would be an offence premises concerned shall be admissible in evidence
under this Act for the occupier, employer or builder against him as an admission of the facts set forth in that
to do or omit to do, then, unless it is proved that – statement or entry, unless it is proved that the statement or
(a) Such act or omission occurred without the entry was not made by that occupier, employer or builder
connivance or permission of the occupier of the or by any manager, agent, or employee of that occupier,
occupier, employer or builder; and employer or builder in the course of his work as manager
(b) All reasonable steps were taken by the occupier, or in the course of his agency or employment.
employer or builder to prevent any act or (5) Whenever in any proceedings under this Act
omission of the kind in question; and it is proved that any untrue statement or entry is contained
(c) It was not in any circumstances within the scope in any record kept by any person, he shall be presumed,
or authority in the course of the employment of until the contrary is proved, willfully to have falsified that
the manager, agent, architect, contractor, record.
employee or building or building employee to (6) In any proceedings under this Act, an
do or to omit to do acts, whether lawful or affidavit purporting to be made by an inspector in which it
unlawful, of the character of the act or omission is stated –
charged; (a) That any person is or is not the holder of a
the occupier, employer or builder shall be presumed registration certificate or provisional factory
to have done or omitted to do that act and be liable to permit issued in respect of any premises under
be convicted and sentenced in respect thereof; and subsection (2) or (3) of section ten; or
the fact that he issued instructions forbidding any act (b) That any person is or was the occupier of a
or omission of that kind in question shall not, of factory; or
itself, be accepted as conclusive proof that he took all (c) That any exemption or authorization to depart
reasonable steps to prevent the act or omission. from any provision of this Act has or has not
(2) Whenever any manager, agent, architect, been granted to any person in accordance with
contractor, employee or building employee of any this Act, or has been withdrawn; or
occupier of a factory, employer or builder does or (d) That an inspector has made an order under
omits to do any act which it would be an offence for section nineteen;
the occupier, employer or builder to do or omit to do, (e) Shall on its mere production in those
he shall be liable to be convicted and sentenced in proceedings by any person, be admissible as
respect thereof as if he were the occupier, employer evidence of the facts stated therein,
or builder. provided that the officer presiding over the
(3) Any such manager, agent, agent, architect, proceedings at which any such affidavit is adduced in
contractor, employee or building employee may be evidence may cause the inspector to be summoned to
so convicted and sentenced in addition to the give oral evidence in the proceedings in question or
occupier, employer or builder. may cause written, interrogatories and any reply on
oath thereto purporting to be a reply from the
22. Presumption and proof by affidavit inspector shall in like manner be admissible as
evidence in such proceedings.
(1) proof of publication in the Gazette of
regulations in terms of subsection (4) of section three (7) A certificate signed by the registrar of the
shall be conclusive matters precedent and incidental Administrative Court or magistrate, as the case may be,
to the publication thereof, have been complied with. setting out the terms of any decision given on appeal in
(2) Whenever in any proceedings under this Act terms of section twenty –three shall, on its mere
it is proved that any person was present on any production by any person be conclusive proof of such
premises used as a factory that person shall, until the decision.
contrary is proved be presumed to be an employee.
(3) In the absence of satisfactory proof of age, 23 Appeals from decisions of inspectors
the age of any person shall, in any proceedings under
this Act, be presumed to be that stated by an (1) Any person who considers himself aggrieved
inspector to be in his opinion the probable age of that by a requirement or other decision of an inspector under
person, but any interested person who is dissatisfied subsection (2) or (4) of section nine, subsection (2), (3),
with that statement of opinion may, at his own (4), or (5) of section ten, subsection (1), (2), (3) or (4) of
expense, cause the person whose age is in question to section eleven, subsection (1) or (2) of section twelve,
appear before and be examined by a medical section nineteen or any regulations may, within fourteen
practitioner who examined in a certificate by the days of the date of such requirement or decision, lodge an
medical practitioner who examined that person as to appeal in the prescribed form and manner.
what in his opinion is the probable age of that person
shall but only for the purpose of the said proceedings, (2) Appeals in respect of a requirement or
be prima facie proof as to the age of that person. decision of an inspector under subsection (1) or (2) of
(4) In any proceedings under this Act, any section twelve, section nineteen or any regulations shall be
statement or entry contained in any book or document made to any magistrate of the province appointed for the
kept by the occupier of a factory, an employer or a builder purpose of this section by the Minister responsible for
justice , the Chief Magistrate or the provincial magistrate
61
of the province in which the factory, premises or structural position to his disadvantage relatively to other
work is situated or, in respect of a requirement or decision persons employed by such employer by reason
under any of the other sections mentioned in subsection of the fact he suspects or believes, whether or
(1), to the Administrative Court. not the suspicion or belief is justified or correct,
(3) The Administrative Court or the magistrate, that that person has given any information
as the case may be, (hereinafter in this section called the which under this Act he could be required to
court) shall confirm the decision of the inspector or give give to an inspector or has complied with any
such other decision as in its opinion the inspector or give lawful requirement of an inspector or has given
such other decision as in its opinion the inspector ought to evidence in any proceedings under this Act.
have given and for the purpose of this Act, the court’s (2) An employer who contravenes subsection (1)
decision shall be deemed to be the decision of the shall be guilty of an offence and the court which
inspector given on the date on which the court gives such convicts him may, in addition to any sentence,
decision. which it may impose –
(4) A decision given by the court in terms of (a) In the case of an employee the
subsection (3) shall, subject to section twenty-four, be reduction of the rate of whose
final. remuneration or the alteration of
whose position was the subject of the
24 Appeal from decision of Administrative charge, order the employer to restore
Court or magistrate the position of such employee to that
existing prior to the reduction or
(1) On the decision by the Administrative Court alteration, with effect from the date on
or a magistrate of any appeal under this Act, any party which the reduction was made or his
who is dissatisfied – position was so altered; and
(a) With the decision as being erroneous in point of (b) In the case of an employee whose
law; or dismissal was the subject of the
(b) With any decision of the president of the charge, order the employer to pay to
Administrative Court as to whether a matter for the said employee a sum estimated by
decision is a matter of fact or a matter of law; the court to be equal to three months’
may appeal to the Supreme Court. remuneration at the rate according to
which he was being remunerated at
(2) Upon the hearing of the appeal the Supreme the time of his dismissal.
Court may – (3) Any order made under subsection (2) shall have
(a) Confirm vary or reverse the decision the effect of and may be executed as if it were a
appealed from; civil judgement in favour of the Minister, and
(b) Remit the matter to the Administrative any moneys recovered shall be paid to the
Court or magistrate as the case may be, employee concerned.
with instructions in regard to the taking of (4) For the purposes of this section, the definitions
further evidence or the setting out of of “employed” and “employee” shall not be
further information; confined to persons connected with a factory.
(c) Take any other course which may lead to
the just, speedy and as much as may be 27 Provision of Act cannot be varied by
inexpensive settlement of the appeal; agreement or waived
(d) Make such order as to costs as it may deem
just No agreement, express or implied, shall operate to permit
Supreme Court shall be deemed to be the of the application to any employee of any treatment or the
decision of the inspector given on the date on grant to him of any benefits less favourable to him than
which the Supreme Court gives such decision. the treatment or benefits in this Act prescribed; nor shall it
affect any waiver by any employee of the application to
25 Service of notice under this Act him of any provision of this Act. Any person who enters
A notice under this Act to any person may be into any agreement purporting to permit of any such
served on him personally or by posting a application or grant or to effect any such waiver shall be
registered letter addressed to him personally or guilty of an offence and any such agreement shall be void.
under his usual business name or style at his
place of business or his residence. Any notice to 28 Prohibition of deduction from wages
the occupier of a factory may also be served by (1) Any employer, builder or occupier o f a factory
means of an entry in the factory register. who in respect of anything required to be done
or provided by him in pursuance of this Act
26 Victimization forbidden makes any deduction form or reduces the
remuneration of any employee, or required any
(1) No employer shall dismiss any person employed employee to make a payment in respect of such
by him or reduce the rate of his remuneration or requirement to any other person, shall be guilty
alter the conditions of his employment to of an offence.
conditions less favourable to him or alter his

62
 (2) For the purposes of subsection (1), the definition (d) Delays or hinders an inspector in the exercise of
of “employee” shall not be confined to persons his functions; or
connected with a factory. (e) Falsifies or makes any false entry in any
register, record or return he is required to keep
29 Disclosure of certain information prohibited or make under this Act;
(1) If any person in the exercise of his powers under shall be guilty of an offence.
this Act or in the performance of his duties in
carrying out this Act acquires information 32 Locking of factories
relating to the affairs of any other person, firm No occupier of a factory or employer shall,
or business or to any manufacturing or without good reason cause or permit all the entrances to
commercial secrets or working processes, he his factory at the same time to be locked or otherwise
shall not, save for the purposes of legal rendered incapable of being opened from the outside
proceedings under this Act disclose such while any work is being performed in such factory.
information to any other person, except –
(a) To a court of law or to any person 33 Penalties
who by law is invested with the power (1) Any person who is convicted of an offence
to compel the disclosure of such under section twenty-six shall be liable to a fine
information; or not exceeding six hundred dollars or to
(b) To the Minister or to any person imprisonment for a period not exceeding two
acting in the execution of this Act, in years or to both such fine and such
so far as such information may be imprisonment.
necessary for the execution thereof. (2) Any person who contravenes any provision of
(2) Any person who willfully contravenes this Act or any order, notice or requirement
subsection (1) shall be guilty of an offence. under this Act shall be guilty of an offence and
if no special penalty is prescribed therefor, shall
30 Offences in connection with safety appliances be liable –
(1) No person shall – (a) On a first conviction, to a fine not
(a) Willfully or negligently injure or exceeding one thousand dollars or to
interfere with; or imprisonment for a period not
(b) Misuse or exceeding two years or to both such
(c) In a negligent manner use; fine and such imprisonment;
any means appliance, convenience or other (b) On a second or subsequent conviction
thing provided in pursuance of this Act for to a fine not exceeding two thousand
securing the health, safety or welfare of dollars or to imprisonment for a
employed in any factory or place where period not exceeding four years or to
structural work is being performed. both such fine and such imprisonment.
(2) Where any means, appliance or other think for (3) If any person continues an offence after his
securing health or safety is provided under the prosecution therefor under this Act he shall be
requirements of this Act for the use of an liable to further prosecution or prosecutions for
employee engaged in any process he shall use such offence.
such means, appliance or other thing while so
engaged. 34 Regulations
(3) No employee shall, willfully and without (1) The Minister may make regulations as to –
reasonable cause or negligently, do anything (a) (i) The construction, layout and
likely to endanger the health, safety or welfare equipment of factories;
of himself or others. (ii) The character, site, structure,
(4) Any person who contravenes any of the lighting, ventilation, cleansing,
provision of this section shall be guilty of an drainage and water supply of any
offence. factory;
(5) For the purposes of this section, the definition of (iii) the machinery, apparatus,
“employee” shall not be confined to persons appliances, instruments and utensils to
connection with a factory. be used in a factory;
(b) The measures to be taken to secure
31 Offences in relation to inspectors cleanliness, safety and preservation of
Any person who – health, including sanitation ventilation
(a) Falsely holds himself out to be an inspector; or and lighting, in or about factories and
(b) Refuses or fails to answer to the best of his on or about premises where structural
power any question which an inspector in the work or excavation work is
exercise of his functions has put to him; or performed, and the duties of occupiers
(c) Refuses or fails to comply to the best of his of factories, builders, employers and
power with any lawful requirement or order employees and building employees in
made by an inspector; or connection therewith;

63
 (c) The accommodation facilities and
conveniences to be provided in
factories by occupiers for employees
while they are working, resting or
eating therein;
(d) The clothing, safety devices and
protective articles and protective
measures to be provided by
employers, builders and occupiers of
factories for employees who handle
specified articles in the course of their
work or who are employed in
specified activities and under
specified conditions;
(e) The first aid equipment to be provided
by occupiers of factories and builders
and the employment of persons who
hold specified qualifications in first
aid;
(f) The steps to be taken by the owners of
buildings used or intended for use as
factories or by occupiers of factories
in connection with the structure of
such buildings or otherwise in order to
prevent or extinguish fires, and to
ensure the safety, in the event of fire,
of persons in such buildings;
(g) The medical examination of persons
where such examination is required
under this Act;
(h) The hours and conditions of work of
female and juvenile employees and
the prohibition of the employment of
any person under a specified in any

ZIMBABWE ELECTRICITY SUPPLY

AUTHORITY

64
 ELECTRICAL SAFETY RULES

SECOND EDITION, 1998

ZIMBABWE ELECTRICITY SUPPLY

AUTHORITY

65
 LELECTRICAL SAFETY RULES

SEECOND EDITION, 1998

FOR THE CONTROL, OPERATION AND MAINTANANCE OF

THE AUTHORITY’S GENERATION, TRANSMISSION AND
DISTRIBUTION SYSTEMS.

A - GENERAL

B - OPERATING RULES

C - SAFETY RULES

ISSUED TO:

FULL NAME : ………………………………......

SIGNATURE : …………………………………..

DATE : ………………………………….

FOREWORD

Consistent with the mission of the Authority these Electrical Safety Rules are
intended to promote and ensure a safe, reliable and secure electricity supply

66
environment for the Authority, its stakeholders, employees and members of the
public.

The wide distribution of these rules and intensive training and induction of all
concerned Authority management and staff on the provisions hereof should
greatly contribute to the realisation of our strategic goals and objectives.

67
 ZIMBABWE ELECTRICITY SUPPLY
AUTHORITY

ELECTRICAL SAFETY RULES

CONTENTS PAGE
INTRODUCTION 7
REVISIONS 9

A GENERAL
1.0 Electricity Act…………………………………………………... 10
2.0 Live Line Safety Rules (Supplement)…………………………...10
3.0 Definitions …………………………………………. 11
4.0 Admission to Generating, Switching, stations or Substations 17
5.0 Dangerous Occurrences and Accidents………………………….17
6.0 Duties of Employees and Others………………………………...17
7.0 Issue of Rules……………………………………………………18
8.0 Variation…………………………………………………………18
B OPERATING RULES
9.0 Switching ………………………………………………………..19
10.0 Earthing…………………………………………………………..22
11.0 Loading Instructions to Generating Stations……………………..23
12.0 Telephone and Radio Messages……………………..…………...24
13.0 Failure of Supply………………………………………………....25
C SAFETY RULES
14.0 General Safety Rules……………………………………………..26
15.0 Access to High Voltage Enclosures……………………………...29
16.0 Earthing………………………………………………………..…31
17.0 Permits-to-Work and Sanctions-for-Test………………………...32
18.0 Limitation-of-Access……………………………………………..39
19.0 Work in Substations and Switching Stations
Containing Exposed Live Conductors……………………………42
20.0 Work on Remotely or Automatically Controlled
Plant or Equipment……………………………………………….44
21.0 Work on High Voltage Plant or Equipment other than
68
 Metal-Clad Switchgear Spouts and Overhead lines………………44
22.0 Work on Metal-Clad Switchgear, Busbar, Feeder
And Transformer Spouts………………………………………….47
23.0 Work on High Voltage Windings of Generators and
Directly connected Unit Transformers……………………………48
24.0 Work on High Voltage Cables and Overhead Lines……………...49
25.0 Testing of High Voltage Plant or Equipment……………………..54
26.0 Work on High Voltage Plant or Equipment operated by
Or containing compressed air……………………………………..55
27.0 Work on High Voltage Plant or Equipment and Ancillary
Plant or Equipment containing Sulphur Hexaflouride (SF6) gas….57
28.0 Work in Oil Tanks………………………………………………...58
29.0 Fire Protection Equipment………………………………………..59
30.0 Treatment of Electric Shock……………………………………...60
Appendix i. Treatment of electric Shock………………………...61
ii. Permit-to-Work……………………………………..68
iii. Sanction-for-Test…………………………………...76
iv. Limitation –of – Access…………………………….83
v. Visitor’s Live Enclosure Permit………………….....88
vi. Minimum Heights of Overhead Lines at
Road and Railway Crossing Points………………….89

69
 ZIMBABWE ELECTRICITY SUPPLY
AUTHORITY

ELECTRICAL SAFETY RULES

FOR THE CONTROL, OPERATION AND MAINTENANCE OF THE

AUTHORITY’S GENERATION, TRANSMISSION AND DISTRIBUTION
SYSTEMS.

INTRODUCTION:

Significant power system developments which have occurred since the

publication of the First Edition of the Zimbabwe Electricity Supply Authority
Electrical Safety Rules, 1988 and the invaluable operational experience gained
from the application of the 1988 Rules, have necessitated a thorough revision of
these Rules and, thus the compilation of this updated Second Edition of the
Electrical Safety Rules which supersedes the First Edition, 1988.

These Rules are designed and intended for the protection of the Authority’s staff
and other persons against loss of life or limb and injury or damage to person or
property, the prevention of loss, damage or destruction of Authority property and
to ensure a safe and secure environment for the efficient control, operation and
maintenance of the Authority’s plant and equipment. To this end, these Rules
shall be strictly followed and observed and no person shall be permitted or
required to control, operate or maintain any of the Authority’s Generation,
Transmission or Distribution plant or equipment unless he/she satisfies the
Authority duly authorized official as to his/her adequate knowledge and
understanding of these Rules and System Operation procedures in so far as they
relate or apply to the particular job which he/she intends to do.

Any employee who may be in doubt as to the interpretation or application of

these Rules should refer the same to his/her immediate supervisor or appropriate
70
local senior official for advice and guidance. In this regard in addition to ensuring
that employees observe and abide by these Rules, all supervisors and local senior
officials are required to ensure that their subordinates understand and
appreciate the significance of these Rules by, amongst other things, regularly
carrying out practical appraisals and assessments of the situation within their
areas of jurisdiction.

These Rules may at any time, be reviewed and revised by the Chief Executive or
his authorized representative, in which event all employees issued with the Rules
or engaged in the control, operation or maintenance of the Authority’s plant or
equipment shall be advised in writing or such revisions

ENGINEER S.E. MANGWENGWENDE

Chief Executive

REVISIONS

71
Each revision to the Electrical Safety Rules will be numbered and this table is
provided so that you can record the revisions as they are received and fixed in
your copy of the Rules. This will enable you to keep your copy up to date.

Revision No Rule No. Page No. Received Date

72
 ZIMBABWE ELECTRICITY SUPPLY
AUTHORITY

ELECTRICAL SAFETY RULES

SECOND EDITION, 1998

THE CONTROL OPERATION AND MAINTENANCE THE
AUTHORITY’S GENERATION, TRANSMISSION DISTRIBUTION
SYSTEMS

A. GENERAL
Electricity Act - The authority is required to comply with the provision
of the Electricity of the Electricity Act 1985, and with any Regulation made
thereunder, all agents and employees of the Authority are required to conduct
their work in accordance with the Act and Regulations. A copy of the Act and
Regulations shall be kept available for reference in all relevant premises occupied
by the Authority.

Live Line Safety Rules (Supplement) – These rules are issued as a supplement
to the Electrical Safety Rules and must be read and understood as such.
Employees performing live line work or required to issue live line permits-to-
work must be fully aware of and conversant with both the Electrical Safety Rules
and the Live Safety Rules (Supplement).

73
3.0 Definitions

3.1 Approved – sanctioned by the Chief Executive or his Authorized

Representative

3.2 Authorized Representative – The Chief Executives appointee.

3.3 Categories of Authorized Persons:

3.3.1 Competent Person – person over 18 years of age who has sufficient
technical knowledge and experience to safely carry out specific tasks /
functions.
3.3.2 Junior Authorized Person – a Competent Person appointed in writing
by the Authority to carry out specific work on the Authority’s Power
System in accordance with his/her Certificate of Authorization. A Junior
Authorized Person shall not issue or cancel Permit-to-work or Live Line
Permit-to-Work or Sanction-for-Test or Limitation-of-Access
documents.

This category includes those involved in Direct Wire Board (DWB) and
Supervisory Control and Data Acquisition (SCADA) operations such as
may be found in Power Stations, Substations and Control Centres.

3.3.3 Senior Authorized Person – a Competent Person appointed in writing

by the Authority to carry out work and all forms of switching on the
Authority’s Power System in accordance with his/her Certificate of
Authorization.

His/her functions include those of a Junior Authorized Person.

A Senior Authorized Person is permitted to issue and cancel Permit-to-

Work, Live Lie Permit-to-Work, Sanction-for-Test and Limitation-of-
Access documents.

3.4 Certificate of Authorization – a certification given to a Competent

Person by the Chief Executive or his Authorized Representative
confirming that he/she has proved himself/ herself capable of carrying out
the duties he/she is expected to perform and defining the limits of his/her
authorization.

74
3.5 Contractor’s Representative – a Competent Person, other than a person
employed by the Authority, who is required to work on the Authority’s
plant and equipment.

3.6 Controller - a Senior Authorized Person appointed in writing by the

Authority to control power in one or more of the specific fields of
Generation, Transmission, Subtransmission or Distribution and whose
duties are to maintain maximum safety at all times to personnel and plant
and equipment on the Authority’s Power System. The Controller shall
approve all operation on the Authority’s plant and equipment and shall
consent to all issues and cancellations of Permit-to-Work, Live Line
Permit-to-Work and Sanction-for-Test documents.

3.7 Danger - a risk of loss of life, bodily injury or damage to health from
shock, burn or other cause arising from the generation, transmission,
distribution or use of electrical energy.

3.8 Dead - at, or at about zero potential with respect to earth and disconnected
from any live system.

3.9 Earthing:

3.9.1 Additional Earth - any earth connection which is applied after the issue
of a Permit-to-Work or Sanction-for-Test.

3.9.2 Circuit Main Earth - any earth connection which is applied on the
instructions of a Controller before the issue of a Permit-to Work or
Sanction-for-Test.
3.9.3 Earthed - effectively connected to the general mass of earth in such a
way as to ensure at all times an immediate discharge of electrical energy
without danger.
3.10 Live - electrically charged
3.11 Live Enclosure - any area within Generating stations, switching staions
or substations in which live conductors operating at medium voltage or
above exist.
3.12 Live Line Equipment - any approved appliance for use when working
on live plant and equipment.

3.13 Notices:

75
3.13.1Caution Notice - a portable notice in approved from attached to plant or
equipment and/or its control devices, conveying a warning against
interference with the plant or equipment and /or its control devices.
3.13.2Danger Notice - a portable notice in approved from attached to plant or
equipment when live, calling attention to danger of approach to, or
interference with, the plant or equipment.

3.14 Power System - all plant and equipment on the Generation,

Transmission and Distribution networks under the jurisdiction of the
Authority.

3.15 Safety Documents:

3.15.1Limitation-of-Access - a form of declaration signed and given by a

Senior Authorized Person to a Competent Person in charge of work in any
generating station, switching station or substation (where a Permit-to-
Work, Live Line Permit-to-Work or Sanction-for-Test is not applicable
defining the limits of the area within which the work is to be performed.

3.15.2Live Line Permit –to-Work - a form of declaration signed and given by

a Senior Authorized Person to live line linesman in charge of the live line
work to be carried out on the Authority’s plant and equipment exactly what
points of the supply have has placed on them a live Line Caution Notice;
what remote control devices have has a Live Line Caution Notice placed
on them; what auto – reclosing devices including remote control, have
been switched off or disabled and what equipment he is permitted to work
on.

3.15.3Permit-to Work - a form of declaration signed and given by a Senior

Authorised Person to a Competent Person in charge of work to be
carried out on the Authority’s high voltage plant and equipment for the
purpose of making known to that person exactly what plant and equipment
is dead, isolated from all points of supply and feed-back earthed, and on
which it is safe to work.

3.15.4Sanction-for-Test - a form of declaration signed and given by a Senior

Authorised Person to a Senior Authorised Person in charge of testing of
the Authority’s high voltage plant and equipment for the purpose of
making known to such person exactly what plant and equipment is to be
tested and the condition under which testing is to be carried out.

76
3.15.5Visitor’s Live Enclosure Permit - a form signed by visitors
acknowledging their understanding of the danger of entering a live
enclosure and to indemnify the Authority against injury whilst they are in
or about the live enclosure. The form shall also be signed by a Local
Senior Official or Senior Authorised Person.

3.16 Switching:
3.16.1Routine Switching - the operation of tap changers, switchgear
including isolators, and other methods of making or breading circuit.

3.16.2Emergency Switching - opening of circuit breakers, isolators, links, hot

line taps or other devices in order to avoid immediate danger to life or
damage to plant or equipment.

3.17 Working Party - persons working under the immediate supervision of a

Competent Person.

3.18 Worker’s Declaration - a form signed by members of a working party

acknowledging their understanding of the nature of work to be undertaken,
and the area in which it is sage to work.

3.19 Voltage:
3.19.1High Voltage - any voltage in excess of 650 volts.
3.19.2Medium Voltage - any voltage exceeding 250 volts up to and including
650volts.
3.19.3Low Voltage - any voltage up to and including 250 volts.

4.0 Admission to Generating Stations, Switching Stations or Substations

No person shall enter any generating station switching station or substation
wholly occupied by the Authority without the permission of a local senior
official.
5.0 Dangerous Occurrences and Accidents
All dangerous occurrences and accidents on the Authority power system
shall be reported immediately to the Controller who shall immediately pass
on the relevant information to his/her immediate supervisor.

In addition, accidents must be reported in terms of the Electricity Act

Chapter 13:05 and/or the Factories and Works Act Chapter 28:3.
6.0 Duties of Employees and Others
6.1 These Rules are designed to protect the Authority’s employees and others
against danger in the course of their duties and to ensure the efficient and
77
 safe control, operation and maintenance of the Authority’s Generation,
Transmission and Distribution systems.

6.2 These rules must be familiar to all employees who may be concerned with
the Authority’s plant and equipment, and must be strictly observed
Employees of Contractors and others having occasion to operate or work
on the Authority’s plant and equipment are also required to be familiar
with relevant Rules applicable to the work involved, and to observe them.
7.0 Issue of Rules
7.1 A copy of these Rules shall be supplied to all Competent Persons
concerned with the control, operation or maintenance of the Authority’s
plant and equipment and each recipient shall sign a receipt for his/her
copy. This copy shall be kept in good condition.
7.2 The Local Senior Official of each generating station, major substation and
Control Centre shall make available a copy of these Rules at all times for
reference.
8.0. Variation of Rules
In exceptional circumstances these Rules may be varied to the extend
which may be authorized in writing by the Chief Executive or his
Authorised Representative.

B OPERATING RULES

9.0 Switching

Operating of Circuit Breakers and Isolators

(a) No switching or associated operations shall be carried out without the

instruction of the Controller except in cases of immediate danger to
persons or plant or equipment.

(b) When the Controller requires switching to be carried out, he/she shall
communicate directly with the Junior or Senior Authorised Person who
is to carry out the switching. In the absence or failure of direct
communication facilities the message may be relayed by a competent third
party.

(c) Before any switching or associated operation is carried out on the

Authority’s Power System, which many affect other systems, the
78
 Controller shall communicate with the appropriate official(s) of the
system(s) concerned and the routine switching shall be agreed between
them. The high voltage switching shall be recorded at all centres
concerned.

(d) Switching or operations to Controller’s instructions shall be carried out

without undue delay. All switching or operations, whether to the
Controller’s instructions, or when there is immediate danger to life, plant
or equipment, shall be reported to the Controller as soon as possible. The
circumstances of an occurrence necessitating any emergency switching
shall be reported at the time.

(e) Should any plant or equipment show signs of faulty operation, the
circumstances shall be reported to the controller and the plant or
equipment shall be examined before further operation.

(f) When any person receives instructions regarding work on, or the operation
of plant and equipment, he/she shall report any objection to the carrying
out of the instructions to the Controller who shall then have the matter
investigated and, if necessary, referred to higher authority.

(g) Where the Controller is not in direct/indirect communication with a

Senior Authorised Person, the Controller shall hand-over control of a
section of the network under his authority to the Senior Authorised
Person to perform a specific task or operation. Control is to be handed
back to the Controller as soon as practicable. The control hand-over must
be recorded on an approved form.

11.0 Recording of Earthing:

The Controller shall record in his log book or other approved from the
time of application and the location of all Circuit Main Earth connections
and the time of their removal.

11.0 Loading Instructions to Generating Stations

11.1 Load Allocation:

(a) The allocation of load to the Authority’s generating stations and to

generating stations interconnected with the Authority’s transmission
lines and substations in accordance with the Electricity Act, 1985, is
the responsibility of the Controller, and will be varied by him for
79
 time to time as required by system conditions and by the terms of
any agreement entered into between the Authority and the owners of
the said interconnected stations.

(b) The output of other privately or publicly owned generating stations

whose operations the Authority has entered into an agreement will
also be supervised by the Controller to the extent required by the
relevant Agreements.

(c) Any person receiving instructions from the Controller regarding

station loading, voltage adjustment, frequency control and associated
matters shall carry out the instructions without undue delay and shall
report back the completion of the operations to the Controller.

(d) When any person receives instructions regarding load allocation,

he/she shall report any objection to the carrying out of the
instructions to the Controller who shall then have the matte
investigated and, if necessary, referred to higher authority.

11.2 Recording of Loading Instruction:

The Controller shall record in his/her log book or other approved form the
time and nature of all loading and associated instructions issued by
him/her, and may add such explanatory notes as he/she deems to be
necessary or useful.

Any person receiving load allocation instructions shall record in his/her log
book or other approved form the time and nature of all loading and
associated instructions.

12.0 Telephone and Radio Messages

Every telephone or radio message relating to operation of the high voltage

system shall be written down by its sender and receiver, without alteration
or abbreviation (other than those approved), together with a record of the
time of receipt, and shall be read back by the receiver to the sender exactly
as written to ensure that it has been accurately received and understood.

13.0 Failure of Supply

80
 A failure of supply, from whatever cause, to or from any part of the
Authority’s power system shall be immediately reported to the
Controller.

During failures of supply all plant and equipment on the circuit(s) affected
shall be treated as being live.

C. SAFETY RULES

14.0 General Safety Rules

14.1 Work on High Voltage Plant and Equipment

No person shall carry out work (including maintenance, repairs, cleaning

and testing) on any part of high voltage plant and equipment unless this
part of the plant or equipment is:
(a) dead,
(b) isolated and all necessary steps have been taken to lock off from live
plant or equipment;
(c) efficiently connected to earth at all points of disconnection of supply to
the plant or equipment, or between such points and the point(s) of work;
(d) screened where necessary to prevent danger and Caution and Danger
Notices fixed;
(e) released for work by the issue of a Permit-to-Work or Sanction-for-
Test to a person who is fully conversant with the nature and the extent
of the work to be done.

It is the duty of the person issuing the Permit-to-Work of Sanction-for-

Test to satisfy himself/herself that the foregoing provisions are complied
with.

14.2 Interference with Plant and Equipment:

No person shall touch or interfered with the high voltage insulation which
covers or supports any plant or equipment unless the plant or equipment is
dead, isolated and earthed. This rule shall also apply for the purpose of
testing, inspection, or other.

14.3 Fixing of Notices, Barriers and Screens:

81
 (a) Work shall not be carried out on a Permit-to-Work or Sanction-for-Test
on any plant or equipment which has been made dead and earthed until
Caution Notices have been attached to all points where such plant or
equipment can be made live. Danger Notices shall also be attached to or
placed adjacent to the live plant or equipment and at the limits of the zone
marked by screens/barriers in which work may be carried out. Caution
Notices, Danger Notices, barriers and screens shall be fixed and moved
only by or under the supervision of a Senior Authorised Person.

(b) Where necessary, Danger Notices, barriers and screens shall be attached to
or placed adjacent to live plant and equipment and at the limits of the area
in which work may be carried out, before the issue of a Limitation-or-
Access.

14.4 Lock-out Boxes/Bars:

Whenever boxes/bars fitted with locks are provided, they will be suitably
located for the reception of keys which secure switches, barriers, spout
shutters, lock-out equipment and other similar devices provided for the
protection of men working under a Permit-to-Work or Sanction-for-Test.

One lock on each box/bar shall be of the type that can be operated only by
a key held by a Senior Authorised Person. The other locks shall be of a
type operated by non-interchangeable keys.

14.5 Work on High Structures and Overhead Lines:

All persons while at work on poles and high structures shall make proper
use of their safety belts and other safety equipment, wear safety clothing
and shall be in visual range of a second person.

Before any plie is climbed it shall be sounded or tested. No pole badly

impaired by decay or damage shall be climbed until it has been supported
by approved means, and then only climbed by one person.

14.6 Work on Plant and Equipment which can be made Live from more
than one System:

(a) The Authority’s Controller shall communicate and agree with the
official(s) of other system(s) concerned before any switching or earthing is

82
 carried out or a Permit-to-Work or Sanction-for-Test is issued for work
on plant or equipment which can be made live from more than one system.

(b) The conditions of Rule 14.1 shall apply.

(c) The switching, earthing, deposit of lock-out-keys in lock-out boxes/bars

and details of any Permit-to-Work or Sanction-for-Test issued shall be
recorded at all centres concerned.

(d) Where appropriate, copies of the Permit-to-Work or Sanction-for-Test

shall be provided to the official(s) of the other system(s).

15.0 Access to High Voltage Enclosures

15.1 Enclosures containing High Voltage Plant or Equipment, Towers and

Gantries:

Where provided all devices installed for prevention of access to live plant
or equipment shall be kept locked. Keys to such devices shall be kept in
key cabinets, where provided, or otherwise under the direct control of the
relevant Controller or Local Senior Official. No person, unless authorized,
may have access to a live enclosure except that that person and those
under his/her supervision be in possession of a Permit-to-Work,
Sanction-for-Test, Limitation-of-Access or Visitor’s Live Enclosure
Permit

15.2 Underground Chambers and Cable Galleries:

Smoking and exposed flames are strictly prohibited in all underground

chambers and cable galleries except where it is specifically permitted in
writing. Entry to any such chambers and galleries is prohibited unless
adequate precautions have been taken (e.g. use of suitable natural or forced
ventilation) and the consent of a Senior Authorised Person obtained.
Where dangerous fumes are liable to be present these precautions shall
include testing for gas by means of an approved detector.

Where one or more persons are required to remain in an underground

chamber in which dangerous fumes are liable to be present, an extra person
shall be kept on duty outside the chamber and such person shall keep in
touch with the person(s) inside the chamber. If necessary, however, such

83
 person may enter the chamber from time to time, although he/she shall not
remain inside for longer than necessary.

15.3 Access for Visitors

Visitors are not permitted inside any live enclosure unless they are
accompanied, without intermission, by a Local Senior Official or Senior
Authorised Person of the Authority. Visitors will be required to read and
sign the Visitor’s Live Enclosure Permit thereby indemnifying the
Authority against any injury which may result.

16.0 Earthing

16.1 Plant or Equipment for Earthing:

When high voltage plant or equipment is to be discharged and earthed, it

shall be done: -

(a) By the use of earthing switches or special equipment where

provided, or,

(b) Where not provided by other approved means.

When a circuit breaker is used to make the earth connection, then the
tripping feature shall be rendered inoperative, and if practicable the
mechanism shall be locked in the closed position.

Earthing devices shall be of an approved type and of adequate current

carrying capacity. earthing devices shall be examined for defects
periodically and always prior to use by a Senior Authorised Person.

16.2 Procedure for the use of Earthing Devices:

(a) Earthing devices shall be connected to the earth system before being
secured to the phases. The earthing connection shall only be secured
to the phases by means of a link stick or other approved equipment
and care must be taken to ensure that good contact is made.

(b) All phases shall be earthed, even if work is to be carried out on one
phase only.

84
 (c) Earthing devices shall not be applied in any busbar chamber or
compartment in which there is danger of accidental contact of the
devices with any live high voltage equipment.

(d) When removing earthing devices, they shall be disconnected from

the phases first and the earth system last.

16.3 Earthing of Metal-clad Switchgear:

Only approved appliances shall be used for the purpose of earthing metal-
clad switchgear. The insertion of the hand or any tool into contact spouts
for this purpose is forbidden.

17.0 Permits-to-Work and Sanctions-for-Test

17.1 Arrangements for Direct Issue:

(a) Permits-to-Work, Sanction-for-Test and Live Line Permits-to-

Work shall be issued with the consent of the Controller, who shall
retain in his/her custody a record of each Permit-to-Work,
Sanction-for-Test and Live Line Permit-to-Work issued.

(b) Work shall not be carried out by any person on high voltage plant or
equipment until Permit-to-Work, Sanction-for-Test or Live Line
Permit-to-Work has been signed and the copy handed by a Senior
Authorised Person to the person in charge of the work. The person
in charge of the work shall then read its contents to the Senior
Authorised Person issuing the Permit-to-Work, Sanction-for-
Test, or Live Line Permit-to-Work, sign the copy and its original
and retain the copy in his /her possession until he/she has signed the
clearance and returned it to a Senior Authorised Person.

(c) If the plant or equipment is interconnected with a high voltage

metered consumer, or, at Inter-connection Substations or Power
Stations and requires isolation or earthing, a Permit-to-Work or
Sanction-for-Test shall only be issued after the Senior Authorised
Person has obtained the signature of the official responsible for the
plant or equipment or the earthing on Section 2 of the Permit-to-
Work or Sanction-for-Test documents.

85
 (d) The person in charge to whom a Permit-to-Work is issued shall be
a Competent Person and the work shall be carried out under his/her
immediate supervision. In the case of an overhead line with all
conductors dead, immediate supervisions shall be deemed to include
the area between additional earths.

In certain cases, a Contractor’s Representative will be the person

in charge of the work, and in such cases the issue of a Permit-to-
Work to the Contractor’s Representative shall appoint him/her a
Competent Person for the work covered by the Permit-to-Work.

(e) No person in receipt of a Permit-to-Work, Sanction-for-Test or

Live Line Permit-to-Work may leave the work area while work is
in progress.

(f) A Permit-to-Work shall be issued to the Competent Person in

charge of each independent working party.

(g) Only one Sanction-for-Test may be issued on high voltage plant or

equipment at any one time and under no circumstances may a
Permit-to-Work be in force on any high voltage plant or
equipment within the points of isolation specified on a Sanction-
for-Test.

17.2 Arrangements for Indirect Issue:

(a) In the case of work on plant or equipment, where, owing to special

circumstances or to the distances involved the arrangements for
direct issue of a Permit-to-Work or Live Line Perming-to-Work
world result in undue delay, the Permit-to-Work or Live Line
Permit-to-Work may be issued by a Senior Authorised Person
with the consent of the Controller, in accordance with these Rules,
and its contents communicated by him/her to the Competent Person
in charge of the work by radio or telephone.

(b) The Competent Person shall enter the details of the Permit-to-
Work or Live Line Permit-to-Work in a Permit-to-Work book or
other approved document and shall read the contents to the Senior
Authorised Person for confirmation.

Rule 17.1 (a), (c), (d), (e) and (f) shall apply.
86
17.3 Worker’s Declaration:

All members of the working party engaged on work for which a Permit-
to-Work or Live Line Permit-to-Work or Sanction-for-Test has been
issued shall first be shown the plant and equipment on which it is safe to
work by the Permit-to-Work holder, and then sign a Worker’s
Declaration form. Names may be added to or deleted from a Workers
Declaration form without reference to the Controller.

17.4 Precautions during Progress of Work:

(a) The plant or equipment isolated and earthed for work under the
terms of a Permit-to-Work must remain so until the Permit-to-
Work must remain so until the Permit-to-Work has been cleared
and cancelled.

(b) Should work for which a Permit-to-Work or Sanction-for-Test has

been issued be such that the plant or equipment may be put into
commission before its completion, then each time the work is
suspended the Permit-to-Wok or Sanction-for-Test shall be
cancelled.

(c) The Senior Authorised Person in receipt of a Sanction-for-Test

shall be responsible for coordinating isolated and earthed for testing
and for ensuring safety during the test in accordance with Rule 9.3.

17.5 Procedure for Clearance and Cancellation after Direct Issue:

(a) On completion or work (or stoppage by a Senior Authorised

Person) for which a Permit-to-Work has been issued:
(i) All members of the working party engaged on work for which a
Permit-to-Work or Live Line Permit-to-Work or Sanction-
for-Test has been issued shall first sign off a Worker’s
Declaration form.

(ii)The Competent Person in charge of work shall then sign the

clearance on all copies if practicable on his/her return to a Senior
Authorised Person who shall then obtain the consent of the
Controller and cancel the Permit-to-Work.

87
 (b) When applicable, the responsible official of the high voltage
metered consumer, or, the Inter-Connection Substation or Power
Station shall sign Section 6 of the Permit-to-Work or Sanction-for-
Test.

(c) On completion of work (or stoppage by a Senior Authorised

Person) for which Sanction-for-Test has been issued the Senior
Authorised Person shall sign the clearance with the exceptions
noted and shall then obtain consent of the Controller to cancel the
Sanction-for-Test document.

17.6 Procedure for Clearance and Cancellation after Indirect Issue:

On completion of work (or stoppage by a Senior Authorised Person) for

which a Permit-to-Work has been issued, the Competent Person in
charge of the work shall ensure that the additional earths and loose gear are
clear and shall then sign the clearance on his/her Permit-to-Work or other
approved document. He/she shall then communicate with the Senior
Authorised Person holding the Permit-to-Work and read Section 4 to
him/her. The Senior Authorised Person shall inform the Controller of
the cancellation of the Permit-to-Work.

17.7 Loss of Permit-to-Work or Sanction-for-Test Documents:

In the event of loss of a Permit-to-Work or Live Line Permit-to-Work

or Sanction-for-Test held by a person in charge of work the loss shall be
reported immediately to the Controller who will arrange for its
cancellation and replacement.

17.8 Loss of Special Keys issued against Permit-to-Work or Sanction-for-

Test

All work covered by a Permit-to-Work or Sanction-for-Test shall cease

immediately on the loss of any key(s) used to lock off plant or equipment
that could be used to make live the work area covered by the Permit-to-
Work or Sanction-for-Test. The loss of the keys shall immediately be
reported to the Controller who shall immediately cancel such Permit-to-
Work or Sanction-for-Test.

88
 The loss of the keys shall make the necessary arrangements for
replacement of the lock(s) and key(s) and shall then issue a new Permit-to-
Work or Sanction-for-Test before work can resume.

17.9 Disposal of Cancelled Permits-to-Work or Sanctions-for-Test:

Cancelled Permits-to-Work or Live Line Permits-to-Work or
Sanctions-for-Test or other approved documents, and copies thereof, shall
be retained at centres concerned for a period of one year from the date of
cancellation.

18.0 Limitations-of-Access

18.1 Arrangements for Issue:

(a) A Limitation-of-Access will be issued by a Senior Authorised

Person without reference to the Controller. The Controller will be
notified as soon as possible after issue, and will record the issue in
his/her log or approved form.

(b) A Limitation-of-Access will be issued to a Competent Person who

is in charge of work in a high voltage premises, the work being such
as will not require the issue of a Permit-to-Work. The Limitation-
of-Access will be signed by a Senior Authorised Person and the
copy handed to the Competent Person in charge of the work.

The Competent Person in charge of the work will then read its
contents to the Senior Authorised Person issuing the Limitation-
of-Access, sign the copy and its original and retain the copy in
his/her possession until he/she has signed the clearance on all copies
if practicable on his/her return to a Senior Authorised Person.

(c) Work shall be carried out under the immediate supervision of a

Competent Person issued with a Limitation-of-Access. The issue
of a Limitation-of-Access to the Contractor’s Representative
shall appoint him/her a Competent Person for the work covered by
the Limitation-of-Access.

(d) No person in receipt of a Limitation-of-Access may leave the site of

the work while work is in progress.

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 (e) A Limitation-of-Access shall be issued to the Competent Person in
charge of each independent working party.

(f) A Limitation-of-Access shall be issued by a Senior Authorised

Person to a Competent Person in charge of work on medium or
low voltage plant and equipment, dead or alive. Whatever
practicable, however, the plant or equipment shall be made dead and
isolated. When work is to be carried out on live medium or low
voltage plant or equipment the relevant “code of Practice” shall be
followed and the Limitation-of-Access shall be stamped “LIVE”.

18.2 Worker’s Declaration:

All members of a working party engaged on work for which a

Limitation-of-Access has been issued shall first sign a Worker’s
Declaration form. Names may be added or deleted form a Worker’s
Declaration form without reference to the Senior Authorised Person.

18.3 Procedure for Clearance and Cancellation:

On completion of work (or stoppage by a Senior Authorised Person) for

which a Limitation-of-Access has been issued, the Competent Person in
charge of the work shall sign the clearance. He/she shall then immediately
return the copy to the Senor Authorised Person who will cancel the
Limitation-of-Access. The Controller will be informed of the
cancellation and will record the cancellation in his/her log or approved
form.

18.4 Loss of Limitation-of-Access Document:

In the event of the loss of a Limitation-of-Access document held by a
Competent Person in charge of work, the loss will be reported to the
Senior Authorised Person who will arrange for its cancellation and
replacement. The action taken will be reported to the Controller.

18.5 Disposal of Cancelled Limitation-of-Access Documents:

Cancelled Limitation-of-Access and copied thereof, shall be retained at

the centres concerned for a period of one year from the date of
cancellation.

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19.0 Work in Substations and Switching Stations Containing Exposed Live
Conductors

19.1 Safety Clearances to Live Conductors:

(a) When work is to be carried out in a Substation in which there are

exposed high voltage conductors, then, unless the whole plant or
equipment is dead, the section which is to be made dead for work to
be carried out shall be defined as far as possible by the use of
barriers, notice boards or roping arranged so that the minimum
clearance from the nearest exposed live conductor to ground level or
to any platform or access way which may be required to be used
shall be:

RELATED VOLTAGE CLEARANCE

Up to and including 33 kV 2.75 m
66kV 3.00 m
88kV 3.20 m
110kV and 132kV 3.50 m
220kV 4.50 m
330kV AND 400kV 5.50 m

The clearance for any intermediate rated voltage shall be that applicable to
the next higher rated voltage.

(b) If the work is such that these clearances are not sufficient to avoid
danger, other approved means shall be taken to provide the requisite
degree of safety.

19.2 Use of Ladders and Long Objects:

(a) Ladders shall be of an approved type and of no greater length than is
required for the work involved.

(b) Ladders and other long objects shall not be used without the
approval of a Senior Authorised Person. The movement and
erection of such ladders and objects shall be carried out only under
the direct supervision of the Competent Person in charge of the
work and when moved at ground level they shall be carried only in
the horizontal position as near ground as practicable.

91
 (c) All portable ladders within substation or switching stations when not
in use shall be securely locked to a suitable anchorage.

19.3 Movement of Cranes and other Plant or Equipment in a Substation:

The Senior Authorised Person shall be directly responsible for

positioning, erection and any subsequent movements of cranes or other
plant or equipment within the substation. The cranes or other plant or
equipment shall be connected to the substation earthing system as soon as
practicable.

20.0 Work on Remotely or Automatically Controlled Plant or Equipment

20.1 Before work is carried out on remotely or automatically controlled plant or

equipment such as circuit breakers, isolators, tap changing gear, or air
compressors, the automatic or remote control features shall first be
rendered inoperative.

20.2 Before any work is commenced on Protection, Communications, Computer

based systems and any other control and Indication circuits, the consent of
the Controller must be obtained and precautions taken to prevent
accidental operations.

21.0 Work on High Voltage Plant or Equipment other than Metal-Clad

Switchgear Spouts and Overhead Lines

Before any person is allowed to carry out any work, such as repairs or
modifications or cleaning, on any high voltage plant or equipment other
than metal-clad switchgear spouts and overhead lines, the following
operations shall be carried out in strict sequence: -

(a) The plant or equipment shall be isolated from all points of supply,
including voltage and auxiliary transformers and common neutral earthing
equipment from which the plant or equipment may become live.

(b) Circuit breakers, isolators, spout shutters, control handles and safety
devices shall be locked in position by the keys provided for the purpose
which shall be placed in the appropriate lock-out box/bar if provided,
except for those required for use under Rule 9.3.

92
 Caution Notices shall be attached at all points where the plant or
equipment can be made live.

The Senior Authorised Person shall operate the lock reserved for his/her
use and each recipient of a Permit-to-Work or Sanction-for-Test shall
use an additional lock and retain the key in his/her possession until he/she
clears the Permit-to-Work or Sanction-for-Test and returns it with the
key to a Senior Authorised Person.

(c) Danger Notices shall be attached to all live plant or equipment adjacent to
the work area.

(d) The carrying out of the above-mentioned operations shall be reported to

the Controller and further instructions received for carrying out the
following:-
(i) The plant or equipment shall be checked to ensure that it is not live,
where practicable, by means of an approved voltage indicator, the
indicator itself being tested before and after the verification.
(ii)It shall then be earthed at all points of isolation for the supply,
including points of isolation from the common neutral earthing
equipment where applicable, or between such points and the points
of work.
(e) If the work is such that operations (a) to (d) have to be carried out at more
than one station the Senior Authorised Person at each station shall lock
the keys involved in the lock-out box/bar, with a non-interchangeable key,
and retain the key in his/her possession until he/she receives instructions
for the Controller to restore the plant or equipment to service.

(f) A Permit-to-Work or Sanction-for-Test shall then be issued.

(g) The plant or equipment shall be earthed by means of additional earths at

the points of work unless the plant or equipment has been bodily removed
from its normal live position. The application of additional earths is not
required where these earths will coincide with a circuit main earth,
except when this circuit main earth is an earth switch.

(h) Circuit Main Earths may be removed under the terms of a Sanction-for-
Test after which they shall be immediately replaced or noted under the
“exceptions” when clearing the Sanction-for-Test.

93
22.0 Work on Metal-Clad Switchgear, Busbar, Feeder and Transformer
Spouts

When work is carried out on spouts, the following operations shall be

carried out in strict sequence: -

(a) The section of busbars or circuit on which work is to be carried out

shall be made dead and shall be isolated from all points of supply.

(b) The isolating devices and the shutters of live spouts shall be locked.

(c) The carrying out of the above-mentioned operations shall be

reported to the Controller and further instructions received for
carrying out the following:
(i) Where practicable the busbars or circuit shall be checked by
means of an approved voltage indicator to verify that they are
dead, the indicator itself tested before and after the
verification.
(ii)Busbars - these shall be earthed with approved earthing
equipment at a panel other than that at which work is to be
done on the isolated section of the busbars.
(iii) Feeder circuits - these shall be earthed with approved
earthing equipment to the feeder spouts.

For the purpose of earthing metal-clad switchgear approved

appliances only shall be used. The insertion of the hand or any
tool into spouts for this purpose is forbidden.

(d) The operations set out in Rule 21.0 (b), (c), (f) and (h) shall also be
carried out.

23.0 Work on High Voltage Windings of Generators and directly connected

Unit Transformers

Work on the high voltage windings of generators and directly connected

unit transformers shall be carried out as far as practicable in accordance
with the requirements of Rule 21.0 and the following additional
precautions shall be taken: -

(a) The generator shall be at rest or on barring.

94
 (b) Where motor-driven exciters are provided, the switch controlling the
motor shall be opened and locked.

(c) The field circuit switch shall be opened and locked.

(d) The valves or gates controlling the prime mover shall be locked in
the closed position.

(e) Caution Notices shall be attached at the points referred to in (b), (c)
and (d).

24.0 Work on High Voltage Cables and Overhead Lines

24.1 High Voltage Cables:

The provisions of Rule 21.0 (a), (b), (c), (d), (e), (f) and (h) shall apply to
work on high voltage cables and in addition the following precautions
shall be taken: -

(a) When any high voltage cable is to be cut or joint opened, a Senior
Authorised Person shall satisfy himself/herself that the cable has
been made dead, identified and spiked to prove dead with approved
devices before the issue of a Permit-to-Work.

(b) No person, after receiving a Permit-to-Work or Sanction-for-Test,

shall work on, or in any way interfere with, any high voltage cable,
conduit, trough or trench containing a high voltage cable until
personally instructed at the point of work by a Senior Authorised
Person.

24.2 Overhead Lines:

24.2.1Towers with all Conductors Dead:

The provisions of Rule 21.0 shall apply to work on Overhead Lines with
all conductors dead and in addition the following precautions shall be
taken: -

(a) At each station involved the Senior Authorised Person shall

personally check the identity of the circuit at the point of isolation
and report to the Controller. He/she shall also lock the lock-out
box/bar if provided at the station with a non-interchangeable key,
and retain the key in his/her possession until he/she receives
95
 instructions for the Controller to restore the plant or equipment to
service. The Permit-to-Work shall then be issued.

(b) Each person who may have to climb a tower shall be provided with a
wristlet market with the circuit designation of the line on which
work is to be carried out and shall wear it in such a manner that it
will be, at times, readily visible to the wearer.

The person who will be in charge at each tower shall be provided

with a green flag and shall place the green flag in a suitable position
before allowing any person to ascend the tower.

(c) Where practicable, the circuit shall be checked at the point of work
by an approved voltage indicator to verify that it is dead, the
indicator itself being tested before and after verification. The
conductors shall then be earthed with additional earths by the
Competent Person at both sides of the point of work, and in no case
shall the additional earths be more than six spans apart.

24.2.2 Towers Carrying Love Conductors:

Work above the anti-climbing devices on towers carrying live

conductors shall be permitted only under the following conditions: -

(a) The work shall be carried out under the terms of a Limitation-of-
Access.

(b) Before anyone is allowed to start work, the Competent Person in

charge at each tower shall define the area to be worked in by
removable barriers, notice boards, roping or pennants arranged to
prevent any person working on the tower within distances specified
in Rule 19.1 (a). While defining the working area the Competent
Person in charge shall be under observation by another person at
ground level.

(c) No person shall work in such a manner that his/her arms or any tool
extend beyond the limit defined in sub paragraph (b).

(d) Upon completion or cessation of the work the Competent Person in

charge shall inform all members of the Working Party that it is no
longer safe to work on the tower and shall then remove the barriers,
96
 notice boards, roping or pennants defining the working area. While
removing the barriers etc, the Competent Person shall be under
observation by another person at ground level.

24.2.3 Double Circuit Overhead Lines with One Circuit Live:

Where work similar to that covered by Rule 24.2.1 has to be carried

out on double circuit overhead lines with one of the circuits live the
provisions of Rule 24.2.2 shall apply, and the following additional
precautions shall be taken: -

After placing in position a green flag on the dead side of the tower,
and before any other person is allowed access to the tower, the
Competent Person in charge at the point of work shall climb the
tower on the dead side, and shall efficiently connect to earth each
individual conductor on that side. He/she shall then affix red
pennants to the crossarms supporting the live conductors at the
junction of these crossarms with the tower body. The conductors
shall remain earthed throughout the progress of the work and the
earths and pennants shall be removed only after all the members of
the Working Party have descended the tower on completion of the
work. While affixing or removing the earths and red pennants, the
Competent Person in charge shall be under observation by another
at ground level.

24.2.4 Poles Carrying Live Conductors:

Work on poles supporting live conductors shall not be carried out
until the provision of Rule 14.5 are satisfied. No person shall work
on any pole which supports both LV and HV conductors for the
purpose of working on the LV conductors unless: -
(i) The safety clearances specified in Rule 19.1 (a) are satisfied and
he/she is in receipt of a Limitation-of-Access; or
(ii)All conductors supported by the pole are covered by a Permit-to-
Work.

In cases where several HV circuits are supported by the same pole, all
circuits concerned shall be covered by a Permit-to-Work before work
commences on the pole.

24.3 Adverse Weather Conditions:

97
 In the event of approach of a lighting storm all work on overhead lines
shall cease immediately, and the Controller shall be informed.

25.0 Testing of High Voltage Plant or Equipment

(a) (i) Pressure tests, or any A.C. testing at pressures above 15 volts,
shall be carried out under the terms of a Sanction-for-Test. A.C.
testing at pressures below 15 volts shall be carried out under the
terms of a Sanction-for-Test or under the terms of a Permit-to-
Work already in force. In the latter case prior agreement must be
reached between the Controller, the Senior Authorised Person
carrying out the testing and the holder of the Permit-to-Work and
details will be logged at the Control Centre and site of work. The
Senior Authorised Person shall ascertain for the Controller that no
other Permit-to-Work and details will be logged at the control
Centre and site of work. The Senior Authorised Person shall
ascertain for the Controller that no other Permit-to-Work has been
issued on the plant or equipment other than Permit-to-Work under
which the testing is to be carried out. D.C. test equipment shall be
used under the supervision of a Senior Authorised Person under the
terms of a Sanction-for-Test.

(b) All cables shall be discharged before and after the application of test
voltage.

(c) Test leads shall be of an adequate size and be easily visible.

26.0 Work on High Voltage Plant or Equipment operated by or containing

compressed air

26.1 Work other than Maintenance Testing or Operational Testing and

Adjustments:

Work other than maintenance testing or operational testing and

adjustments on high voltage plant or equipment operated by or containing
compressed air, shall be carried out only under the following conditions: -

(a) High voltage plant or equipment, after having been isolated, shall be
earthed by a Senior Authorised Person or a Competent Person
acting under his immediate supervision.

98
 (b) (i) the valves controlling the supply of air to the plant or
equipment shall be closed and the air released from the associated
receivers and pipe work which shall be ********atmosphere.

(ii) The valves shall be locked in position and the keys retained
by the Senior Authorised Person. If this is not practicable,
other approved methods shall be used.

(iii) A Permit-to-Work shall be issued to the Competent Person

in charge of the work.

26.2 Maintenance Testing:

Maintenance testing on high voltage plant or equipment operated by or
containing compressed air shall only be carried out under the terms of a
Sanction-for-Test.

26.3 Operational Testing and Adjustments:

Operational testing and adjustments on plant or equipment operated by or
containing compressed air shall be carried out under the direct supervision
of a Senior Authorised Person under the provisions of Rule 14.1.

27.0 Work on High Voltage Plant or Equipment and Ancillary Plant or

Equipment Containing Sulphur Hexafluoride (SF6) gas

(a) For any plant or equipment containing Sulphur hexafluoride gas the
relevant operating instructions must be available at the point of work
stating the method of dealing with the gas and associated
compounds. The plant or equipment shall bear a label stating that it
contains Sulphur hexafluoride.

(b) The requirements of Rule 26.0 shall apply. In addition, the following
special precautions shall be taken when any work involves access to
any part of the plant or equipment which is, or has been in contact
with the gas or associated compounds: -

(i) The plant or equipment shall be isolated from all sources of

supply of gas, purged in accordance with the relevant
operating instructions and the associated receiver(s) and
pipework left open to the atmosphere.

(ii)Where possible valves shall be locked by special safety locks.

99
 (iii) Caution Notices shall be attached to the valves.
(iv) A Permit-to-Work shall be issued to the Competent
Person in charge of the work, or a Limitation-of-Access
when the plant or equipment has been bodily removed from
the circuit.

(c) Approved protective clothing, respirators, eye shields and safe

handling equipment shall be provided and used where danger may
arise from gas or associated compounds in accordance with the
relevant operating instructions.

28.0 Work in Oil Tanks

(a) No person shall enter a vessel which has been emptied of oil or any
other inflammable substance until a Senior Authorised Person is
satisfied that all dangerous vapours have been expelled.

(b) Smoking and exposed flames are prohibited in the vicinity of open
vessels containing or which have contained oil or any other
inflammable substance until the precautions specified in (c) have
been taken.

(c) Work on such vessels particularly the application heat is forbidden

until all practicable steps have been taken to prevent fire or
explosion either by removal of the inflammable substance and any
fumes or by rendering them non-explosive and non-inflammable.

29.0 Fire Protection Equipment

29.1 Automatic Control:

(a) Before work or inspections are carried out in any enclosure
protected by automatic fir extinguishing equipment the automatic
control shall be rendered inoperative and the equipment left on hand
control and a Caution Notice to that effect shall be attached.

(b) The automatic control shall be restored immediately after the

persons engaged on the work or inspections have withdrawn for the
protected enclosures.

100
 (c) The rendering inoperative of the automatic control and the placing
of Caution Notices shall be noted on any Permit-to-Work or
Limitation-of-Access issued for the work in the protected enclosure.

29.2 General:

(a) Contact with some chemicals used in fire protection equipment may
be dangerous, and un such cases notices to that effect shall be
displayed adjacent to the plant or equipment.

(b) Portable firefighting equipment shall not be used on electrical plant

or equipment unless such plant or equipment has been disconnected
from the supply.

(c) Portable CO2 dry chemicals and other approved electrical fire
extinguishers may be used in the vicinity of live electrical plant or
equipment provided that in the handling of the extinguishers the
safety clearances specified in Rule 19.1 are maintained. After the
discharge of portable CO2 or other approved electrical fire
extinguishers in a confined space, the operator shall leave the space
until the precautions set out in (d) have been taken.

(d) After any fire, or the discharge of CO 2 or other approved electrical

fire extinguishers in an enclosed space, the space shall be thoroughly
ventilated before entry or suitable breathing equipment shall be worn
if entry is necessary before the gases have been cleared.

30.0 Treatment of Electric Shock

All persons who may be concerned with the operations of, and work on,
the Authority’s plant and equipment shall make themselves conversant
with the treatment of electric shock. This information is given in Appendix
I

APPENDIX 1 – TREATMENT OF ELECTRIC SHOCK

Order of Action

1. Make sure it is safe to approach.

2. Switch off current if possible or secure release from contact.
101
 3. Start respiratory resuscitation at once if casualty is not breathing and
sent for medical aid.

1. Make sure it is Safe to Approach

Ensure it is safe to approach the casualty without danger to yourself.

2. Switch Off Current if Possible or Secure Release

from Contact

If the casualty is not clear of the source of the shock break contact by
switching off the current, removing the plug or wrenching the cable
free. If this is not possible, stand on dry insulating material such as
newspaper, wood or a rubber mat and try to push or pull the casualty
clear of the contact using a non-metallic brush or stool. Do not touch
the casualty with bare hands, use rubber gloves, but if nothing else is
available then grip any loose dry clothing (not under the arms) and pull
the casualty away from the source.

Start Respiratory Resuscitation at Once if Casualty is not

Breathing and Send for Medical Aid

Check for signs of breathing

Place your ear above the casualty’s’ mouth and look along the chest and
abdomen for signs of movement.

If the casualty is breathing

Place casualty in the recovery position and call medical aid, Figure i.

Figure i - recovery Position

102
If NOT Breathing
Get someone to call medical aid while you begin respiratory resuscitation. Us one
of the following two methods
3.1 Mouth to Mouth Ventilation – Speed is Essential
(i) Check airway is not blocked. Turn head to one side and remove
obstruction around the face and neck and any debris in mouth.
(ii)Open the airway by placing one had under the neck, the other on the
forehead and tilting the head back, figure ii. Transfer your hand form the
neck to the chin and push upwards. Breathing may start. If so place in
recovery position.

Figure ii

(iii) If the casualty is still not breathing, take a deep breath, pinch the
casualty’s nostrils together with your fingers and seal your lips around
his/her mouth. Blow air into the lungs and watch the chest rise until it has
fully expanded, figure iii.
(iv) Remove mouth well way and breathe out excess air. Watch chest fall.

103
Figure iii

(v) Repeat first four inflations as quickly as possible without waiting for lungs
to deflate completely. Check the pulse at the neck (carotid) to ensure the
heart is beating, figure iv.

Figure iv – Carotid Pulse

(vi) If the heat is beating normally, continue inflations at natural breathing rate
(16-18 per minute) until normal breathing is restored. Place casualty in the
recovery position.

(vii) IF AFTER FOUR VENTILATIONS the casualty does not respond,

start external chest compression.

Kneel alongside the casualty facing the chest. Place the heel of your hand
on the centre of the lower hand of the breastbone. Cover this with the heel
104
 of your other hand and lock the fingers together. With arms straight, press
vertically down on the lower half of the breast bone to depress chest about
4cm (1.5in), Figure v. Do this 15times at the rate of 80 per minute.

Figure v
Reopen the airway and give two ventilations. Repeat the 15 compressions
and two ventilations or one minute and check carotid pulse. If present, stop
compressions. Continue with inflation until breathing is restored, then
place casualty in recovery position. If the pulse is absent, repeat cycles,
checking for heart-beat every three minutes or 12 cycles.

3.2 Manual Artificial Ventilation Method – Speed is Essential

(i) Check airway is not blocked. Turn head to one side and remove
obstructions around the face and neck any debris in mouth.

(ii)Open the airway by placing one hand under the neck, the other on
the forehead and tilting the head back, Figure ii. Transfer your hand
from the neck to the chin and push upwards. Breathing may start. If
so place in recovery position.

(iii) If the casualty is still not breathing and mouth to mouth ventilation
is not possible (i.e. if there are sever facial injuries) the casualty
should be tuned face down with the hands placed under the head.
Turn the head sideways and ensure that the airway is open. Kneel in
front of the casualty’s elbows. Put your hands on the shoulder
blades ensuring that the thumbs are on either side of the spine,
figure vi. With your elbows straight rock forward until your arms
are vertical and sustain pressure for two seconds. Rock backwards
allowing your arms to slide back and grab the casualty’s arms just
105
 above the elbows. Raise the arms and pull until tension is felt and
hold for three seconds.

Figure vi

Be careful not to overstretch. Repeat 12 times per minute. After 4

manual ventilations check the pulse at the neck (carotid) to ensure
the heart is beating, Figure iv.

(iv) If the heart is beating normally, continue inflations at 12 times per

minute until normal breathing is restored. Place casualty in the
recovery position.

(v) IF AFTER FOUR VENTILATIONS the pulse is not present,

start external chest compression.
Turn casualty over and kneel alongside facing the chest. Place the heel
of your hand on the centre of the lower half of the breastbone. Cover
this with the heel of your other hand and lock the fingers together. With
arms straight, press vertically down on the lower half of the breast bone
to depress about 4cm (1.5in), Figure v. do this 15 times at the rate of 80
per minute.
Turn casualty over, reopen the airway and give two manual
ventilations. Repeat the 15 compressions and two manual ventilations
for minute and check carotid pulse. If present, stop compressions.
Continue with inflation until breathing is restored, then place casualty
in recovery position. If the pulse is absent, repeat cycles, checking for
heart-beat every three minutes or 12 cycles.

APPENDIX II - PERMIT-TO-WORK
Local No ……
N.C.C No ……

106
PERMIT-TO-WORK ON PLANT AND EQUIPMENT UNDER THE
CONTROL OF THE AUTHORITY.
This document shall be issued to a Competent Person in charge of work and
shall be retained by him/her until cleared.
This plant or equipment must not be made live until this document is cancelled.

1. ISSUE
1.1 Issued to: …………………………………………………………….
In the employ of: ……………………………………………………
1.2 work to be carried out: ……………………………...........................
………………………………………………………………………
1.3 Plant or equipment to be worked on: ……………………………….
……………………………………………………………………....
………………………………………………………………………
1.4 Points of isolation: …………………………………………….....
………………………………………………………………………..
………………………………………………………………………..
……………………………………………………………………...
1.5 Nearest points live: …………………………………………….
…………………………………………………………………….
……………………………………………………………………
1.6 Circuit main earths have been connected at the following points
…………………………………………………………………….
…………………………………………………………………….
……………………………………………………………………
1.7 Danger Notices: ………………………………………………...
………………………………………………………………….
………………………………………………………………….
1.8 Caution Notices: ……………………………………………….
………………………………………………………………….
…………………………………………………………………
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1.9 Special Keys: …………………………………………………
…………………………………………………………………
Other precautions: …………………………………………….
…………………………………………………………………...
1.10 No. of additional earths issued: ………………………………..
1.11 No of circuit identity wristlets issued: ………………………….
1.12 Issued with consent of Controller
Name of Controller: ………………………………………..
Time: ……………… Hours Date: ………………………
1.13 I declare that it is safe to work on the plant or equipment which is
dead, isolated from all live conductors and is earthed.

Issuing Senior Authorised Person

Name: …………………………………………………………….
Signature: …………………………………………………………
time: …………………….. Hours Date: ……………………

2.0 DECLARATION BY RESPONSIBLE OFFICIAL TO BE

COMPLETED IN TERMS OF SAFETY RULE 17.1 (c), WHERE
APPLICABLE
I have read this Permit-to-Work and I certify that where applicable the
plant or equipment is dead and isolated on these premises. Safety devices
and circuit main earths will not be removed until Permit-to-Work has
been cancelled and permission has been obtained from the Senior
Authorised Person of the Authority.

Name: ………………………………………………………………………

In the employ of: …………………………………………………………..

Designation: ……………………………………………………………….

108
 Signature: …………………………………………………………………

Time: ……………………….. Hours Date: …………………………..

3.0 RECEIPT
This Section must be signed before work can commence. The Permit-to-
Work must be retained by the signatory who must be Competent Person
in charge of the work, until the work has been suspended or completed and
Section 4 has been signed.
I declare that I accept responsibility for carrying out work on the plant or
equipment detailed on this Permit-to-Work and that no attempt will be
made by me or by any person under my control to carry out work on any
other plant or equipment. I shall not leave the site of work while work is in
progress.

Name of Competent Person in charge of the work: ………………………

Signature: …………………………………………………………………
Time: ……………………… Hours Date: ………………………………

4.0 CLEARANCE
I declare that all person under my control have been withdrawn and warned
that it is no longer safe to work on the plant or equipment specified in this
Permit-to-Work, and that all tools, materials and additional earths are
clear.
I declare that I have checked in …………… additional earths and
……….. circuit identity wristlets.
Signature of Competent Person in charge of the work:
……………………
Time: …………………. Hours Date: ……………………………….

109
5.0 CANCELLATION
I declare that this Permit-to-Work has been cancelled with the consent of
the Controller.
Name of Controller: ……………………………………………………..
Time: ………………….. Hours
Name of Senior Authorised Person: ………………………………………
Signature: ………………………………………………………………..
Time: ………………………. Hours Date: ………………………

6.0 DECLARATION BY RESPONSIBLE OFFICIAL

This section must be completed if Section 2 has been completed.

I have been told by Senior Authorised Person that this Permit-to-Work

has been cancelled.
Name: ………………………………………………………………………
Designation: ………………………………………………………………
Signature: …………………………………………………………….
Time: ………………………. Hours Date: ………………………..

7.0 INDIRECT ISSUE

I have read Section of the Permit-to-Work to (Name):
…………………………………. being the Competent Person in charge
of the work who has confirmed that he/she has made an accurate copy of
the Permit-to-Work and has signed Section 3.

110
 Name of Senior Authorised Person……………………………………..
……………………………………………………………………………
Signature: …………………………………………………………………
Time: …………………………. Hours Date: ………………………..

8.0 INDIRECT CLEARANCE

(Name) …………………………………………………….being the
Competent Person in charge of the work has confirmed that he/she has
completed Section 4 of his/her Permit-to-Work copy, and has read it to
me.

Name of Senior Authorised Person: …………………………...................

…………………………………………………………………………........
Signature: ………………………………………………………………
Time: ………………………….. Hours Date: ………………………..

9.0 WORKER’S DECLARATION

9.1 I/We, the undersigned, declare that the plant or equipment on which it is
safe to work has been shown to us.
NO. DATE TIME NAME SIGNATURE

1
2
3
4
5
6
7
8
9
10
11
12
13
14
111
15
16
17
18
19
20

9.2 I/We have been told that it is no longer safe to continue working on the
plant or equipment.

NO. DATE TIME NAME SIGNATURE

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
APPENDIX III – SANCTION-FOR-TEST
Local No: ………
N.C.C No.: ………
SANCTION-FOR-TEST- ON PLANT AND EQUIPMENT UNDER THE
CONTROL OF THE AUTHORITY

112
1. ISSUE
1.1 Issued to: …………………………………………………………….
In the employ of: ……………………………………………………
1.2 work to be carried out: ……………………………...........................
………………………………………………………………………
1.3 Plant or equipment to be tested on: ……………………………….
……………………………………………………………………....
………………………………………………………………………
1.4 Points of isolation: …………………………………………….....
………………………………………………………………………..
………………………………………………………………………..
……………………………………………………………………...
1.5 Nearest points live: …………………………………………….
…………………………………………………………………….
……………………………………………………………………
1.6 Circuit main earths have been connected at the following points
…………………………………………………………………….
…………………………………………………………………….
……………………………………………………………………
1.7 Danger Notices: ………………………………………………...
………………………………………………………………….
………………………………………………………………….
1.8 Caution Notices: ……………………………………………….
………………………………………………………………….
…………………………………………………………………
1.9 Special Keys: …………………………………………………
…………………………………………………………………
Other precautions: …………………………………………….
…………………………………………………………………...
1.10 No. of additional earths issued: ………………………………..
113
1.11 Issued with consent of Controller
Name of Controller: ………………………………………..
Time: ……………… Hours Date: ………………………
1.12 I declare that the plant or equipment has been isolated from the
remainder of the system, and must not be reconnected at any point
without the sanction of the Controller. Work on and operation of
any part of the isolated plant or equipment must be carried out in
strict accordance with the Authority’s Safety Rules. The recipient of
this form may remove circuit main earths and make it live from a
test supply but he/she will be responsible for coordinating all such
operations on isolated plant or equipment and ensuring safety during
the tests.

Issuing Senior Authorised Person

Name: …………………………………………………………….
Signature: …………………………………………………………
time: …………………….. Hours Date: ……………………

2.0 DECLARATION BY RESPONSIBLE OFFICIAL TO BE

COMPLETED IN TERMS OF SAFETY RULE 17.1 (C), WHERE
APPLICABLE.

I have read this Sanction-for-Test and I certify that where applicable the
plant or equipment is dead and isolated on these premises. Safety devices
and circuit main earths will not be removed until Sanction-for-Test has
been cancelled and permission has been obtained from the Controller as
provided for under Rule 17.4 (c).

Name: ………………………………………………………….

In the employ of: ……………………………………………...

Designation: …………………………………………………..

114
 Signature: …………………………………………………….

Time: ………………………….. Hours Date: ……………….

3.0 RECEIPT
This Section must be signed before work can commence. The Sanction-
for-Test must be retained by the signatory who must be the Senior
Authorised Person in charge of the work, until the work has been
suspended or completed and Section 4 has been signed.
I declare that I accept responsibility for carrying out the testing on the plant
or equipment detailed on this Sanction-for-Test that I am personally
responsible for taking the necessary safety precautions to avoid danger,
and that no attempt will be made by me or by any person under my control
to carry out work on any other plant or equipment. I shall not leave the site
of work while work is in progress.

Name of Senior Authorised Person in charge of the work:

…………………………………………………………………………….
Signature: …………………………………………………………………
Time: ……………………… Hours Date: ………………………………

4.0 CLEARANCE
I declare that all person under my control have been withdrawn and warned
that it is no longer safe to work on the plant or equipment specified in this
Sanction-to-Test, and that all tools, materials and additional earths and
other connections are clear. The isolated plant and equipment has been
returned to its condition at the time of issue of the Sanction-for-Test with
exceptions noted below.
Exceptions:
………………………………………………………………………………
………………………………………………………………………………
…………………………………………………………

115
 Signature of Senior Authorised Person in charge of the work:
……………………………………………………………………………
Time: …………………. Hours Date: ……………………………….

5.0 CANCELLATION
I declare that this Sanction-for-Test has been cancelled with the consent
of the Controller.
Name of Controller: ……………………………………………………..
Time: ………………….. Hours
Name of Senior Authorised Person:
………………………………………
Signature: ………………………………………………………………..
Time: ………………………. Hours Date: ………………………

6.0 DECLARATION BY RESPONSIBLE OFFICIAL

This section must be completed if Section 2 has been completed.

I have been told that this Sanction-for-Test has been cancelled.

Name: ………………………………………………………………………
Designation: ………………………………………………………………
Signature: …………………………………………………………….
Time: ………………………. Hours Date: ………………………..

7.0 WORKER’S DECLARATION

116
7.1 I/We, the undersigned, declare that the plant or equipment on which it is
safe to work has been shown to us.
NO. DATE TIME NAME SIGNATURE

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
7.2 I/We have been told that it is no longer safe to continue working on the
plant or equipment.

NO. DATE TIME NAME SIGNATURE

1
2
3
4
5
6
7
8
9
10
11

117
12
13
14
15
16
17
18
19
20

APPENDIX IV – LIMITATION-OF-ACCESS
Local No.: ……

THIS DOCUMENT MUST BE USED FOR WORK ON PLANT AND

EQUIPMENT FOR WHICH A PERMIT-TO-WORK OR SANCTION-FOR-
TEST IS NOT REQUIRED.

This document shall be issued to a Competent Person in charge of work and shall
be retained by him/her until.

1.0 ISSUE

1.1 Issued to: ………………………………………………………

In the employ of: ………………………………………………
…………………………………………………………………
1.2 Nature of Work: ………………………………………………..
………………………………………………………………….
………………………………………………………………….
………………………………………………………………….
1.3 Location: ……………………………………………………….
Plant or Equipment or Area: …………………………………...
…………………………………………………………………..
1.4 Limit of Access: ………………………………………………
………………………………………………………………...
………………………………………………………………...
1.5 Other Precautions: ……………………………………………
………………………………………………………………..
………………………………………………………………..
………………………………………………………………..
1.6 Name of Controller notified: ………………………………...
118
 Time: ……………… Hours Date: ……………………….
1.7 I declare that it is safe to work in the area or on the plant or
equipment and that work must not be carried out on any other plant
or equipment in any other area outside the limit of access.
Issuing Senior Authorised Person
Name: ……………………………………………………….
Signature: …………………………………………………..
Time: …………………………. Hours Date: …………………

2.0 RECEIPT
This Section must be signed before work can commence. The copy
of the Limitation-of-Access must be retained by the signatory who
must be the Competent Person in charge of the work, until the
work has been suspended or completed and Section 3 has been
signed.

I declare that I accept responsibility for carrying out work on the

plant or equipment or in the area detailed on this Limitation-of-
Access and that no attempt will be made by me or by any person
under my control to carry out on any other plant or equipment or in
any other area. I shall not leave the site or work is in progress.

Name of Competent Person in charge of the work:

……………………………………………………………………….
Signature: …………………………………………………………...
Time: …………………… Hours Date: ……………………….

3.0 CLEARANCE
I hereby declare that all persons under my charge have been withdrawn and
no more work will be carried the terms of this Limitation-of-Access
document.

Name of Competent Person in charge of the work:

……………………………………………………………………………
Signature: ………………………………………………………………….
Time: …………………. Hours Date: ……………………………….

119
4.0 CANCELLATION
4.1 I declare that this Limitation-of-Access has been cancelled with the
consent of the Controller.
4.2 Name of Senior Authorised Person:
………………………………………
………………………………………………………………………………
Signature: …………………………………………………………………
Time: ………………….. Hours Date: ……………………………..
Name of Controller notified: ……………………………………………
Time: ………………………. Hours Date: ………………………

5.0 WORKER’S DECLARATION

5.1 I/We, the undersigned, declare that the plant or equipment on which it is
safe to work has been shown to us.
NO. DATE TIME NAME SIGNATURE

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

120
18
19
20

5.2 I/We have been told that it is no longer safe to continue working on the
plant or equipment.

NO. DATE TIME NAME SIGNATURE

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

APPENDIX V – VISITOR’S LIVE ENCLOSURE PERMIT

No.: …………………..

We, the undersigned persons, not being employees of the authority, hereby
declare that we thoroughly understand that it is dangerous to approach within 1
metre (three feet) of any portion of the plant or equipment contained within the
enclosure(s) we are about to enter, and we hereby agree that to enter the said
enclosure entirely at our own risk, and that we shall have no action against the
Authority should we sustain any injury while in or about the said enclosure(s).

121
 Name Signature
1 ………………………………….. ………………………………………….
2 …………………………………. ………………………………………….
3 ………………………………… ………………………………………….
4 ………………………………… …………………………………………
5 ………………………………… …………………………………………
6 ………………………………… …………………………………………
7 ………………………………... …………………………………………
8 ………………………………… …………………………………………
9 ………………………………… ………………………………………….
10 ……………………………….. ………………………………………….

Official authorized to accompany visitors:

Name: ……………………………………………………………………………
Signature: ……………………………………………………………………….
Designation: ……………………………………………………………………..
Date: ………………………. Time: ……………………………………

APPENDIX VI – MINIMUM HEIGHTS OF OVERHEAD LINES AT

ROAD AND RAILWAY CROSSING POINTS

RATED VOLTAGE OVER ROADS OVER RAILWAYS

Up to and including 33kV 5.8 m 10.5 m
66kV 6.0 m 10.9 m
88kV 6.1 m 11.1 m
110 kV and 132kV 6.7 m 11.5 m
220kV 7.0 m 12.4 m
330kV and 400Kv 7.3 m 13.4 m

The height for any intermediate rated voltage shall be that applicable to the next
higher rated voltage.

FORM E.18
ZIMBABWE ELECTRICITY SUPPLY AUTHORITY
PERMIT-TO-WORK (Second Edition, 1998)
No 4689
122
PERMIT-TO-WORK ON PLANT AND EQUIPMENT UNDER THE CONTROL OF THE AUTHORITY Local No. NR:…..
This document shall be issued to a Competent Person in charge of work and shall be retained by him/her until cleared.
This plant or equipment must not be made live until this document is cancelled. N.C.C. No. ………

1.0 ISSUE ……………………………………….

1.1 Issued to: ……………………………………….
………………......................... 1.8 Caution notices: …………………
In the employ of: …………………………………..
…………………......... ……………………………………
Work to be carried out: 1.9 Special keys: .................................
……………….. ……………………………………
……………………………………… …………………………………….
……………………………………… ……………………………………..
……………………………………… 1.10 Other precautions: ...........................
……… ……………………………………..
1.3 Plant or equipment to be worked on: ……………………………………..
………………………………............... ……………………………………..
............................................................... 1.11 No. of additional earths issued: .......
... ……………………………..............
1.4 Points of isolation: 1.12 No. of circuit identity wristlets issued:
…………………..... ………………………………………
……………………………………… Issued with consent of Controller
……………………………………… Name of Controller:
……………………………………… ……………………
……… Time: ………… Hours Date:
1.5 Nearest points live: ………......
……………………
1.13 I declare that it is safe to work on the
plant or equipment which is dead,
………………………………………… isolated live conductors and is earthed.

Issuing Senior Authorised Person

…………………………………………
Name: ……………………………
……………………………………
Signature: ………………………..
1.6 Circuit main earths have been
Time: …........ Hours Date: ………………
connected at the following points:
………………………………………
…
2.0 DECLARATION BY
……………………………………… RESPONSIBLE OFFICIAL TO BE
…………………………....................... COMPLETED IN T**** OF SAFETY
RULE 17.1 (C), WHERE APPLICABLE.
....
1.7 Danger notices: ………………………
123
I have read this Permit-to-Work and I certify I declare that I have checked in ……………
that where applicable the plant or equipment is additional earths and …………….. circuit
dead and isolated these premises. Safety identity wristlets.
devices and circuit main earths will be removed
until Permit-to-Work has been cancelled and Signature of Competent Person in charge of the
permission has been obtained from the Senior work: ………………………
Authorised Person of the Authority.
Time: ………. Hours Date: ……………..
Name: ……………………………………
In the employ of: ………………………..
5.0 CANCELLATION
Designation: ……………………………..
Signature: ……………………………….. I declare that this Permit-to-Work has been
Time: ………. Hours Date: …………….. cancelled with the consent of the Controller.

Name of Controller: ………………………..

3.0 RECEIPT Time: ……………. Hours

This Section must be signed before work can Name of Senior Authorised Person:
commence. The Permit-to-Work must have ………………………………………………
retained by the signatory who must be the
Competent Person in charge of the work, the Signature: …………………………………
work has been suspended or completed and
Section 4 has been signed. Time: …………….. Hours Date: …………

I declare that I accept responsibility for

carrying out work on the plant or equipment
6.0 DECLARATION BY
detailed on this Permit-to-Work and that no
RESPONSIBLE OFFICIAL
attempt will be made by me or by any person
under my control to carry out work on any
This Section must be completed if Section 2
other plant or equipment. I shall not leave site
has been completed.
of work while work is in progress.
I have been told by the Senior Authorised
Name of Competent Person in charge of work:
Person that this Permit-to-Work has been
……………………………………… cancelled.
Signature: …………………………………
Name: ……………………………………..
Time: ………….. Hours Date: …………….
Designation: ……………………………..

4.0 CLEARANCE Signature: ………………………………….

I declare that all persons under my control have Time: ………….. Hours Date:
been withdrawn and warned that it is no longer …………………
safe to work on the plant or equipment
specified in this Permit-to-Work and that all
tools, materials and additional earths are clear. 7.0 INDIRECT ISSUE

I have read Section 1 of the Permit-to-Work to

(Name) ………………………………….being

124
the Competent Person in charge of the work 13
who has confirmed that he/she has made an 14
accurate copy of the Permit-to-Work and has 15
signed Section 3. 16
17
Name of Senior Authorised Person: 18
………………………………………………… 19
. 20

Signature: 9.2 I/ We have been told that it is no longer

……………………………………… safe to continue working on the plant or
equipment.
Time: ………………. Hours Date:
……………. DATE TIME NAME SIGNATURE
1
2
3
8.0 INDIRECT CLEARANCE
4
5
(Name) ……………………………….being 6
the Competent Person in charge of the work has 7
confirmed that he/she has completed Section 4 8
of his/her Permit-to-Work, copy and has read it 9
to me. 10
11
Name of Senior Authorised Person: 12
………………………………………………… 13
. 14
15
Signature: …………………………………….. 16
17
Time: ………….. Hours Date: …………….. 18
19
20
9.0 WORKER’S DECLARATION

9.1 I/We, the undersigned, declare that the

plant or equipment on which it is safe to work
has been shown to us.

DATE TIME NAME SIGNATURE

1
2
3
4
5
6
7
8
9
10
11
12

125
RM E-96A No 0731
ZIMBABWE ELECTRICITY SUPPLY AUTHORITY
SANCTION-FOR-TEST (Second Edition, 1998)
Local No. NR:
…….....
N.C.C. No:
…………..

SANCTION-FOR-TEST ON PLANT AND EQUIPMENT UNDER THE CONTROL OF

THE AUTHORITY

ISSUE ………………………………………………..
Issued to: …………………………………… ……………………………………………….
In the employ of: …………………………… Danger Notices: …………………………….
Work to be carried out: …………………….. ………………………………………………
………………………………………………. ……………………………………………....
Plant or equipment to be tested: ……………. Caution notices: …………………………….
………………………………………………. ………………………………………………
……………………………………………..... ………………………………………………
Points of isolation: …………………………. Special Keys: ………………………………
……………………………………………… ………………………………………………
……………………………………………... Other Precautions: ………………………….
……………………………………………… ………………………………………………
Nearest points live: ………………………… 1.10 No. of additional earths issued: ………
……………………………………………… 1.11 Issued with consent of Controller
……………………………………………… Name of Controller:
……………………………………………… ……………………
Circuit main earths have been connected at the Time: ……………………… Hours
following points: ……………………………..

126
1.12 I declare that the plant or equipment Time: ……………… Hours Date:
has been isolated from the remainder of the ……………
system, and must not be reconnected at any
point without the sanction of the Controller.
Work on and operation of any part of the
isolated plant or equipment must be carried out 3.0 RECEIPT
in strict accordance with the Authority’s Safety
Rules. The recipient of this form may remove This Section must be signed before work can
circuit main earths and make it live from a test commence. The Sanction-for-Test must be the
supply but he/she will be responsible for Senior Authorised Person in charge of the
coordinating all such operations on isolated work, until the work has been suspended or
plant or equipment and ensuring safety during completed and Section 4 has been signed.
tests.
I declare that I accept responsibility for
Issuing Senior Authorised Person carrying out the testing on the plant or
equipment detailed on this Sanction-for-Test,
Name: ………………………………………… that I am personally responsible for taking the
Signature: …………………………………….. necessary safety precautions to avoid danger,
and that no attempt will be made by me or by
Time: ……………….. Hours Date:…………..
any person under my control to carry out work
on any other plant or equipment. I shall not
leave the site of work while work is in progress.
2.0 DECLARATION BY
RESPONSIBLE OFFICIAL TO BE Name of Senior Authorised Person in charge of
COMPLETED IN TERMS OF the work:
SAFETY RULE 17.1 (c) WHERE
………………………………………..
APPLICABLE.
Signature:
I have read this Sanction-for-Test and I certify ……………………………………….
that where applicable plant or equipment is
Time: ……………. Hours Date:
dead and isolated on these premises. Safety
devices and circuit main earths will not be ……………….
removed until Sanction-for-Test has been
cancelled and permission has been obtained
from the Controller as provided for under Rule
17.4 (c). 4.0 CLEARANCE

Name:
I declare that all persons under my control have
………………………………………….. been withdrawn and warned that it is no longer
In the employ of: safe to work on the plant or equipment
………………………………. specified in this Sanction-for-Test, and that all
tools, materials, additional earths and other
Designation: connections are clear. The isolated plant and
…………………………………… equipment has been returned to its condition at
Signature: the time of issue of the Sanction-for-Test with
exceptions noted below.
………………………………………
Exceptions: ……………………………………

127
………………………………………………… Time: …………… Hours Date:
………………………………………………… ……………….
…………………………………………………
Signature of Senior Authorised Person in
7.0 worker’s declaration
charge of the work:
……………………………………. 7.1 I/We, the undersigned, declare that the
plant or equipment on which it is safe to work
Time: …………… Hours Date:
has been shown to us.
………………
DATE TIME NAME SIGNATURE
1
2
5.0 CANCELLATION 3
4
I declare that this Sanction-for-Test has been 5
cancelled with the consent of the Controller. 6
7
Name of Controller: 8
9
……………………………. 10
Time: …………………………. Hours 11
12
Name of Senior Authorised Person: 13
……………. 14
15
…………………………………………………
16
.. 17
Signature: 18
19
……………………………………… 20
Time: ………….. Hours Date:
7.2 I/ We have been told that it is no longer
……………….. safe to continue working on the plant or
equipment.

6.0 declaration by responsible official DATE TIME NAME SIGNATURE

1
2
This section must be completed if Section2 has
3
been completed.
4
5
I have been told that this Sanction-for-Test has
6
been cancelled.
7
8
Name:
9
…………………………………………... 10
Designation: 11
12
……………………………………. 13
Signature: 14
15
………………………………………. 16
17
128
18
19
20

ZIMBABWE ELECTRICITY SUPPLY AUTHORITY

LIMITATION-OF-ACCESS (SECOND EDITION, 1998)

THIS DOCUMENT MUST BE USED FOR WORK ON PLANT AND EQUIPMENT FOR WHICH A PERMIT-
TO-WORK OR SANCTION-FOR-TEST IS NOT REQUIRED

129
Consent shall be issued to a Competent Person in charge of work and shall be retained by him/her

Local No. NR 23855

I declare that it is safe to work in the area or on
the plant or equipment and that work must be
1.0 ISSUE
carried out on any other plant or equipment in
1.1 Issued to : …………………………… any other area outside the limit of access:
In the employ of:
Issuing Senior Authorised Person
………………………
Name:
………………………………………
…………………………………………..
…
Signature:
1.2 Nature of Work: ………………………
………………………………………
………………………………………
Time: ………….. hours Date:
…
……………….
………………………………………
…
Location: 2.0 RECEIPT
………………………………
This Section must be signed before work can
Plant or Equipment or Area: commence. The copy of the Limitation-of-
…………… Access must be retained by the signatory who
must be the Competent in charge of the work,
……………………………………… until the work has been suspended or
… completed and Section 3 has been signed.

1.3 Limit of Access: ……………………… I declare that I accept responsibility for

……………………………………… carrying out work on the plant or equipment or
on in the area detailed on this Limitation-of-
… Access and that no attempt will be made by me
……………………………………… or by any person under my control to carry out
work on any other plant or equipment or in any
… other area. I shall not leave the site of work
1.5 Other Precautions: while work is in progress.

……………………. Name of Competent Person in charge of the

……………………………………… work:
……………………………………… ……………………………………………
…… Signature:
……………………………………… ……………………………………….
… Time: ………….. Hours Date:
1.6 Name of Controller notified: ………… ……………….
………………………………………
…
Time: ……………… Hours Date: 3.0 CLEARANCE
……………

130
I hereby declare that all persons under my 3
charge have been withdrawn and no more work 4
will be carried out under the terms of this 5
Limitation-of-Access document. 6
7
Name of Competent in charge of the work: 8
…….. 9
1
………………………………………………… 0
.. 1
1
Signature: 1
……………………………………… 2
1
Time: ……………….. Hours Date:
3
…………… 1
4
1
5
4.0 CANCELLATION 1
6
4.1 I declare that this Limitation-of-Access 1
has been cancelled. 7
1
4.2 Name of Senior Authorised Person:
8
……
1
………………………………………
9
… 2
0
Signature:
……………………………… 9.2 I/ We have been told that it is no longer
Time:……… Hours Date: safe to continue working on the plant or
equipment.
……………
Name of Controller notified: DAT TIM NAM SIGNATUR
E E E E
………….
1
2
…………………………………………. 3
4
Time: ………….. Hours Date: 5
……….. 6
7
8
5.0 WORKER’S DECLARATION 9
1
5.1 I/We, the undersigned, declare that the 0
plant or equipment or area on which it 1
is safe to work has been shown to us. 1
1
2
DAT TIM NAM SIGNATUR
1
E E E E
3
1
1
2
131
 4
1
5
1
6
1
7
1
8
1
9
2
0

ZIMBABWE ELECTRICITY SUPPLY AUTHORITY

LIVE LINE PERMIT-TO-WORK
LOCAL No
………..
NCC
No…………….

LIVE LINE PERMIT-TO-WORK ON ENERGIZED PLANT AND EQUIPMENT

UNDER THE CONTROL OF THE AUTHORITY

This document shall be issued to a Live Line Linesman in charge of the work and shall be
retained by him until the work is completed or stopped.

1.0 ISSUE
1.1 Issued to: ……………………………….. In the employ of
………………………………..
1.2 Work to be carried out:
…………………………………………………………………….

……………………………………………………………………...
1.3 Equipment to be worked on:
………………………………………………………………

……………………………………………………………..
1.4 I declare that all auto-reclose devices:
……………………………………………………
have been switched off and Live Line: ………………………………………………….

132
 Caution Notices have been placed at the following location:
…………………………….
1.5 I declare that it is safe to work to within ……….m of the high voltage conductors as
specified in Table1, Absolute Limits for Qualified Live Line crew, Rule 7.1.
1.6 Special keys or …………………………………………………………
other precautions …………………………………………………………
1.7 No. of circuit identity wristlets issued: ……………………………………………….
1.8 Issued with consent of Controller (Name): ……………………………………………
1.9 Issuing Senior Authorised Person:
Name: …………………………………….. Signature: ………………………………
Time: …………………. Hrs Date: ……………………………………………

2.0 RECEIPT

This Section must be signed before work can commence. The Live Line Permit-to-
Work must be retained by the signatory, who must be the Live Line Linesman in charge
of the work, until the work has been completed and Section 4 has been signed. I declare
that I accept responsibility for carrying out work on the apparatus detailed on this Live
Line Permit-to-Work and that no attempt will be made by me or by any person under
my control to carry out work on any other equipment. I shall not leave the site of work
while work is in progress.

Name of person in charge of work………………………….

Signature……………………

Time: ……………………………. hrs Date: ……………………….............

3.0 SUSPENSION / RESUMPTION OF WORK

3.1 I declare that Live Line work on the equipment specified in this Live Line Permit-to-
Work is suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.2 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Live Line Permit-to-Work.

133
 Name of person in charge of work…………………………. Signature
……………………
Time: ……………………………. hrs Date:
……………………….

3.3 I declare that Live Line work on the equipment specified in this Live Permit-to-Work is
suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.4 I declare that I accept responsibility to resume Live Line work on the equipment as
specified I this Live Line Permit-to-Work.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.5 I declare that Live Line work on the equipment specified in this Live Lime Permit-to-
Work is suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.6 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Live Line Permit-to-Work.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.7 I declare that Live Line work on the equipment specified in this Live Line Permit-to-
Work is suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.8 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Live Line Permit-to-Work.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

134
3.9 1 declare that Live Line on the equipment specified in this Live Line Permit-to-Work is
suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.10 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Line Permit-to-Work.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

4.0 CLEARANCE

I declare that all persons under my control have been withdrawn and warned that it is
no longer safe to work on the equipment specified in tis Live Line Permit-to-Work, and
that all equipment is clear.

I declare that I have checked in: ………………………………………………………..

circuit identity wristlets.

Name of Live Line Linesman in charge of work: …………………...

……………………
Signature:
…………………………
Time: ………………………… hrs Date:
………………………………

5.0 CANCELLATION

I declare that this Live Line Permit-to-Work has been cancelled with the consent of the
Controller.

Name of Controller: ………………………………………………

Name of Senior Authorized Person: …………………... Signature: ……………………

135
 Time: ………………………… hrs Date: …………………………….

6.0 INDIRECT ISSUE

I have read Section 1 of the Live Line Permit-to-Work to:

……………………………… being the Live Line Linesman in charge of the work who
has confirmed that he has made an accurate copy of the Love Line Permit-to-Work and
has signed Section 2.

Name of Senior Authorised Person: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

7.0 INDIRECT CLEARANCE

……………………………………………being the Live Line Linesman in charge of
the work has confirmed that he has completed Section 4 of the Live Line Permit-to-
Work Record, and has read it to me.

Signature of Senior Authorised Person:

…………………………………………………..
Time: ………………… hours Date:
………………………………

Form E.10 Electricity Safety Rule No: 8.2

ZIMBABWE ELECTRICITY DISTRIBUTION COMPANY

No: ………………………..

CONTROLLER’S INSTRUCTION FORM

51800

………………

Date: ………………………………………
District of Station: ……………………………………………………………………………..
Instruction Issued By: …………………………………… At: ……………………………..
Instructions Received By: ………………………………. At: ……………………………..
Instructions related to the following substations, line or apparatus: ………………………….

136
…………………………………………………………………………………………………
…………………………………………………………………………………………………
Instructions given *verbally* by telephone/*radio-telephone/*writing.
Time
INSTRUCTIONS RECEIVED OR ISSUED

SUBTITLE
705612
SIGNATURE: …………………………………………………………………..
NAME: …………………………………………………………………………
Delete whichever is not applicable

ZIMBABWE ELECTRICITY SUPPLY

AUTHORITY

137
 LIVE LINE SAFETY RULES

SUPPLEMENT

FIRST EDITION, 1990

FOR THE PERFORMANCE OF LIVE LINE WORK

ON THE AUTHORITY’S ENERGIZED EQUIPMENT.

A. - GENERAL

B. - LIVE LINE DAFETY RULES

I ACKNOWLEDGEE RECEIPT OF THIS COPY

FULL NAME ………………………………………………

SIGNATURE ………………………………………………

DATE ………………………………………………

ZIMBABWE ELECTRICITY SUPPLY

ELECTRICITY

138
 LIVE LINE SAFETY RULES
(SUPPLEMENT)

FIRST EDITION, 1990

FOR THE PERFORMANCE OF LIVE LINE WORK

ON THE AUTHORITY’S ENERGIZED EQUIPMENT

A. GENERAL

1.0 Supplementary Rules:

These Safety Rules are issued as a supplement to the Electrical Safety and must be read
and understood as such. Employees performing Live Line work or required to issue
Live Line permits-to-work must be fully aware of and conversant with both the
Electrical Safety Rules and the Live Line Safety Rules (Supplement).

2.0 Definitions:

2.1 Approved - sanctioned by the General Manager or by his authorized representative.

2.2 Absolute Minimum Working Clearance - the minimum distance between any part
of a worker’s body and the energized line or equipment and is applicable ONLY to
trained and qualified Live Line Linesmen. Refer to Table 1 and Figure 1.

ZIMBABWE ELECTRICITY SUPPLY

AUTHORITY

SAFEETY RULES (SUPPLEMENT)

139
 FOR THE PERFORMANCE OF LIVE LINE WORK
ON THE AUTHORITY’S ENERGIZED EQUIPMENT

INTRODUCTION:

The following Rules for the performance of live line work on the Authority’s energized
equipment are designed for the protection of the Authority’s employees and others against
injury in the course of their duties, and to ensure the safe and efficient operation of the
Authority’s plant and equipment.

These rules must be strictly observed by all persons to whom this book is issued and shall
become part of the conditions of service. Ignorance of the Live Line Safety Rules shall not be
accepted as an excuse for negligence of duty.

Any contravention of these rules shall constitute mis-conduct for the purpose of the Authority’s
Employment Regulations, and any persons contravening these rules shall be liable, where
appropriate, to criminal prosecution.

Any person who may perform live line work on the Authority’s equipment will be required to
satisfy representatives of the Authority’s as to his adequate knowledge and understanding of
System Operation procedures and rules in so far as may be applicable to his job.

Any person in doubt as to the interpretation or application of these Rules should refer to the
head of his department.

These safety rules may be revised by the General Manager or his authorized representative.
Any such revisions will be advised in writing to all persons to whom the Live Line Safety
Rules have been issued.

2.3 Controller - a Senior Authorised Person appointed by the Authority to control

power in one of the specific fields of Generation and Transmission, Sub transmission or
Distribution and whose duties are to maintain maximum safety at all times to personnel
and equipment on the Authority’s Power System. The Controller shall approve all
operations on the Authority’s plant and equipment and shall consent to all issues and
cancellations of Permit-to-Work and Sanction-for-Test document.

2.4 Junior Authorised Person - a Competent Person appointed in writing by the

Authority to carry out specific work on the Authority’s Power System in accordance
140
 with his Certificate of Authorisation. A Junior Authorised Person shall not issue or
cancel Permit-to-Work or Sanction-for-Test or Limitation-of-Access documents.

This category includes those involved in Direct Wire Board (DWB) operations such as
may be found in Power Stations, Substations, Control Centres and those under
instructions from a Senior Authorised Person.

2.5 Limits of Approach - this is the minimum distance allowed between the worker, his
tools or the equipment which he is operating and an energized line or equipment. There
are two limits of approach which are significant. One limit is that defined in Rule 18.1
Electrical Safety Rules and is applicable to all persons who have NOT been trained and
qualified in Live Line Work. The other limit is the absolute minimum working
clearance.

2.6 Live Line Caution Notice - is a portable notice in approved form which is placed on
the operating switch of an auto-reclose device or manual reclosing device of a breaker,
or some other switching device. The purpose of the Live Line Caution Notice is to
alert anyone that live line is being performed on the electrical circuit(s) connected to
this device. The Live Line Caution Notice may only be placed by a Senior
Authorised Person after the auto-reclose device has been switched off and on
instruction form the Controller. The Live Line Caution Notice may only be removed
after receiving notice that the Live Line Permit-to-Work has been cancelled. At no
time may a circuit be re-energized after it has opened when a Live Line Crew working
on the lime has been contacted and advised.

2.7 Live Line Crew - is a group of staff specially trained to perform work on
energized lines and equipment.

2.8 Live Line Groundsman - is a person who has been trained to work with the Live
Line Linesman. He is typically required to assist the Live Line Linesman from the
ground by passing up tools, leaning and maintaining tools and other duties as assigned.

2.9 Live Line Linesman - is a person who has been trained and his qualified to perform
work on energized lines and equipment. (Qualified by holding a Live Line Linesman
Certificate)

2.10 Live Line Linesman Certificate - a certificate given to a person who has been
trained by a senior qualified Live Line Linesman and has satisfied the live line
supervisor of his competence.
2.11 Live Line Permit-to-Work - a form declaration signed and given by a Senior
Authorised Person to a Live Line Linesman in charge of the live line work to be
carried out on the Authority’s plant and equipment for the purpose of making known to
that person exactly what points of the supply have has placed on them a Live Line
Caution Notice; what remote control devices have had a Live Line Caution Notice
placed on them; what auto-reclosing, including remote control, have been switched off
or disabled.
141
2.12 Live Line Tools - are tools used by trained and qualified live line linesman to
perform to perform live line work. These tools are specially designed to be electrically
and mechanically suitable for this type of work.

2.13 Live Line Work - is work which is performed on energized lines and equipment
by trained and qualified live line linesman using specially designed tools and live line
work methods which assure that the absolute minimum working clearances are
maintained or adequate protection is provided by approved safety devices.

2.14 Senior Authorised Person - a Competent Person appointed in writing by the

Authority to carry out work on the Authority’s Power System in accordance with his
Certificate of Authorisation.

This category includes the functions of the Junior Authorised Person and all forms of
switching in accordance with the Certificate of Authorisation.

Senior Authorised Person is permitted to issue and cancel Permit-to-Work,

Sanction-for-Test and Limitation-of-Access documents.

2.15 Tailgate Discussion - is a meeting on the job site which takes place prior to
commencing the work. All members of the crew participate in this meeting which is led
by the supervisor or senior live line linesman. The purpose is to ensure everyone
knows what work is to be done, how the work will proceed and who will do what
during the course of the work.

At any time when the work plan must change because of unforeseen circumstances or
situations, a tailgate discussion will be conducted again to ensure that all crew
members understand the new work plan.

At the conclusion of the work, a brief review of the work will be held to look for
improvements on methods, safety, etc.

B. LIVE LINE SAFETY RULES

3.0 PLANNING

3.1 A live line crew must consist of not less than three live line linesmen and one live line
grounds man. If the complexity of the job requires more men, these men shall be
142
 supplied before the job starts. At least two linesmen must be fully qualified in the use of
live line tools for the type of work being performed. No live line maintenance job
which is beyond the ability of the men or the adequacy of the equipment shall be
contemplated.

3.2 Job planning is essential. A tailgate discussion must be held before commencing any
Live Line work. Use of sketches may be advantageous. When delegating portions of
the job, name the individual and make sure he understands. At the completion of each
job, review the method for improvements in safety and betterment of the job.

3.3 Live line work shall not be started during rain or fog, or when the relative humidity is
above eighty percent (80%). If the weather changed before the job is completed, leave
the sticks on the line until the weather clears, then finish the job.

3.4 Arrangements must be made with the Controller giving advance notice, where
possible, for the switching off of the auto-reclose device(s). On lines that are to be
worked, a Live Line Caution Notice shall be placed on the normal and alternative
supply control points. The local controller must be notified on any Live Line work
being performed in the area.

3.5 Tools for the job must be selected with proper voltage rating, mechanical strength and
proper length for the job. When in doubt as to the mechanical strength, use two tools to
support the load.

3.6 Tools to be used must be cleaned and inspected before and after use.

3.7 Live line tools must not be placed on the ground where surface moisture and dirt may
accumulate. Tools must be placed on a rack or tarpaulin.

4.0 INSPECTION OF WORK SITE:

4.1 Inspect structure to be worked on and adjacent structures for missing or bent members,
loose hardware, damaged stay rods or stay wires. Conductors must be checked in
adjacent spans for any damage that could reduce the mechanical strength.

4.2 Ground and side clearances must be checked for conductors to be moved. Check
clearance of trees, buildings, wayleave, roads, railroads and other lines.

5.0 CONDITIONS FOR LIVE LINE WORK

5.1(a) Direct Issue of Live Line Permit-to-Work:

Live Line work shall not be carried out by any person until the Live Line Permit-to-
Work has been signed and a copy handed by a Senior Authorised Person to the
Person in Charge of the work. The Person in charge of the work shall then read its
143
 contents to the Senior Authorised Person issuing the Live Line Permit-to-Work,
sign the copy and its original and retain the copy in his possession until he has signed
the clearance and returned it to a Senior Authorised Person.

5.1(b) Indirect Issue of Live Line Permit-to-Work:

(i) in case of Live Line work, where owing to special circumstances or to the distances
involved the arrangement for direct issue of a Live Line Permit-to-Work would
result in undue delay, the Live Line Permit-to-Work may be issued by a Senior
Authorised Person with the consent of the Controller in accordance with
Electrical Safety Rules, and its contents communicated by him to the Person in
charge of the work by radio or telephone.
(ii) The Person in charge of the work shall enter the details of the Live Line Permit-to-
Work on a Permit or other approved document and shall read the contents to the
Senior Authorised Person for confirmation.

(c) No person in receipt of a Live Line Permit-to-Work may leave the site of the work
while the work is in progress.
(d) A Live Line Permit-to-Work shall be issued to the Live Line Linesman in charge of
each independent Live Line crew.

(e) I any short circuit or other accident occurs during work on or near an energized circuit,
the Controller shall be notified immediately so that assistance may be given or
breakers reclosed to restore supply to the consumer as soon as possible.

6.0 SWITCHING

6.1 (a) Switching for the Live line work shall be carried out under the instruction of a
Controller.

(b) If the circuit is equipped with an automatic reclosing device(s), such device(s) shall be
switched off by the Controller or under his instruction. The Senior Authorised
Person at the local Station shall be instructed to place a Live Line Caution Notice on
the Control panel. In addition to the Live Line Caution Notice or suitable substitute
must be placed on the circuit to be worked on at NCC before the issue of Live Line
Permit-to-Work.

6.2 Live Line Caution Notices:

(a) Live Line Caution Notices are used to indicate to the Operators that in the event of the
breaker tripping, auto-reclose device is switched off and a manual reclosure is
prohibited until assurance is received from the Live Line Permit-to-Work holder or
holders that the workmen are clear and the equipment or circuit is serviceable. Live
Line Permit-to-Work must be cleared immediately upon completion of work or when
no longer required. Live Line Permit-to-Work holder or holders that the workmen are
clear and the equipment or circuit is serviceable. Live Line Permit-to-Work must be
cleared immediately upon completion of work or when no longer required. Live Line
144
 Permit-to-Work may be suspended and resumed later after short periods of absence
form work including overnight stoppages. This shall be recorded on the Live Line
Permit –to-Work.

(b) The use of Live Line Caution Notices shall be limited to the auto-reclosing feature or
manual reclosing features on electrical equipment.

(c) Live Line Caution Notices must be placed on all breakers that could energize the line
or equipment during the period that the Live Line Permit-to-Work is in force.

(d) Live Line Caution Notices shall be removed only after the Live Line crew is clear
from the place of work and the Live Line Permit-to-Work cancelled.

(e) It is important that communication facilities such as a two-way radio be checked when
the location changes. The person in charge of the work group or someone delegated by
him must be available to respond to inquiries from the responsible Controller since the
equipment or circuit may be removed automatically from service by a cause not
involving the work group.

6.3 Recording of switching

A record of all switching and relay operations shall be entered in the appropriate station
or substation log or other approved form. The Controller shall record in his log or
approved form the time and particulars of all switching and relay operations carried out
to his instructions.

The Controller shall also update relevant mimic diagram and single line diagram.

7.0 LIVE LINE WORK CLEARANCES:

7.1 The Limits of Approach Table has been set up as a guide to absolute Minimum
working clearance to be adhered to at all times between any portion of the body and on
the energized conductor.

Care must be taken to maintain these clearances at all times.

The following shall be the limits of approach to live electrical lines, apparatus and
conductors.

TABLE 1: LIMITS OF APPROACH TO LIVE CONDUCTORS AND APPARATUS

CLEARANCES
145
 RATED VOLTAGE Absolute limits for As defined in Rule 18.1
Qualified Electrical Safety Rules
Live Line Crew
Up to and including 33kV .60 m 2.75 m
Exceeding 33kV but not exceeding 66kV .75 m 3.00 m
Exceeding 66kV but not exceeding 132kV 1.05 m 3.50 m
Exceeding 132kV but not exceeding 220kV 1.50 m 4.50 m
Exceeding 220kV but not exceeding 330kV 2.10 m 5.50 m

ABSOLUTE LIMITS OF APPROACH DISTANCES

Under no circumstances shall employees work closer to live electrical lines or apparatus than
the distance specified in the absolute limits for qualified employees (Column 1) unless
adequate protection is provided by approved safety devices.

8.0 SAFETY PRECAUTIONS:

8.1 Choose a safe and comfortable position from which to work. Do not change position
without first looking around and then notify your fellow workers of your intentions.
8.2 Watch your fellow workers. Warn then of close proximity to any energized lines or
equipment.
8.3 Tighten all hand tools and supports, but be careful not to over tighten them.
8.4 Before moving conductor from the insulator, be sure all supports are properly installed
and tight.
146
8.5 The clearance must be carefully watched in adjacent spans when moving conductors.
8.6 when work is being done on an angle structure, additional tools must be used to handle
the strain.
8.7 Link sticks must not be depended upon solely as a means of holding conductor away
from the workman on an angle structure. Holdings tongs and saddles must be used as
well.
8.8 Knots such as square knot, bowline, bowline on a bight, clove hitch or timber hitch
must be used when tying rope on a live line job.
8.9 work only one conductor at a time on the same structure.
8.10 When it is necessary to work on the same phase on different structures, rotation of work
must be coordinated.
8.11 Never carry or hang live line tools on your belts. Tools must be sent up or down on a
handline. Do not hang tools on the conductor being worked on.
8.12 When necessary, rope blocks must be used to support weight and strains on live line
tools. The conductor must be moved slowly and carefully.
8.13 Ground personnel must not stand under the energized conductor that is being moved.
8.14 Live line maintenance must never be hurried. Safety is more important than time.

9.0 COMPLETION OF THE JOB:

9.1 After the necessary maintenance has been completed, and the conductors replaced and
secured, the tools will be lowered to the ground.
9.2 Clean up the work area. Be sure all scrap wire, broken, broken insulators, etc., have
been removed.

10.0 PERSONAL PROTECTION

10.1 Hard hats should be worn at all times by workers and supervisors during field work.
10.2 Leather gloves should be worn when using live line tools. This helps to keep the sticks
dry and clean.
10.3 All linesmen shall use approved safety belts and lanyards where required, to prevent
falls from elevations 3m or more above ground level.
10.4 All workers working with and handling glass or porcelain insulators should wear
approved safety glasses or other eye protection.

ZIMBABWE ELECTRICITY SUPPLY AUTHORITY

147
 LIVE LINE PERMIT-TO-WORK
LOCAL No
………..
NCC
No…………….

LIVE LINE PERMIT-TO-WORK ON ENERGIZED PLANT AND EQUIPMENT

UNDER THE CONTROL OF THE AUTHORITY

This document shall be issued to a Live Line Linesman in charge of the work and shall be
retained by him until the work is completed or stopped.

1.0 ISSUE
1.1 Issued to: ……………………………….. In the employ of
………………………………..
1.2 Work to be carried out:
…………………………………………………………………….

……………………………………………………………………...
1.3 Equipment to be worked on:
………………………………………………………………

……………………………………………………………..
1.4 I declare that all auto-reclose devices:
……………………………………………………
have been switched off and Live Line: ………………………………………………….
Caution Notices have been placed at the following location:
…………………………….
1.5 I declare that it is safe to work to within ……….m of the high voltage conductors as
specified in Table1, Absolute Limits for Qualified Live Line crew, Rule 7.1.
1.6 Special keys or …………………………………………………………
other precautions …………………………………………………………
1.7 No. of circuit identity wristlets issued: ……………………………………………….
1.8 Issued with consent of Controller (Name): ……………………………………………
1.9 Issuing Senior Authorised Person:
Name: …………………………………….. Signature: ………………………………
Time: …………………. Hrs Date: ……………………………………………
148
2.0 RECEIPT

This Section must be signed before work can commence. The Live Line Permit-to-
Work must be retained by the signatory, who must be the Live Line Linesman in charge
of the work, until the work has been completed and Section 4 has been signed. I declare
that I accept responsibility for carrying out work on the apparatus detailed on this Live
Line Permit-to-Work and that no attempt will be made by me or by any person under
my control to carry out work on any other equipment. I shall not leave the site of work
while work is in progress.

Name of person in charge of work………………………….

Signature……………………

Time: ……………………………. hrs Date: ……………………….............

3.0 SUSPENSION / RESUMPTION OF WORK

3.1 I declare that Live Line work on the equipment specified in this Live Line Permit-to-
Work is suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.2 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Live Line Permit-to-Work.

Name of person in charge of work…………………………. Signature

……………………
Time: ……………………………. hrs Date:
……………………….

3.3 I declare that Live Line work on the equipment specified in this Live Permit-to-Work is
suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.4 I declare that I accept responsibility to resume Live Line work on the equipment as
specified I this Live Line Permit-to-Work.
149
 Name of person in charge of work: …………………... Signature: ……………………
Time: ………………………… hrs Date: …………………………….

3.5 I declare that Live Line work on the equipment specified in this Live Lime Permit-to-
Work is suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.6 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Live Line Permit-to-Work.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.7 I declare that Live Line work on the equipment specified in this Live Line Permit-to-
Work is suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.8 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Live Line Permit-to-Work.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.9 1 declare that Live Line on the equipment specified in this Live Line Permit-to-Work is
suspended and all personnel under my control have been withdrawn.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

3.10 I declare that I accept responsibility to resume Live Line work on the equipment as
specified in this Line Permit-to-Work.

Name of person in charge of work: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

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4.0 CLEARANCE

I declare that all persons under my control have been withdrawn and warned that it is
no longer safe to work on the equipment specified in tis Live Line Permit-to-Work, and
that all equipment is clear.

I declare that I have checked in: ………………………………………………………..

circuit identity wristlets.

Name of Live Line Linesman in charge of work: …………………...

……………………
Signature:
…………………………
Time: ………………………… hrs Date:
………………………………

5.0 CANCELLATION

I declare that this Live Line Permit-to-Work has been cancelled with the consent of the
Controller.

Name of Controller: ………………………………………………

Name of Senior Authorized Person: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

6.0 INDIRECT ISSUE

I have read Section 1 of the Live Line Permit-to-Work to:

……………………………… being the Live Line Linesman in charge of the work who
has confirmed that he has made an accurate copy of the Love Line Permit-to-Work and
has signed Section 2.

Name of Senior Authorised Person: …………………... Signature: ……………………

Time: ………………………… hrs Date: …………………………….

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7.0 INDIRECT CLEARANCE

……………………………………………being the Live Line Linesman in charge of

the work has confirmed that he has completed Section 4 of the Live Line Permit-to-
Work Record, and has read it to me.

Signature of Senior Authorised Person:

…………………………………………………..
Time: ………………… hours Date:
………………………………

SAFETY RULES
1. What is the purpose of the Safety Rules? (In your own opinion, what are the
reasons for the safety rules?)
 The rules are intended to promote and ensure a safe, reliable and secure
electricity supply environment for the benefit of the Authority, its stakeholders
who include employed and members of the public.
 The rules protect the Authority’s employees and other people against death or
injury and damage to property and they ensure efficient control, operation and
maintenance of the Authority’s generation, transmission and distribution
systems.

2. Why those that get issued with the safety rules do sign for them and why is the
first page missing in their books?
 When the rules reviewed or revised, each recipient has to be known and be
advised in writing of the revision.
 Signing on page one is an acknowledgment of receipt of the book and it is a
record confirming that one is legally bonded to the rules.
 Indemnity against the Authority in the event of the electrical accident.
 The safety rules are part of the conditions of service.

3. If you violate one of the safety rules as an authorized person what will happen to
you?
 You undergo disciplinary hearing.
 You face criminal prosecution.
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4. Describe the procedure for the revision of a safety rule from where it starts until it
is received by the intended recipient. What action should be taken on receiving
revisions to the safety rules?
 The operator or Senior Authorised person will discover an anomaly or problems
with the application of the safety rule.
 He/ She escalate the issue to the immediate supervision who will discuss with
the SAP until he/she is convinced that the rule must be reviewed.
 The supervisor will take up with the Engineer, or the Manager who if he/she
sees it fit will raise the issue in writing with the EM and the GM.
 After some discussions with the Network manager, EM, etc and the GM is
satisfied that there is a need to revise the rule he/she will put if forward in
writing to the CEO.
 The CEO will set up a committee comprising representatives from generation,
transmission, sub-transmission and distribution to discuss and possibly come
out with the revised rule.
 When the rule has been revised, the CEO will sanction and copies of the revised
safety rule will be sent to each recipient of the safety rule book or the
supplement.
 On receiving the revised rule, each recipient will record at on the Revision page
(i.e. page 9 of the Electrical Safety rules or page 7 of the live line Safety Rules)
and then paste the revised rule over the old one to keep the Safety rule book or
the Supplement up to date.

5. Who can call cause for the variation of the Safety Rules?
 Senior Authorised Person or the operator.

6. Who is the Custodian of the Safety Rules?

 Chief Executive or his authorized representatives.

7. Who is the Chief Executive’s Authorised Representative?

 Anyone acting in his/her capacity.

8. Who can make alterations or variations to the Safety Rules and what is the
procedure? Hs it ever been varies, if so when?
 The Chief Executive or his authorized representatives. As described in Question
3 above, recommendations or suggestions on the rules are made and referred to
the Chief Executive or the representative who will review and revise and all
Safety Rule book holders are advised in writing.
 The minister after reviewing some accident reports.
 Ye, is 1998.

9. Who is the Chief Executive’s appointed representative in (in the context of the
Safety Rules)?
 In Generation – the Power Station Manager.
 In Transmission – the Transmission and Distribution Director.
 In Distribution – the General Manager.

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10. How many Safety Rules books are there in ZESA?
 One

11. Why is the Safety Rules book in grey colour?

 To distinguish between first edition (brown book) and the second edition (grey
book).

12. Who gets issued with the Safety Rule Book? Give examples of the categories of
these people.
 Competent person concerned with the control operation or maintenance of the
Authority’s plant and equipment.
 Examples are engineers, technicians, artisans, apprentices etc.

13. Some groups of people are not issued with the Safety Rules, but must be familiar
with the safety rules. Give examples or categories of people who must be familiar
with the safety rules.
 Loss control officers, security guards, artisan assistants, line workers, technical
auditors, contractor’s representative, crane operators, cable layers.

14. When in doubt as to the interpretations of the rules, whom do you ask for advice
and guidance?
 Immediate supervisor head of department or appropriate senior local official.

15. How do you ensure that Safety Rules are adhered to?
 Carry out spot checks.
 Carry out safety audits.
 Discuss safety rules during Health and safety meetings.

16. What is the most important Safety Rule?

 Every rule is equally important.

17. Which Statutory Instrument does the Safety Rules Fall under?
 The Electricity Act 1985, the Factories and Works Act 1996.

18. For the reliable operation of the Authority’s Power System, what provisions are
there in Electricity Act about the necessary ancillary services?
 Reactive power and voltage control.
 Frequency regulation.
 Operating power reserves.
 Facilities, control and dispatch.

19. What do you understand by “safe supply limits” with reference to voltage and
frequency? What does the Electricity Act provide on quality of supply?
 Safe supply limits are electrical supply tolerances.
 Voltage (+/- 10%) and ZESA improves to +/- 6%.
 Frequency (+/- 2.5%).

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20. To achieve quality of supply, there is need to control the power system voltage.
What are the common methods of voltage control used in ZESA?
 Varying the excitation of generators.
 Adjusting the steam governor speed.
 Opening and closing gate valves using governor at Kariba etc.
 The use of capacitors reactors or static-var compensators.
 Switching in and switching out of lines.
 Tap-changing.
 Under-frequency load shedding.

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  Manual load shedding.
 Ripple relay control (Zelwegger).

21. State some situations for low voltage

 Storms, lines down, excessive loading.

22. What provisions are there in the Electricity Act concerning the safe electrical
environment to the ZESA employees and members of the public?
 Wayleave clearances.
 Safety clearances in substations, across roads and railway lines.

23. Define a Wayleave clearance distance. What are the Wayleave clearances for
different voltage levels?
 Distance across an overhead line symmetrically about the centre line.

Voltage Level (KV) Wayleave Clearance (Metres)

11 10
22 10
33 15
66 30
88 30
132 30
330 60
420 60

24. In which document can information about way-leaves be obtained? What is a way
leave deviance? Give the distance for a 132Kv overhead line.
 The engineering instructions.
 The distance across an overhead line.
 30 metres.

25. Where does ZESA get Wayleave licenses

 Ministry of Local Government or City or Town Council or Individuals

26. Give the Safety Clearanes in substations and across roads and railway lines for
different voltage levels.
Voltage Level (KV) In Substations (m) Across Roads (m) Across Railways (m)
11 2.75 5.8 10.5
22 2.75 5.8 10.5
33 2.75 5.8 10.5
66 3.00 6.0 10.9
88 3.20 6.1 11.1
132 3.50 6.7 11.5

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 220 4.50 7.0 12.4
330 5.50 7.3 13.4
420 5.50 7.3 13.4

27. State the Categories of Authorised Persons

 Competent Person
 Junior Authorised Person
 Senior Authorised Person
 Contractor’s Representative
 Controller

28. Define “competent Person”

 A person over 18 years of age who has sufficient technical knowledge and
experience to safely carry out specific tasks or function.

29. Is a skilled worker, a competent person?

 Yes, provided the person who issues him/her with the job is fully satisfied that
he/she is competent.

30. Define “Contractor’s Representative”

 A competent person, other than a person employed by the Authority who is
required to work on the Authority’s plant and equipment.

31. Who appoints a competent person?

 A Zesa employee is appointed by signing the contract of unemployment and
being issued with the Safety Rule book.
 A contractor’s representative is appointed by signing or receiving a permit –
work or limitation of access document.

32. Can a Contractor’s Representative be issued with the Safety Rules? If No, why?
 No The Safety Rule Book is issued as a condition of service and no contract is
signed between the Authority and the Representative whose personal file is not
even kept by the Authority.

33. Can a non-employee of ZESA receive a Safety document? Give an example of a

non-ZESA employee.
 Yes, as long as that person is competent.
 ZEBRA or VICEMODE contractors.

34. Define items to check on a Contractor’s Representative before issuing a Safety

document.
 Age: Identify if over 18 years by checking the I. Ds, Driver’s License, Passport
etc.
 Technical Knowledge: State the nature of work and explain the procedure
briefly.
 Experience: State the period spent so far in the trade and where else similar
jobs had been done and how long on each job done.

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35. If the Contractor’s Representative is under 18 years of age, what can be done in
order for the work to progress?
 A competent person from ZESA should receive the safety document and the
Contractor’s Representative signs on the declaration.

36. A Contractor’s representative wants to work on a tap changer. How do you

handle him/her? OR If a contractor’s representative is to work in a substation,
what would you do as a SAP? Would you give out copy of Safety Rule Book?
 Determine his/her competency, that is:
- Age: Must be over 18 years old.
- Experience on work to be done and types of tap changers worked on before.
- Safety: Explain the following work arears, danger notices, caution notices,
barricades, PTW (Receipt, clearance, workmen’s declaration), movement of
cranes ladders, use of safety belts etc.
 You give the contractor’s representative copies of the safety rules for a
particular situation.

37. Define “Junior” Authorised Person”. Give a typical example of a Junior

Authorised Person.
 A competent person appointed in writing by the Authority to carry out specific
work on the authority’s Power System in accordance with his/her Certificate of
Authorization.
 Power Station Control room attendant.

38. What are the duties of a Junior Authorised Person or what are Direct Wire Board
Operation?
 Opening and closing circuit breakers, motorized isolation or tap changing from
the Direct Wire Board (Control Room Panel) or Supervisory Control and Data
Acquisition (SCADA).
 Local reading and Auto-Disconnect be regarded as a DWB operation.

39. A Junior Authorised Person is not allowed to perform which operations?

 Operations on the primary equipment that is, switching on the mechanism box,
applying CME.
 Note: A JAP can only perform the above-mentioned operations under the
immediate supervision of a Senior Authorised Person (SAP).

40. Can A JAP carry out a tap changing instruction?

 Only from the control panel or under the immediate supervision of an SAP.

41. What are the limits of a Junior Authorised Person?

 Site and voltage level.

42. Can a JAP apply CME?

 No, unless under immediate supervision of SAP.

43. Define a Senior Authorised Person (SAP)

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  A competent person appointed in writing by the Authority to carry out work and
all forms of switching on the Authority’s Power System in accordance with
his/her Certificate of Authorization.

44. What are the duties or functions of a SAP?

 Those of a Junior Authorised Person.
 Issuing and cancellation of Permit to Work, Live Line Permit-to-Work,
Sanction-for-Test and Limitation of Access documents.
 All forms of switching, issuing and cancellation of SFT, PTW, LLPTW & LOA
documents.

45. What is that SAP can so which JAAP cannot?

 All forms of switching issuing and cancellation of SFT, PTW, LLPTW & LOA
documents.

46. Define a controller?

 A Senior Authorised appointed in writing by the Authority to control power in
one or more of the specific fields of Generation Transmission, Sub-transmission
or Distribution.

47. Give three ways in which a Senior Authorised person can be appointed a
Controller.
 Offer of employment after passing some interviews.
 When section of the network is handed over to the Senior Authorised Person.
 When the Senior Authorised Person has received an AFT document.

48. If you were to be appointed as a Controller, what would be your limits of control?
 The voltage level according to the certificate of Authorisation.

49. What are the duties or functions of a controller?

 Maintains maximum safety personnel, plant and equipment on the Authority’s
power system.
 Approves all operations on the Authority’s plant and equipment.
 Consents to the issues and cancellation of Permit-to-Work, Sanction-for-Test or
Live-line Permit-to-Work documents.

50. How does the controller maintain maximum safety to people and equipment?
 He/she issues instructions to the JAP or SAP. The JAP or SAP reads back the
instructions to the controller and then exercises the instruction after which the
JAP or SAP will confirm the successful operation or execution or instruction to
the controller.

51. How does the controller consent to the issue of the safety documents (PWT, SFT,
LLPTW)?
 By giving the SAP the name of Controller, time or issue and the NCC number.

52. How many controllers exists within the ZESA system and who are they?
 Four controllers (Generation, Transmission, sub-transmission, Distribution).
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53. How many controllers can you have on each piece of equipment.
 One

54. What are the responsibilities of an Authorised Person with regard to taking
equipment out of service for repair or maintenance?

55. What is a Certificate of Authorisation?

 A certificate given to a Competent Person by the Chief Executive or his/her
Authorised Representative confirming that he/she has proved himself/herself
capable of carrying out the duties he/she is expected to perform and defining the
limits of his/he authorization.

56. What do you find on a Certificate of Authorisation?

 Name, Area of Operation, Voltage level.

57. What is contained in a Distribution Controller’s appointment form?

58. Who signs for ) 132Kv switching certificate? And b) 33Kv switching certificate?
(a) Transmission and Distribution Director
(b) General Manager

59. Define “Approved”

 Sanctioned by Chief Executive or his/her Authorised Representative.

60. Define “Dead”

 At or about zero potential with respect to earth and disconnect form any live
system.

61. If you switch off a circuit breaker, can it be said to be dead?

 No, because there is still some charge and at 132 kv can be over 1kv.

62. Define “Live and what voltage would you regard as live?
 Electrically charged.

63. Can you touch insulated cables in substation? Why?

64. Define “Live Enclosure” and give typical examples in your area.
 Any area within generating stations, switching stations or substation in which
live conductors operating at medium voltages or above exist.

65. What low, medium and high voltages?

 Low below 250v, medium 250+ to 650v, high above 650v.

66. How is a live enclosure entry handled?

 The enclosure is fenced or durawalled.
 Gates and doors are locked.
 Anti-climbing devices are used.
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  Danger notices are applied

67. Define “Visitors Live Enclosure Permit”

 A form signed by visitors acknowledge their understanding of the danger of
entering a live enclosure and to indemnify the Authority against injury whilst
they are in or about the live enclosure. The form shall also be signed by a local
Senior Official or Senior Authorised Person.

68. Besides indemnify the Authority against injury that might happen why else does a
visitors sign a Visitor’s Live Enclosure Permit.
 Acknowledgment of their understanding of the danger of entering the live
enclosure.

69. What are Access for visitors or how do visitors access the Authority’s high voltage
plant and equipment?
 The Senior Authorised Person or the Senior Local Official shall explain to the
visitors, the dangers of entering a Live Enclosure and have the visitors sign on
the Visitor’s Live Enclosure Permit.
The following shall be explained to the visitors:
 Indemnity of the Authority against any injury that may happen.
 Limits of approach.
 Anticipated / expected noises or explosions and visitors should not panic.
 Exit routes and ways to the toilets.
 Trenches and how to treat them.
 Handling of ladders and long objects.
 Familiarization with relevant rules.

70. How many visitors are permitted to enter a live enclosure at any time?
 Ten
71. What is the safe distance for visitors from any structure carrying live conductors?
 1m
72. Define Live-line equipment
73. Give examples of live line equipment
 Gloves, link sticks, special spanners, phasing sticks, tong testers etc.
74. What precautions do you take when using ladders and long objects in a substation?
 Ladders shall be of an approved type and of no greater length than is required
for the work involved.
 Ladders and other long objects shall be carried out only under the direct
supervision of a Senior Authorised Person.
 The movement and erection such ladders and objects shall be carried out only
under the direct supervision of a competent person in charge of the work and
when moved at ground level they shall be carried only in the horizontal position
as near ground as possible.
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  All portable ladders within substations or switching stations when not in use,
shall be securely locked to a suitable discharge.
75. What precautions do you take when moving cranes and other equipment into
substations?
 The cranes and other equipment shall be connected to the substation earthing
system immediately as soon as they move into the substation.
76. What causes Step Voltage and how is it protected against?
 Magnetic fields around conductors in a substation will create some voltages on
the ground.
 This is protected against by use of safety shoes, operating equipment whilst
standing on earth mats and also the use of substation stones.
77. What causes touch voltage and how it protected against?
 Magnetic fields around the conductors in substations will create some voltages
on the metal structures and this will differ from any point and earth.
 Use of gloves, link sticks etc will protect against tough voltage effects.
78. What precautions do you take before working on a plan and equipment which can
be
made live from more than one system?
 The authority’s controller shall communicate and agree with the official(s) of
the other system(s) before any switching or earthing is carried or a Permit-to-
work or Sanction-for-test is issued for work on plant or equipment which can be
made live from more than one system.
 The plant and equipment shall be switched off, isolated, earthed and screamed
and released for work by the issue of PTW or SFT documents.
 The switching, earthing, deposits of lock-out-out keys in lock-out-boxes / bars
and details of any Permit-to-work or Sanction-for-Test issued shall be recorded
at the centers concerned.
 Where appropriate copies of the PTW or SFT shall be provided to the official
(s) of the other system (s).
79. What additional precautions do you take when working on a Double Circuit
overhead
line with one circuit live.
 After placing in position a green flag, on the dead side of the tower, and before
any other person is allowed access to the tower, the competent person in charge
at the point work shall climb the tower on the dead side and shall efficiently
connect to earth each individual conductor on that side.
 He/she shall the affix red pennants in the cross-arms supporting the live
conductors at the junction of these cross arms with the tower body.
 The conductors shall remain earthed throughout the progress of the work and
the earths and pennants shall be removed only after all the members of the
working party have descended the tower on completion of the work.
 While affixing or removing the earths and red pennants, the competent person in
charge shall be under observation by another person at ground level.

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80. Define “Earthed”
 Effectively connected to the general mass of earth in such way as to ensure at all
times an immediate discharge of electrical energy without danger.
81. What is the function of the Earthing Grid in the substation?
 To effectively connect someone operating high voltage switchgear to the
general mass of earth.
82. Would you extend the handle of a stiff isolator with a pipe so as to obtain a better
leverage?
 No, because that operation will move someone away from the earthing grid.
83. What are circuit main earths and who applies them?
 Earth connections which are applied on the instructions of the controller before
the issue of a Permit-to-work or Sanction-for-test document.
 CMEs are applied by the Senior Authorised Person.
84. What are additional earths and when /where are they applied?
 Earth connection which are applied after the issue of a Permit-to-work or
Sanction-for-Test document.
 Additional earths are need:
- Where CME are six spans from point of work.
- When there are parallel or crossing lines.
- Where CME is an earth switch used and is in an unconvincing line.
- Where CME is not in visual range.
- Long Ohl where CMEs have been applied at the POL.
85. What are additional earths and when / where are they applied?
 Additional earths should not be more than six spans apart.
86. Can a JAP apply additional earth?
 Yes, because he/she is a competent person.
87. Under what condition can CME and additional earths be applied at the same point?
 When CME is an earth switch.
88. Who issues additional earths and to who?
 Senior Authorised person to a Competent Person.
89. What is the difference between CME and additional earths?
 CME are applied on instructions form the controller before the issue of PTW or
SFT document.
 Additional earths are applied after the issue of a PLW or SFT document.
90. Is applying additional earths switching?
 No, because additional earths are applied without the controller’s instruction by
the competent person and after the issue of PTW or SFT document.
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 91. How can you tell or identify CMEs and additional earths after they have been
applied
at the point of work?

 Read Section 1.6 and 1.10 of the PTW and SFT documents which give details
of where CMEs have been applied and how many additional earths have been
issued.
92. What is the procedure for the use of earthing devices?
 (PFD, discharge and earth).
93. Procedure for connecting portable earths
 Lay the earths in a manner that ensures non-interference with live equipment on
applying them.
 Inspector or check the integrity of the earths (i.e. condition of connections or
joints, conductor signs of damage, functionality of clamps etc).
 Ensure the earth connection is clean and has no signs of corrosion, insulating
staff such as paint.
 Connect the portable earths to the general mass of earth.
 Test for dead by use of voltage tester. Firstly, test on the live conductors/bus
bars and then on the dead busbar and lastly on the live busbars.
 Immediately pick up a link stick or other approved equipment and connect
portable earths to all phases even if works is to be carried out on one phase only.
94. Procedure for disconnecting portable earths:
 When removing earthing devices, they shall be disconnected from the phases
first and the earth system last.
95. How do you ensure its safe to work on a power cable?
96. What precaution do you take in proving for dead? How do you test for dead on HV
equipment?
 The voltage tester must be tested before and after verification.
 Crackle test (use link stick), use of HV indicator shows green-dead, red-live
(neon tester).
97. When can CME earths from point of work and what do you do then?
 Under the terms of the Sanction-for-test document and should be noted on the
exceptions when clearing.
98. CMEs must not be applied within the point of work. Why?
 To avoid or prevent the competent person and the working party from
interfering with the earths as they are not allowed to remove them.
99. What precautions should be taken when a circuit breaker is used as a CME.
 Tripping mechanism to be rendered inoperable and caution notice calling for
non-interference applied.
 Mechanism shall be locked in closed position.
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 100. What are the approved appliances for he earthing of a) power lines b) transformers
101. Would you say that a length of small gauge fuse wire is sufficient to safeguard the
workmen?
102. Why is it necessary to apply a set of portable earths on both sides of the workplace
if an interconnector is to be worked on?
103. What is the purpose of the earthing resistor?
104. Illustrate what is meant by “Common Neutral Earthing” 20,0.
105. In a substation where there is only one transformer installed, would you open the
LV neutral link when you are doing complete isolation of the transformer for
maintenance.
106. What are the dangers of using defective earthing devices.
107. Explain identity wristlets.
108. Is there a difference between CME and portable earth?
 No difference.
109. Define Danger Notice.
 A portable notice in approved form attached to plant or equipment when live,
calling attention to danger of approach to or interference with, the plant or
equipment.
110. Define Caution Notice
 A portable notice in approved form attached to plant or equipment and / or its
control devices conveying a warming against interference and / or its control
devices.
111. Which one of these notices can be used in place of the other when one has run
short of during switching and why.
 The danger notice, because it warns against both interferences with plant or
equipment and the danger of approach.
112. Where would you to Danger Notice and Caution Notice if you were to isolate a
Transformer in a Substation with two transformers operating in parallel?
113. When you have isolated a pole-mounted CB or AR for maintenance purposes,
what approved notice (s) would you apply?
114. Give practical examples where Danger Notices are applied.
115. What is the purpose of the safety Document?
 To define the plant or equipment or area which is safe to work on.
116. What / How many Safety Documents do exist within the Authority. (Five).
 Limitation-of-Access (LOA).
 Live-Line-Permit-to-Work (LLPTW).
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  Permit-to-Work (PTW).
 Sanction-for-Test (SFT).
 Visitor’s Enclosure Permit
117. Define “Limitation-of-Access” document.
 A form of declaration signed and given by a Senior Authorised Person to a
competent person in charge of work in any generating station, switching station
or substation (where a PTW, LLPTW or SFT is not applicable) defining the
limits of the area within which work is to be performed.
118. Is a Limitation-of-Access Document issued to live equipment? Explain and give
example for your answer.
 Yes
119. How is an LOA issued to live equipment?
 The LOA document is stamped LIVE.
120. What Safety document would apply when you want to:
 Paint a cubicle in a substation (LOA).
 Clean contacts of an AVE relay (LOA).
 Replace stolen cross member on 132kv pylon (LOA).
121. Define a Permit-to-Work document.
 A form of document and given by a Senior Authorised Person to a competent
person in charge of work to be carried out on the Authority’s high voltage
equipment for the purpose of making known to that Person exactly what plant
and equipment is dead, isolated from all points of supply and feedback, earthed
and on which it is safe to work.
122. How many PTW documents can be issued on an isolated piece of equipment?
 Only one PTW to an isolated equipment.
123. Is the Competent Person allowed to go and collect an extra drum of oil from the
depot whilst the maintenance of an HV breaker is in progress?
 No, this is prohibited in Section 3 of the PTW.
124. Which three requirements should be met before plant is released to work on a
PTW document?
 Switched off.
 Isolated.
 Earthed and screed.
125. Give steps to be taken when work is stopped and a PTW is still in force.
 Withdraw the working party and tell them work has been stopped.
 Close doors and gates.
 Be the person to leave the point of work.
 Have Permit-to-work in your custody and keep it in a safe place.
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126. Can you suspend a Permit-to-work?
 No
127. What documents can be issued indirectly?
 What documents can be issued indirectly?
128. Explain or outline the procedure for indirect issue of a PTW and give example for
your answer?
 The equipment should be made dead, isolated, locked off, screened and danger
and caution notices posted and be effectively earthed (Rule 14.1).
 The Permit-to-work shall be issued with the consent of the controller.
 If the equipment is interconnected with HV customer or interconnected
substation and requires isolation at these premises, then Section 2 shall first be
signed by the person responsible for the isolation at these premises.
 The Competent Person shall write the details of the Permit-to-Work book and
shall read contents to the Senior Authorised Person.
 The person to whom the PTW is issued should be competent person and all
work shall be carried out under his/her immediate supervision. Situation /
example for indirect issue of PTW.
 You have been doing switching on a line and have isolated the feeder to be
worked on, meanwhile the line gang is waiting at the point of work. On your
way to meet the line gang you find the river is flooded and the line gang is on
the other side.
129. What is Safe Clearance Distance? From what reference point does the safe
clearance distance apply?
 The minimum clearance from the nearest exposed live conductor to ground
level or to any platform or access way.
130. Why are the clearances higher for over railways then over roads?
131. How many people are involved in the in-direct issue of a Permit-to-work
document?
 Conductor
 One or two Senior Authorised Persons
 Competent Person.
132. Can a Permit-to-work be cancelled by the holder?
133. When is one allowed to carry out test on Permit-to-work document and what
precautions would you take?
 If the testing is to be carried out at pressures below 15 V AC.
 Precautions: all cables shall be discharged before and after tests. No other PTW
shall be issued on the plant or equipment other than the PTW under which
testing is to be carried.
134. When carrying out tests on a PTW, who is responsible for testing? Or which
parties or persons will be involved to necessitate the use of the PTN?
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  The Senior Authorised Person.
135. What tests can you carry out at AC pressures below 15 V AV?
136. Rule 17.1 g “…under a circumstance may PTW be inforce on any high voltage
plant or equipment within the points of isolation specified on a Sanction-for-Test”.
Explain whit hi is forbidden.
137. Define “Sanction-for-Test” Document.
 A form of declaration signed and given by a Senior Authorised Person to a
Senior Authorised Person in charge of testing the Authority’s high voltage plant
and equipment for the purpose of making known to that person exactly what
plant is to be tested and the condition under which testing is to be done.
138. Why is it that a Senior Authorised Person issues a Senior Authorised on issuing a
“Sanction-for-test”. If the Protection Test people are not authorized and you want
them to test and transformer, what would you do?
139. Why is not possible to issue a Contractor’s Representative with SFT.
140. SFT makes one be a controller, that is why you can remove CMEs on the line and
same reason why an SFT cannot be issued to JAP. SAP is issued with SFT and the
Protection Technician signs on the declaration.
141. Can a Permit-to-Work and a Sanction-for-test exist at the same time in a
substation? Give reason for your answer.
142. Can you trip test from NCC? What is the procedure for carrying out trip tests on
the Orange Groove – Middle Sabi 132kv feeder?
 No, because trip testing is opening CBS for the relays and there are two
protection relays at NCC.
 The trip tests, involves two Senior Authorised Persons. One will be at Orange
Groove and the other will be Middle Sabi. Firstly, the SAP at Orang Groove
will issue himself/herself an SFT and carry out the trip test whilst NCC will be
observing the alarms and the Middle Sabi SAP will record and observe the
inter-trips. After the tests at Orange Groove, the SAP there will cancel the SFT
and the Middle Sabi SAP will issue himself/herself an SFT and carries out the
tests whilst NCC and Orange Groove SAP are observing.
143. (a) What do you understand by a Workman’s Declaration? What is its use or
purpose?
 A form signed by members of a working party acknowledging their
understanding of the nature of work to be undertaken and the area in which it is
safe to work.
(b) What is the Working Party?
 Person working under the immediate supervision of a Competent Person
(c) What is meant by immediate Supervision?
 The subordinates will be closely monitored.
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144. Is it advisable to sign for workers on the workman’s Declaration form? Can one
sign for the other and under what condition on the Workman’s Declaration form?
 Not advisable at all.
 No one can sign on behalf of another person. This is done if someone is
seriously ill or is dead.
145. What are the differences between various safety documents:
a) Permit-to-work versus Sanction-for-test
(i) Issued to a Competent Person (i) Issued to a Senior Authorised Person
(i) Earth’s cannot be removed before (ii) Earths can be removed before cancellation
cancellation and noted on Exceptions under clearance
(ii) Can be issued and cleared indirectly (iii) Cannot be issued and cleared indirectly
(iii) No provision to note (iv) Provision to not exceptions on clearance.
exceptions on clearance

b) Permit-to-Work versus Live Line Permit-to-Work

(i) No provision for suspension and (i) Provision for suspension and resumption of
resumption of work without work without cancelling
cancelling
(ii) Issued on dead, isolated and earthed (ii) Issued on live plant and equipment
plant and equipment
(iii) Issued to a Competent (iii) Issued to a Live Line Linesman
Person
(iv)PTW indicates the position of CMEs (iv) LLPTW indicates the position of live line
caution notices

c) Permit-to-Work versus Limitation-of-Access

(i) Issued with the consent of the (i) Issued without the consent of the
controller controller who can be notified later.
(ii) CMEs are applied on plant and (ii) CMEs not applied on plant and
equipment under the PTW equipment under the LOA
(iii) Can be issued or cleared (iii) Cannot be issued or cleared indirectly
indirectly

d) Sanction-for-test versus Live Line Permit-to-work

(i) Cannot be issued and cleared (i) Can be issued and cleared indirectly
indirectly
(ii) Issued on dead, isolated and (ii) Issued to live equipment
earthed equipment
(iii) Issued to Senior Authorised (iii) Issued to live line linesman
Person
(iv)Cannot be suspended and resumed (iv) Can be suspended and resumed
without cancelling without cancelling
(v) Indicates position of CMEs (v) Indicates position of LLCN

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 e) Limitations-of-Access versus Live Line Permit-to-work
(i) Issued without reference to the (i) Issued with the consent of the
controller Controller
(ii) Cannot be issued and cleared (ii) Can be issued and cleared indirectly
indirectly
(iii) Issued to a competent (iii) Issued specifically to a Live Line
person Linesman

146. What are the similarities between a Sanction-for-Test and Permit-to-Work

documents?
 Issued and cancelled with the consent of the Controller.
 Issued and cancelled by a Senior Authorised Person.
 Issued and cancelled by a Senior Authorised Person.
 Cannot be suspended and resumed without cancelling.
 Indicate the position of circuit main earths.
147. All Safety documents have some things in common. What are they?
 The controller is involved in all safety documents.
 The Senior Authorised Person is involved in all Safety documents.
148. What safety documents would you apply when you want to?
a) Paint a transformer in a two transformer substation.
b) Paint a cubicle in that same substation in (a).
c) Clean contacts of an A.V.E relay.
d) A linesman to erect a short leg on a 11kv line.
e) Do continuity tests of a 33kv underground cable.
f) Work in a relay room.
g) Replace a stolen cross member on 132 kv pylon.
h) Repair faulty spring charging system on an 11v or 33kv truck type CB.
i) Change tap position of a pole-mounted or ground mounted 11/0,4 kv transformer.
j) Carry out ratio tests on 33/11 kv transformer.
k) Maintain an outdoor 132kv circuit breaker.
l) Carry out secondary injection of relays in the control room.
m) Work on equipment containing SF6 gas.
n) Maintain a withdrawable type circuit breaker.
o) Pressure test a repaired joint on a cable.
p) Show technical auditors a burnt transformer in a substation.
q) Replace broken discs on a live 132kv line.

149. What are the operating rules?

150. Distinguish between operating rules and Safety Rules with regards to the ZESA
Safety Rules Book.
151. State seven switching requirement regarding the operation of Circuit Breakers
and Isolators
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  No switching or associated operations, shall be carried out without the
instruction of the controller except in cases of immediate danger to persons or
plant or equipment.
 When the controller required switching to be carried out, he/she shall
communicate directly with the Junior or Senior Authorised Person who is to
carry out switching. In the absence or failure of direct communication facilities
the message may be relayed by a Competent third party.
 Before any switching or associated operation is carried out on the Authority’s
Power System, which may affect other systems, the Controller shall
communicate with the appropriate officials of the systems concerned and the
routine switching shall be agreed between them. The high voltage switching
shall be recorded at all centres concerned.
 Switching or operations to Controller’s instructions shall be carried out without
undue delay. All switching or operations, whether to the Controller’s
instructions or when there is immediate danger to life, plant or equipment, shall
be reported to the Controller as soon as possible. The circumstances of an
occurrence necessitating emergency switching shall be reported at the same
time, (in time for the SSC to make decisions).
 Should any plant or equipment show signs of faulty operation, the
circumstances shall be reported to the Controller and the plant or equipment
shall be examined before further operation.
 When any person receives instructions regarding work on, or the operation of
plant and equipment he/she shall report any objection to the carrying out of the
instructions to the controller who shall then have the matter investigated and if
necessary, referred to higher authority.
 When the Controller is not in direct /indirect communication with a Senior
Authorised Person, the Controller shall handover control of a section of the
network under his authority to the Senior Authorised Person to perform a
specific task or operation. Control is to be handed back to the controller as soon
as practicable. The control hand-over must be recorded on an approved form.
152. Give or list the types of points of isolation.
 Isolators, links, fuses, rack out CB, Hotline, taps, jumpers, earth switch, Exciter
field switch, solids, valve, auto-recloser, sectionaliser.
153. What is so unique about an isolator or what makes an isolator a better or more
reliable point of isolation that CB?
155. What precaution do you take before you open an isolator?
156. Why is it always preferable to break load or open with a CB?
157. In a CB breaking chamber, the process of are quenching can be either axial or
cross quelling. Explain axial quenching and cross quenching and which method is
more effective.
158. If you were to break an arc, would it distinguish itself more rapidly on a
horizontally positioned D-fuse mount or a vertically positioned D-fuse mount.

171
159. If you were to break an arc on a vertically positions D-fuse mount would you say
that you have a good chance of flashover to earth? If so explain why this is so?
160. When opening a ganged isolating switch would you
a) Open it quickly?
b) Open it slowly?
c) Ease the blades of the isolator open and then open them quickly?
161. When operating a ganged isolating switch, what would you know from the sound
of the arc as the blades part company if:
a) There is a crackle?
b) There are splutters, roars and increases as the blades are parted/
162. When operating a ganged isolating switch, if the arc roars and splutters and
appears to worsen, what would you do?
163. Assuming you have closed an 11kv interconnector which is fed with a Kyle reclose
at each end and you now have the break parallel with D-fuse links. Om opening 1 st
one, there is a small arc, but opening the 2 nd on there is no arc. Describe what
would have happened.
164. Would you expect a workman to carry out maintenance on an isolator to carry out
maintenance on an isolator whose next isolation point is a Kyle Isolator? Why is it
necessary to ensure that there is a visual isolation? Explain.
165. Why are isolators locked open or closed?
 To avoid unauthorized operation.
166. Where would you find a non-standard lock along 11kv lines?
 11 kv isolators used as interconnectors.
167. What is emergency witching and who is allowed to carry it out?
 Opening of CBS, isolator links, hot line taps or other devices in order to avoid
immediate danger to life or danger to plant and equipment.
 Emergency switching is carried out by:
- Any person who is familiar with the operation of the equipment.
- Anyone who understands the danger and knows how to isolate it.
168. (a) Suppose you find a transformer single-phasing because one of its fuses is open
and you close it, would you call that emergence switching?
 No, emergency switching is all about opening and not closing.
(b) Would you carry out any form of “emergence switching” and close some
switch?
 No, but opening a switch in order to remove danger to like or avoid damage of
equipment.
(c) What operations does Emergency Switching permit?

172
 (d) When would Emergency Switching apply?
(e) Having carried Emergency Switching what would your next step be?

169. Can a person not employed by ZESA carry out emergency switching?
 Ye, provided that person is able to identify the danger and knows how to isolate
it.
170. Name 4 Parameters that are a requirement of a complete switching instruction in
their sequential order.
 Time
 Station
 Operation
 Switchgear identity.
171. Name 4 major causes of switching errors.
 Insufficient technical knowledge of plant or equipment.
 Failure to write and read back instruction.
 Failure to correct interpret plant condition.
 Lack of co-odination between control and JAP or SAP.
172. Define competent third party and who appoints him/her?
173. Give examples of categories of people who can be appointed competent third party
and why are they chosen?
174. What is the procedure for conveying or relaying switching instructions through a
competent third party.
175. What switching is a Responsible Person permitted to do?
176. You have find a section of line out for maintenance affecting numerous customers.
On completion of work communication with your Controller is impossible. How
can you restore supply?
177. During switching operations communication with your Controller fails completely,
you find you have two-way contact with another ZESA station which has two-way
contact with your control. Can you utilize this station? If no, what special
precautions must be taken?
178. If power is off in an area and you happen to come across the place and you find an
important function going on, you are approached by the people telling you they
want power what would you do? Suppose all means of communication with the
Controller fails, what would you do?

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ZIMBABWE ELECTRICITY TRANSMISSION COMPANY

LOG LOGO LOGO

Electrical accident handling procedure

Refer to Zesa Electrical Safety Rules No 5.0
This procedure shall be read in conjunction with the Electrical Accident Handling Guidelines.

In case of an accident at the work place, take the following action:

1. Sop work immediately.
2. Withdraw staff to a safe place.
3. Ensure the victim is safe to approach.
4. Render first aid assistance to the injured.
5. Advise the controller who shall also report to his immediate supervisor.
6. Seek medical assistance for the injured.
7. Report the incident to the police.
8. Where possible, protect the accident scene.
9. Comply with NSSA and Factory’s Act by submitting all requisite forms.
10. Investigation of the accident shall be sanctioned by management.
11. Instruction to resume work shall be issued by management through the controller?

Note:
 All accidents including minor and misses are to be reported.
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  All centres to keep accident registers.

ZIMBABWE ELECTRICITY TRANSMISSION AND DISTRIBUTION COMPANY

FAULT REPORT No.: 2602 Form E86(a)
District……………………. Depot Code No: Date: Line construction

Name of Substation Supplying Feeder Feeder REF & Section No:

Type……………
1 Voltage at Fault KV 14 FOR LIGHTING DAMAGED TRANSFORMED ONLY:
2 Time of Interruption HRS Substation Name: Voltage Ration:
3 Time Reported HRS Transformer KVA
4 Time partially restored HRS Lighting Arrester Position: Not Fitted
5 Time fully restored HRS Line Side of isolator Load Side of Isolator
6 Maximum Duration of Interruption HRS D. Fuses Rating (Amps) Solid
15
7 EQUIPMENT OPERATED DESCRIPTION OF FAULTY AND ACTION TAKEN:
Type: Make:
No. Voltage
Rating Rip Setting
Section 8.9.10 refer to Section 7 only
8
No of Reclosing Operation: Available Occurred

9 Recloser Operation: Correct Incorrect N/A

10 Sectionallise Op: Correct incorrect N/A
11 Phases Affected Red Yellow Blue

IF PROTECTED OPERATION INCORRECT GIVE PROTECTION

DETAILS IN SECTIONS 12 and 13
12 OTHER ISOLATING GEAR WHICH OPERATE 16 WEATHER CONDITIONS
Type: Voltage SW No: Fine and Normal Cloudy
Prot Setting & CT Ratio: Hot Rain or Drizzle
13 OTHER ISOLATING GEAR WHICH FAILED TO OPERATE Cold Scattered Lightning
Type: Voltage SW No: Steady wind Severe Lightening
Prot Setting & CT Ratio: High Wind Other – (Specify)
17 SCHEDULE OF DAMAGED EQUIPMENT
Qty Make Type of Equip Serial No. Size Amp Voltage Details of Damage

18 TYPE OF LINE ON WHICH FAULT OCCURED 20 MONETARY OR SUSTAINED INTERRUPTION

33kv 010 22/11kv U.R 016 Monetary 301 Sustained 302

132KV 011 11Kv screened 017 21 DAMAGED MATERIAL (Insert Number X as indicated)

175
 88Kv 012 11kv Underground 018 No of wood Poles 311 Recloser & Seat (x) 318
66KV 013 LV Overhead 019 No. of Arresters 312 Disconnects (x) 319
33Kv Screened 014 LV Underground 020 No. of “T” Formers 313 Cable Box/Joints (x) 320
33kv U.R 015 Service/Meter 021 Conductor (x) 314 U/ Ground Cable (x) 321
19
CAUSE OF FAULT Earthwire (x) 315 Meters 322
Lightning 201 Birds 208 Insulators (x) 316 Cts & VT 323
High Wind 202 Insects/Termites 209 Swgr.OCB’s (x) 317 Other Equipment 324
High Temperature 203 Animals / Reptiles 210 22 TYPE OF SUBSTATION AFFECTED
Rain or Flood 204 Grass Fire 211 For Lightning Damaged Transformers Only

Atmosph. Pollution 205 Corrosion 212 23 Terminal Sub 325 Underline Sub 326
Weathering & Deter 206 Dry rot 213 PROTECTION OPERATION
Trees 207 Unknown 214 Correct 331 Not Applicable 333
Mechanical Failure 261 Electrical Failure 262 Incorrect 332
Inadequate Precautions 271 Vandalism 274 Duration up to Partial No. of consumers
Restoration Affected
Electrical Overload 272 Outside Agency 275 Maximum Duration of No of Consumers
Interruption Affected
Switching Surge 273 Miscellaneous 276
ZESA Power Station 281 Cons Installation 283
Purchased Power 282

OPERATOR NETWORK MANAGER

ZIMBABWE ELECTRICITY SUPPLY AUTHORITY

INTERNAL CORRESPONDENCE

FROM: Area Manager (Northern) AT: Chinhoyi

TO: E Ndlovu AT: Kadoma

DATE: 9 July 1999 REF: 70/5/NB/pm

SUBJECT: DISTRIBUTION CONTROLLER’S APPOINTMENT FORM

In accordance with Section 2.5 of the ZESA Electrical Safety Rules of June 1988, you are
hereby appointed Distribution Controller for the following Areas-:

1. KADOMA 88KV SUBSTATION

(a) Control and operation of the 88kV bus bars, the associated switchgear for the
88/33kV and transformers input bays up to and including the 33kV and the
11kV bus bars and the bus selection Isolators H18 S103, H18 S8 and H18 S29
shall be the responsibility of the Transmission Controller at National Control
Centre.

(b) Auxiliary Supplies

Control of the D-fuses H18 S70 on H18 TA1 and Hi8 S364 on H18 TA2 up to
the LV terminals shall be the responsibility of the Transmission Controller at
National Control Centre.
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 (c) VT Fuses

Control of VT fused is the responsibility of the Transmission Controller at

National Control Centre.

2. Control and operation of the following shall be the responsibility of the Distribution
Controller at Kadoma:

2.1 33kV lines, Substation and Associated 11kV and MV Networks Fed from Kadoma 88
kV Substation.

(a) Golden Valley / Chakari Feeder

From and including Isolator H18 S10 and all the reticulation thereafter up to
including 11kV Isolator H12 S153 but excluding H19 S238, H35 S138 and
sectionalize H12 Si64 and H12 S169.

(b) Unsweswe/Empress Feeder

From and including Isolator H18 S52 and all the reticulation thereafter up to and
including 11kV Autocloser H6 S142 but excluding 33kV autocloser H9 S10 and
its backup and bypass links H9 S9, H9 S11 and H9 S12.

(c) Sanyati Feeder

From and including Isolator H18 S11 and all the reticulation thereafter.

(d) Thistle Etna Feeder

From and including Isolator H18 S9 and all the reticulation thereafter up to and
including 33kV isolator H14 S1 and 11kV isolator H14 S106.

(e) Cam and Motor Feeder

From and including Isolator H18 S30 and all the reticulation thereafter.

(f) Shunt Capacitor Bank

From and including Isolator H18 S69 and the rest of the installation thereafter.

(g) Rimuka Road Feeder

From and including Isolator H18 S56 and all reticulation.

2.2. Chegutu 88kV substation

(a) Chegutu West/Dany Mine 33kV Feeder

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 From and including the normally closed 33kV Isolator H20 S10 and all the
reticulation thereafter.

2.3. 11kV Lines, Substation and Associated MV Networks fed from Kadoma
88kV Substation

(a) Halfway Feeder

From and Isolator H18 S352 and bypass Isolator H18 S355 and all the
reticulation thereafter.

(b) North East Feeder

From and isolator H18 S356 and bypass H18 S359 and all the reticulation
thereafter up to but excluding H35 S138.

(c) Town 2 Feeder

From and Isolator H18 S360 and bypass Isolator H18 S363 and all the
reticulation thereafter.

2.4 Eiffel Flats Rio Tinto 88kV Substation

(a) Control of the 88kV busbars shall be the responsibility of the Transmission
Controller at National Control Centre.

(b) Control and operation of the following shall be the responsibility of the
Distribution Controller at Kadoma:

From and including 88kV hotline taps H33 H1 and H2 and all reticulation
thereafter, including 88/11kV transformers H33 T1 and T2.

2.5. Maranatha 88kV Substation

Control and operation of the following shall be the responsibility of the

Distribution Controller at Kadoma:

(a) From and including 88kV Isolator H33 S3 and all reticulation thereafter.

Note: Paralleling of the Sub transmission Network through 33kV or lower voltage
systems is not permissible.

R.M. NAIK
AREA MANAGER (NORTHERN)

178
Cc : District Manager – Kadoma
: District Manager – Kwekwe
: Chief Systems Controller – NCC
: Senior Customer Services Office - Chegutu

TRANSFORMERS

1. POWER TRANSFORMERS

We have previously considered small transformers, mainly from a theoretical

viewpoint. It is now proposed to examine typical non-portable transformers from a
more practical aspect.

Electrically, transformers function in the manner already outlined. As transformers

become larger, it is of greater importance to minimize the losses. More research and
care during the manufacture of these large power transformers produces efficiencies in
the order of 98%, within normal limits of operation.

1.1 Terminal Markings

Before we consider the various methods of connecting transformer windings let
us examine how the winding terminals can be identified. A system of
designating letters for windings has been adopted as a general practice and can
be found in BS 171: 1970.

The high-voltage winding is identified by a capital letter and the low voltage
winding of the same phase, by the corresponding small letter. A third winding,
if any, is identified by the capital letter appropriate to its phase and is preceded
by the numeral (3). Any additional windings are marked in like manner using
higher numbers in sequence.

Example 1) For a single phase transformer.

A - high-voltage winding

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 a - low-voltage winding

3A - tertiary winding (if applicable)

Example 2) For a three-phase transformer on a common core, or on separate

cores in a common tank.
ABC - high-voltage windings

abc - low-voltage windings

3A 3B 3C - tertiary windings (if applicable)

A subscript is used to identify the end of the winding or point on the winding
where a tapping exists, or where a phase-winding is divided into sections. The
subsequent numbers assigned to the section ends and tappings are arranged so
that one sequence of numbers, beginning with unity, will represent the same
polarity of induced voltage in all such circuits at the same instant.

For tappings on auto-transformers the higher subscript numbers correspond to

higher voltage and the lower numbers to lower voltages.

Typical examples of terminal letters and numerals are sown below. (it is normal
practice to show winding connection diagrams using resistor symbols
(………………………) for the coils).

Example 3) Terminal identification on a single-phase transformer:

A1……………………….A2 - high voltage winding

………………………….. - low-voltage winding
…………………………. - tertiary winding
…………………………. - fourth winding (if applicable)

Example 4) single- phase winding with

tappings at ends.

Example 5) Single-phase winding with

tappings at middle.

2. TRANSFORMER CONSTRUCTION

With the exception of ancillary equipment, a transformer has no moving parts. The
main elements of construction may be categorized, as follows: -

180
 1. Core
2. Windings
3. Terminals
4. Tank

2.1 Transformer Core

Special forms of silicon steel, having low hysteresis loss and high permeability,
are used for the core laminations. It is obtained from the manufactures, coated
on both sides with a very thin layer of heat resisting insulation. The laminations
are punched and miltred by special machines and in many cases sprayed on one
side with a thin coating of “kaolin” to provide further insulation. The core
laminations for large transformers are laid horizontally during construction and
clamped or bolted together before being swung into the vertical position.

Where bolts are used, the holes are carefully spaced to make efficient use of the
minimum number of bolts. Thin “micanite” or “fiberglass” tubes and wood-
sulphate-board washers are used to insulate the bolts from the core.

It is very common practice to fit the laminations to form a multi-step

construction, producing a cross-section having a nearly circular shape. This
ensures the most economical use of copper and core steel.

It is often necessary to build cooling ducts into the core in order to prevent
overheating.

The core limbs are taped with paper or glass fibre before the windings, which
are on formers, are fitted.

2.2. Transformer Windings

The windings are constructed on large tubes, made of paper which is bonded by
synthetic resin. The finished tubes are very tough and impervious to moisture.
The tubes form the core-to-winding insulation.

Strips of wood sulphate board are used as spacers to form oil-ways around
windings and further packings and end-rings are made of ‘permali Board’,
which is formed from wood laminates bonded resin.

Plain copper strip is usually used for winding conductors. Modern practice is to
insulate the copper with paper strip, wrapped helically.

The type of winding used depends upon voltage distribution current carrying
capacity, impedance and weight limitations. Continuous disc or helical are the
two most commonly used types of winding.

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 DISC COILS HELICAL COILS

The low voltage coil is normally wound nearest the core to reduce insulation
problems. The high voltage coil is wound over this, with insulated spacer strips
fitted in between to allow oil circulation between windings.

Disc coils may be wound in sandwitch form with alternate discs being lv and
hv.

2.3 Tertiary Windings

Tertiary, or third, windings may be fitted to transformers for various reasons,

some of which are listed below: -

a. To suppress harmonic voltages.

b. To interconnect three supply systems operating at different voltages.
c. To supply devices, at voltages other than primary or secondary or, with
some different connection, (e.g. delta).

2.5 Transformer Tanks

Small tanks are constructed from welded sheet steel, whilst larger types are
made from boiler plate. A suitable waterproof gasket I fitted at the lid joint.

Conservator tanks are fitted to most oil-filled power transformers to take up the
expansion and contraction of the oil as the temperature changes. This is to
prevent the oil coming into contact with moist air, which would cause
contamination of the oil.

Cooling tubes may be welded onto the sides of the main tank to allow greater
cooling surfaces, and many small fittings, such as lifting eyes, thermometer
pockets, etc, can be included.

3. TAP-CHANGING

Tap-changing is employed as a means of adjusting the secondary voltage by effectively

changing the turns ratio. Adjustment to tappings can be arranged to be carried with the
transformer either ‘off’ or ‘on’ load.

The tapped part of the windings may be at the phase ends, the neutral point, or in the
centre of the phase windings. It is usual to tap the high voltage winding because of
lower current conditions.

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3.1 Off-Circuit Tap-Changing

ELEMENTARY MANUAL TAP-CHANGER

The tappings are taken to some convenient position; either to an oil tight
compartment on the side of the transformer, or to the top of the tank. Re-
connection is made, by either removal connection may be unscrewed or a
suitable switch may be employed. Some switches use the “lead-screw” principle
to traverse the moving contacts.

Off-circuit tap-changing is suitable for seasonal adjustments, i.e. twice per year,
or if a permanent change in load requires adjustment of secondary voltage.

3.2 On-Load Tap-Changing

On modern generator transformers and distribution transformers, connected in

the main transmission grid network, the voltage output must be maintained at a
prescribed value. The reasons for this, and values arrived at, depend upon the
complex nature of an interconnected network, such as the sending and receiving
voltages, and the power factor of the transmitted conditions. A study of these
conditions is well beyond the scope of this text.

However, accepting that a prescribed voltage and power factor can be

maintained by tap-changing whilst on load, then the on-load tap-changer, as an
integral part of the transformer, plays an important role.

3.3 Tap-Changer Operation

The basic function is to change “taps” without interrupting the supply. This
entails making connection to a second tapping, without causing a short circuit
with the existing one, or without causing an open circuit to take place. In either
condition, excessive arcing would take place together with high circulating
currents or large transient currents.

Diagram

183
 REACTOR TYPE TAP-CHANGER

The preceding diagram shows one type of ‘on-load’ tap-changer. Although the
physical position of the taps is in the centre of the winding, electrically in
normal practice to connect them at the earth potential end.

With switch 5 closed, all of the winding is in circuit. If the short-circuiting

switch is closed across the reactor. The current in one half opposes the current
in the other half. No resultant flus occur in the reactor and there is no inductive
volt-drop.

When it is desired to change the tapping position to number 4, the short-

circuiting switch is opened and current flows through only half of the reactor
coil, causing a volt-drop to occur. Switch 4 is closed so that the part of the
winding between tapping points 4 and 5 is now connected through the whole
reactor coil. The reactor will limit the circulating current which will flow
through this loop until switch 5 is opened and the short-circuiting switch is
closed, thus completing the tap-change operation.

A typical tapping range would be 20%, say from +2% to -18% in 16 to 20 steps.

3.4 High-Speed Resistor Tap-Changers

A number of transformer manufacturers favour the High-Speed Resistor Tap-

Changer which, at the present time, is probably the most popular type in general
use throughout the world.

When resistors are used instead of reactors, for transition a large quantity of
energy has to be dissipated. It can be kept to a minimum, only if a very fast
switching sequence is employed. This permits the use of resistors having a
relatively small physical mass.

Two types of switches are employed in the tap-change sequence:

1. Selector switches, which are used to connect the taps to the transformer
terminals.
2. Diverter switched, which divert current through the resistors during
transition.

The latter are designed to withstand making and breaking of relatively large
currents.

The resistors are usually only in circuit for less than 100 milli-seconds and the
heat is quickly dissipated in switch oil. It is essential, that once a tap-change has
been initiated precautions are taken to ensure that the mechanical sequence is
completed, due to the short time rating of the resistors. This is usually achieved
184
 by charging-up a spring system, using an electric motor and at a pre-determined
point, allowing the stored energy to be released. This, together with a series of
“Geneva gears”, provides a positive go/no-go mechanism.

A hand-crank is provided in order that a manual tap-change may be performed,

should motor failure occur.

NOTE
Practical references are based upon a Ferranti Resistor

3.5 Tap –Changer

The sequence of operation involved in a tape-change from tap 1 to tap 2 is as

follows: -

1. Contacts ‘a’ and ‘b’ are closed as shown, and load current is taken
through contact ‘b’, from tap 1: this is the normal running position from
tap 1.

2. The operation of the stored energy mechanism causes the moving

contact stem to commence to travel from one side of the diverter switch
to the other. Contact ‘b’ is opened the load current from tap 1 flows
through the resistor R1 to contact ‘a’.

3. The moving contact continues its travel and contact ‘d’ is closed. Both
resistors R1 and R2 are now connected together from tap 1 and tap 2 and
the load current is taken from the mid-point of these resistors. At this
point, circulating currents will flow in the local loop.

4. Further travel of the moving contact opens contact ‘a’ and the load
current flows from tap 2, through resistor R2 and contact ‘d’.
5. Finally, the moving contact reaches full travel at the other side of the
diverter switch and contact ‘c’ is closed, shorting out resistor R2. The
load current form tap 2 now flows through contact ‘c’ and this is the
normal running position for tap 2.

So far, there has been no movement of the selector switched. Fi a further tap-change to
position 3 is required, the selector switch SI is moved to tap 3 before the diverter switch
operates. The diverter switch then repeats the above sequence, in reverse order.

3.6 Remote Electrical Operation

Diagram

185
 The sequence of operation is initiated from the transformer tap-change control
switches and the motor begins to drive the cam shaft of the timing gear in the
appropriate direction.

During the progression of a tap-change, the appropriate directional switch, and

the maintaining switch are closed, maintaining the supply to the motor and
ensuring completion of the tap change. The sequence switch opens and prevents
any attempted reversal of the motor whilst the tap-change is taking place.

On completion of a tap-change the sequence switch closes and the maintaining

switch opens, interruption the motor supply. This leaves the equipment ready
for the initiation of another tap-change.

The directional switch remains closed in the position occupied during the last
tap change since it is operated from the timing gear cam shaft, through a friction
drive.

3.7 Automatic Control

The tap-change equipment can be arranged to provide fully automatic control of

the output voltage of the transformer. In this arrangement a voltage sensitive
relay is used, together with a time lag relay to prevent the operation of the
equipment as a result of momentary fluctuations in the voltage. Provision is
made for manual electrical control when automatic equipment is fitted.

4. MAINTENANCE OF ON-LOAD TAP-CHANGERS

4.1 Oil

Samples of oil should be taken form diverter switches at regular intervals and
tested to the specification laid down in BS 148.

If the oil fails to meet the electrical requirements, or is discoloured and shows
signs of excess carbon content it should be renewed after the contacts have been
inspected.

186
 4.2 Diverter Switches

Depending upon the type of tap-changer, either lower the tanks or drain the oil
from the chamber. Example insulation, diverter switch contacts, flexible braids
and springs. Remove carbon by syringing clean oil over the components or by
wiping clean with chamois leather.

Most manufacturers recommend that burnt contacts should not be filed or

ground in, but should be used without attention until the end of their useful life.

Old and new contacts should not be used on one switch, otherwise difficulty in
obtaining even contact pressures will be experienced.

Refill with oil and allow to stand for twenty-four hours before making the
circuits ‘live’.

4.3 Selector Switches

Because selector switches are not making or breaking loaded circuits it is

usually sufficient to examine them every two years.

Points to check during inspection are braids, contacts, insulation, spring

pressures and tightness of connection. Check the switch action throughout its
complete range and see that any moving contacts ‘make’ with studs smoothly
without jamming or distortion taking place.

4.4 Lubrication

Grease nipples and oilways may be provided to lubricate the tap-changer and
motor-operating mechanism. Geneva gears require light greasing. The
manufacturer’s lubrication chart should be referred to for full details.

4.5 Auxiliary Switches

The contacts should be cleaned and a smear of contact grease applied to reduce
oxidization.

Any limit switches should be checked for correct operation, ensuring that they
reset correctly afterwards.

6. BUCHHOLZ PROTECTION RELAY

The transformer is a very reliable piece of apparatus but major breakdowns, however
rare, must be guarded against.
187
It is not proposed to deal with the full electrical protection of transformers at this time,
but at this stage the Buchholz Protection Relay is well worth to mention.

6.1. Principle of Operation

The operation of relay depends upon the fact that in oil immersed transformers
every type of fault results in the generation of vapours or gases. It is possible to
detect these faults before any real damage occurs, by means of the relay. under
certain conditions, the alarm given by the Buchholz protector may be the means
of preventing the development of conditions leading to fault, such as the falling
of the oil level due to leaks, or to the ingress of air arising from defects in the oil
circulating system.

The relay is fitted between the top of the transformer tank and the conservator,
in an inclined pipe through which the pockets of gas will rise. Small quantities
of gas, rising towards the conservator, are trapped in the top section of the relay,
which is normally completely filled with the transformer oil, when quantity of
gas reaches a pre-determined level, the displacement of oil caused a float to fall.
The float spindle operates a mercury switch, initiating an alarm.

A second float is situated beneath the first one with a deflector plate in front. If
a large surge in the oil occurs, due to great expansion of gasses, the second float
pivots and operates another mercury switch which causes the transformer to be
stripped out of circuit.
A glass window is fitted to the relay to indicate how much oil has been
displaced. The gas may be seen through this and it is possible to diagnose the
type of fault, by the colour of the gas.

COLOUR CAUSE

White Destroyed Paper

Yellow Damaged Wood
Black or Grey Dissociated Oil

An estimate of the severity and continuance of the fault can be made from the
rate of oil displacement.

6.2 Testing Buchholz Relay

All Buchholz relays should be carefully inspected and tested for correct
operation during the annual transformer inspection. The tests are carried out
with the relay situated in its normal position on the transformer. A portable test
bottle, made of steel, is used to inject compressed air into the relay.

The bottle has a ‘pet-cock’, pressure gauge, relief valve, and Schrader-valve
fitted and can be charged with air from either a compressor, or a foot pump.
188
 After the bottle has been charged to approximately 30lbs/sq in (2.2 kgms/sq
cm), connection is made to the top ‘pet-cock’ on the relay. The pressure is
released into the relay and the air displaces a volume of oil. The level of oil can
be seen to fall by observing the scale reading in the relay ‘window’. When the
float falls, an alarm, usually in a control room, should be initiated.

The relay must have all the air removed after the tests have been carried out.
This is done by removing the test bottle, with all ‘pet-cocks’ on the top of the
relay until oil begins to flow out of it, when it should be wiped clean and the
stopper cap replaced. A final check for oil leaks should than be made.

Diagram

7. SILICA GEL BREATHER

The oil level in a transformer changes as the oil expands or contracts due to temperature
changes. Some form of venting system is required in order to prevent the tank
pressurizing. This creates further problem because air from outside the transformer,
being drawn into the conservator may contain moisture. A silica gel ‘breather’ is fitted
to absorb any moisture from incoming air.

The breather consists of a metal casing in which a container of silica gel is so fitted that
air ‘breathed’ by the transformer passes through it. The sealing gaskets between the
casing and container must be in good condition and correctly positioned to ensure that
the breathing does not by-pass the silica gel.

On the container is a window, which must be aligned with the window of the outer
casing when filling. The silica gel can be seen through the inspection window and is
blue in colour when fully active, but changes colour to light pink when saturated with
moisture. At this latter stage the charge container and carefully sealed off with adhesive
tape to exclude air.

Each breather fitted is chosen to operate effectively over a six months’ period, but this
must be considered very approximate, owing to the fact that the quantity of silica gel
required is dependent upon the quantity of oil in the transformer, the load cycle, and the
atmospheric conditions on site.

The last two conditions are difficult for the transformer manufacturer to assess. It is,
therefore, essential that a regular inspection of the indicator should be made to ensure

189
 safe operation of the transformer. It is suggested that a monthly inspection is desirable
after the first three months in operation.

8. INSULATING OIL TRANSFORMERS

Transformer oil must meet all the requirements of BS 148. It should be tested before it
is put into the transformer and any oil failing the test should be re-conditional before
being used in the transformer.

The equipment recommended for oil treatment should incorporate a filter, heater and
vacuum chamber. All oil handling equipment must be clean and free from moisture
before filling is commenced.

The oil in a transformer tends to deteriorate in service, but this tendency can be greatly
reduced by attention to operating conditions and by treating the oil when this is shown
to be necessary by regular maintenance checks.

The important factors governing the condition of oil are:

(a) Operating Temperature

(b) Atmospheric Conditions

(c) Electric Strength

(d) Presence of Moisture

(e) Acidity

(f) Sludge Precipitation

It is desirable that an oil sampling and testing routine be maintained and a record kept
of operating conditions.

8.1 Operating Temperature and Atmospheric Conditions

When high operating temperatures cause the oil to be maintained at 75 ℃ or

above, sludging develops. Poor substation ventilation, resulting in stagnant or
damp air, may cause condensation or corrosion to occur inside the tank or
conservator. This is liable to promote acidity and sludging.

8.2 Electric Strength and Presence of Moisture

The electric strength of oil is considerably reduced by the presence of moisture

or fibres particularly by a combination of both.

The electric strength test should be carried out by means of the test cell
specified in BS 148. The oil for use in transformers up to the 33kV level should
190
 withstand 40kV for one minute and the temperature at which the test is made
should be measured. On higher operating levels the electric strength should be a
higher prescribed value. The oil fails to withstand the prescribed test voltage for
one minute, and the temperature is outside the limits 15 - 25 ℃, the oil should
be re-tested at a temperature within those limits.

The presence of moisture can be readily detected by the ‘crackle’ test, BS 148.

Failure of either of the above mentioned tests should be taken as an indication

that filtration is required.

8.3 Acidity

Most transformers are free from acidity, but occasionally a unit will develop this
trouble which tends to increase rapidly once it has started. It is frequently
accompanied by a pungent odour or appreciable corrosion under the tank cover.
Regular filtration checks the development of acidity but is not effective in
removing acid once it has formed. To remove acid, the oil may be returned to
the suppliers for re-conditioning or new oil may be provided. In either case the
lower the acidity at the time of changing the oil, the less will be the effect upon
the new oil by acid absorption from the core and windings.

When the oil is removed, the core, coils and tank interior should be thoroughly
washed down with a jet of warm clean oil to remove as much of the old
acidified oil as possible.

8.4 Sludging

In service the oil in a transformer may deposit sludge. It adheres to the core and
windings and tends to choke the oil ducts. This results in higher core and
winding temperatures which causes the formation of still more sludge, the
action being cumulative.

If sludge is present it should be removed by washing all parts with a pressure-jet

of warm clean oil. Sludge generally hardens when it is exposed to atmosphere,
therefore cleaning should be commenced immediately the core and coils have
been removed from the oil.

8.5 Explosive Mixture

Whenever a transformer is opened up, extreme care must be taken to eliminate

any naked flames. This is because oil under normal working conditions may
give off vapour, which when mixed with air results in an explosive mixture.

8.6 Flash – Point of oil

191
 Electrical discharge through oil may result in the flash-point being reduced but
it may increase again after a relatively short time.

When subjected to high temperatures the structure of oil may be changed,

causing the formation of hydrogen and gaseous hydrocarbons. Oil of lower
flash-point is formed under these conditions.

8.7 Method of Sampling Oil

The most minute traces of certain impurities in transformer oil will greatly
affect the electric strength test. It is therefore important that the samples be
handles with extreme care to avoid contamination. Attention is drawn to the
danger of sampling in wet or foggy weather.

Glass sample-containers, preferably fitted with ground glass stoppers, should be

used. Rubber stoppers should not be used.

Cotton waste or other fibrous material should not be used to wipe containers or
apparatus.

Before the actual sample is taken, the entire sampling apparatus and containers
should be rinsed with the oil, which should then be discarded. A small amount
of oil from the tank or package should be allowed to flow over the surfaces of
the apparatus to remove any moisture of dust which may have formed in the
short period before sampling. This oil should be run to …………….

Loose dirt or dust should be removed from tank covers or stoppers before these
are opened.

The method consists of withdrawing and transferring samples of oil from the
bottom of the container (oil drum, transformer tank, carrier or bottle) by means
of sampling-tube or ‘thief’, or by direct tapping when conditions permit. The
tube should be of thick glass, ground slightly oblique at the bottom.

A sampling cag may be used to remove a small quantity of oil from the bottom
of a deep tank or from any level within the tank. It consists of a metal cage,
suitably constructed to hold the appropriate bottle. The combined apparatus
must be of such weight as to sink readily in oil. The cage is suspended on a long
wire or chain and a further chain is used to remove the stopper at the required
level.

Diagram

192
 Immediately after sampling, sample containers should be labelled for
identification and tests.

TYPICAL SAMPLING CAGE

11.2 Caution

Modern oil test-set have safety interlocks built into the hinged chamber covers
in order to prevent accidental contact with the HV circuit. Before commencing
work ensure that the interlock is in working order.

11.3 Preparation
1. Open hinged cover and remove test vessels. Empty residual oil.
2. Examine the condition of the spherical electrodes and if excessive
pitting is observed replace spheres, replace spheres with new ones.
3. Remove any carbon deposits from the spheres, first by using an
approved solvent and then by wiping with a clean chamois leather, or
non-fibrous clothe, soaked in transformer.
4. Check the gap between the vessel electrodes using the 4mm gauge. The
gap should be 4 mm ± 0.02 m.
5. Ensure that test vessels are clean and free from moisture. If necessary,
wipe with a clean chamois leather or non-fibrous cloth soaked in
transformer oil.
6. Examine the oil to be tested and report to the foreman if any of the
following condition are observed:
(a) Cloudy appearance.
(b) Dark yellow colour.
(c) Colour tending towards black.
7. If the oil is found to be satisfactory in appearance, pour a small quantity
over the electrodes. Swill the oil around the test vessel and then our it
away.
8. Repeat operation (7) before the vessel is filled for testing.
9. Ensure that the oil temperature is between 15 and 20 ℃. (Do not
commence tests if this condition is not met).
10. Fill the three test vessels carefully, avoiding splashing, until the oil is at
least 40mm above the electrodes. Leave vessels standing in drip trays for
20 minutes to allow air bubbles to escape. The vessels should be covered
during this period. (Note the order of filling the vessels).

193
 11.4 Tests
1. Select the test vessel filled first and position it between the HV bushings
of the test set.
2. Connect a flexible lead to the HV bushings using the ‘clix’ plugs
supplied with the test set.
3. Close the transparent hinged cover. This operates the HV circuit
interlock.
4. Turn the voltage control knob to zero (full anticlockwise).
5. Switch on mains supply. The neon lamp on the left hand side of the
voltmeter should illuminate.
6. Close the overload switch on the left hand side of the voltage control
knob. The neon lamp on the right hand side of the voltmeter should
illuminate. Check that the overload trips when the cover is raised ½ inch.
Close cover and reset the overload.
7. Raise the voltage to 15kV, then increase at a uniform rate over 10 – 15
seconds to specified value and hold complete breakdown is indicated by
the establishment of a sustained arc as detected by the visual means, or
by the operation of the circuit breaker protecting the test set.
8. Reduce the voltage to zero.
9. Open the overload switch.
10. Open the transparent cover.
11. Remove flexible leads from HV bushings.
12. Remove test vessel.
13. If the oil has broken down before either the specified voltage or
specified time, record these values and repeat the test using the second
sample. In the event of the repeat test also failing, report this to the
foreman, or engineer, who may require that a repeat sample be taken
from the transformer.
14. Position the test vessel filled last (the cell containing oil from the bottom
of the sample bottle) between the HV bushings of the test-set.
15. Repeat operations (2) to (7) (Test procedure).

NOTE The oil should be deemed to meet the requirements of the

Electric Strength Test BS 148, if two out of the three samples
comply with the specified value, provided that one such result
shall be form the bottom of the sample bottle.

16. Repeat operations (8) to (12) (Test procedure).

17. After completion of the tests, deposit any waste oil in the station waste
oil tank and leave the sample vessels inverted to exclude dirt and
moisture.

12 ROUTINE INSPECTION OF METAL ENCLOSED AIR COOLED

TRANSFORMERS

12.1 Equipment

194
 Standard tool kit.
Insulation Tester (of appropriate voltage).
Vacuum cleaning equipment.
Approved cleaning solvent.

12.2 Caution

Obtain any necessary safety documentation and identify the correct transformer
before commencing work.

12.3 Procedure

1. Clean the exterior of the transformer.

2. Remove the top cover of the transformer.
3. Clean the windings and interior using cleaning equipment and approved solvent
as necessary.
4. Examine the windings for damaged insulation.
5. Check fuses and links for continuity, where fitted.
6. Remove the terminal box covers and inspect for cleanliness and tightness of
connections and earth.
7. Replace top cover ensuring that it is dust-proof where necessary.
8. Replace terminal box covers, ensuring a dust-proof compartment.
9. Check that the bolts holding the transformer down are tight.
10. Check that the bolts holding the transformer down are tight.

13. TYPICAL MAINTENANCE ROUTINE FOR OIL FILLED TRANSFORMER

WITH CONSEVATOR

13.1 Equipment

Standard tool kit.

Platform steps or short ladder.
Cleaning cloths.

13.2 Caution

CEGB Safety Rules must be observed throughout this maintenance procedure.

Appropriate safety documents must be obtained. Identify the correct plant to be
worked on.

13.3 Note

This maintenance procedure is for transformers of between 750 and 10,000

kVA ratings, fitted with conservators.

13.4 Procedure

195
 1. Obtain transformer compound key, where applicable, rom Permit-to-
Work Office. (PTW Office). In all cases obtain permission notify the
Assistant Shift Charge Engineer as to which transformer is being
inspected.
2. Inspect the transformer for any oil leaks.
3. Check that spaces between cooling pipes are clear of dust, coal or any
other foreign bodies. Remove any, if necessary.
4. Ensure no debris is resting on the transformer or on the top surfaces of
cable boxes. Remove, if necessary.
5. Check for oil or compound leaks on cable boxes. Record any leakage.
6. Check for external damage to transformer tank and cooling pipes or fins.
Record any damage.
7. Check that the main earthing strap connection is sound and that there are
no signs of corrosion.
8. Check cable cleats in order.
9. Check cables and cable boxes are not overheating.
10. Check cables are undamaged, particularly at ground level.
11. Inspect explosion diaphragm for being intact using torch if necessary.
12. Ensure that the ‘off-circuit’ tap changer hand wheel and drain-valve
hand wheel are padlocked.
13. Check for correct oil level and report to supervisor if topping-up is
required.
14. Inspect Silica Gel breather indicator. Colour of crystals should be blue.
If the crystals are turning pink the charge container requires changing.
Change container if necessary. Check Silica Gel oil seal: level of oil in
small round windows indicates that oil is present.
15. Wipe clean the transformer temperature alarm/indicator glass, taking
care not to disturb the position of the maximum temperature ‘high’
alarm setting.
16. Check that the Buchholz relay has no air showing in the sight glass, and
that there are no oil leaks from the pet-cocks or relay body. DO NOT
VENT THE RELAY UNLESS INSTRUCTED TO DO SO.
17. If necessary, clean out the transformer compound.
18. Check that winding temperature cabinets are secured, if applicable.
19. Return transformer compound key on completion of inspection and
inform the Assistant Shift Charge Engineer that the work is completed.

14 TYPICAL TESTING PROCEDURE FOR BUCHHOLZ RELAYS

14.1 Equipment

Standard tool kit.

Buchholz relay testing bottle.
Foot pump
Multimeter (Avo)

14.2 Caution

196
 Care should be taken when testing the relay terminals as these will be ‘live’.
Before commencing this test, the control room personnel should be requested to
record the initiation of all alarms relative to the transformer under test in
chronological order.

14.3 Test

1. Check that the testing bottle is in working order, that all connections are
tight and that the valves are functioning correctly.
2. Connect the foot pump to the Schrader valve on the test bottle and
pressurize the bottle to approximately 40 lbs/sq inch. Disconnect the foot
pump.
3. Clean the Buchholz relay body and inspection window.
4. Remove the knurled cap from the test cock, which may be on the relay
body, or adjacent to the pet cock, piped from the relay via an adaptor.
5. Connect the testing bottle to the test cock and tighten.
6. Check that the ‘Buchholz links are in position at the relay panel and that
DC supplies are available.
7. Remove the auxiliary terminal box cover. Set the multimeter rand to 250
V DC and clip the leads onto the ‘trip’ terminals (cable ferrules normally
prefixed ‘K’). observe the reading which should be either 110 V DC or
240 V DC.
8. Open the air valve fully on the Buchholz test bottle.
9. Open the test cock fully on the relay body. This allows a sufficient surge
of air into the relay body to trip the relay. When the relay trips the
multimeter reading should fall to zero.
10. Close both the test cock and the air valve on the test bottle and open the
upper pet-cock on the relay body to release air from the relay housing
and pipework. The pet-cock should be closed immediately oi starts to
flow freely out of the cock.
11. The voltage reading should now have re-appeared on the multimeter.

If the voltage reading fails to re-appear, disconnect the multimeter and

test for voltage between each of the ‘trip’ contacts and earth. (Check
meter polarity).

If a voltage present is present between one of the terminals and earth

connect the multimeter to the other (dead) terminal and earth and carry
out step.

NOTE Operation of contacts is now indicated by a voltage reading on the

multimeter.

If no voltage exists between either terminal and earth connect the

multimeter across the contacts and set it to the resistance range, then
carry out step (12).

NOTE Operation of contacts is now indicated by loss of continuity.

197
 12. Using the foot pump, pressurize the test bottle to approximately 30
lbs/sq inch and repeat steps (8 to 11) inclusive with the multimeter
connected as appropriate.
13. Repeat step (12) with successively lower pressures in the test bottle until
the minimum pressure required to operate the Buchholz relay is
determined. Open the upper pet-cock to vent the relay housing after each
test.
14. Transfer the multimeter leads to the Buchholz alarm terminals (after
checking meter range), and observe reading. (Cable ferrules normally
prefixed ‘L’).
15. Pressurize the test bottle to approximately 10lbs/sq inch.
16. Open the air valve on the test bottle.
17. Open the test cock very slowly, allowing air to ‘bleed’ into the relay
housing. Observe the reading on the multimeter and as soon as it falls to
zero note the oil level on the scale in the inspection window, at the same
time closing the test cock valve. Record the level of oil at the time of the
alarm initiation (when the multimeter reading collapsed).
18. Open the pet-cock and release air from the relay housing and associated
pipework.
19. Disconnect the Buchholz test bottle from the test cock and replace the
knurled cap.
20. Disconnect the multimeter leads and replace the auxiliary terminal box
cover.
21. Proceed to the switchgear relay room and check that both the Buchholz
panel relay and the Master Tripping relay have operated.
22. Reset the relays and proceed to the plant room to verify that Buchholz
gas alarm and the ‘PROTECTION OPERATED’ alarm have been
received.

15. TRANSFORMERS AND REACTORS – MAINTENANCE

15.1 Tape-Change Divertors and Mechanism

Maintenance on the divertor switches and mechanism should be carried out at

least once a year and the divertor tank oil changed. Maintenance of the contacts
will depend on their condition and the maintenance of high speed tap-changers
may be extended to two years depending on local conditions.

15.2 Selector Switches

Selector Switches should be examined every five years. For those in the main
tank examination should be when opportunity allows without long outrages or
when the oil is lowered for other purposes.

198
 15.3 Main and Auxiliary Transformers

Insulation resistance of transformer windings should be measured at

commissioning and at least every five years thereafter.

15.4 Transformer Bushings

Condenser bushings should be tested for capacitance or power factor and

insulation resistance every two years. Advantages should always be taken when
bushings are lifted for any reason to test them. (Bushings should not be lifted
only for testing unless their condition is suspect).

15.5 Voltage Transformers

15.5a Electro-magnetic type

Bushing and Oil Tests should be made as for power transformers.

15.5b Capacitor type

(i) Oil in the winding chamber should be tested as for power
transformers.
(ii) Secondary output to be measured at least every six months.

15.5c Haefley Cascade Wound Electro Magnetic Type

The oil level alarm should be checked annually and the oil sampled and
tested every two years in accordance with manufacturer’s instructions.

16. CURRENT TRANSFORMERS – MAINTENANCE

16.1 Oil Filled Gas Sealed Type

The nitrogen deal should be restored at least every two years and the oil
condition checked every five years.

16.2 Oil Filled Oil Sealed Type

The oil should be sampled and tested every five years.

16.3 Oil Filled Un-Sealed Type (Breather)

The oil should be sampled and tested annually.

16.4 Gas Filled Type (SF 6)

The gas pressure should be checked weekly. It is essential that the ambient
temperature has been substantially constant for 2-3 hours when taking readings.
Topping up should be done in accordance with the manufacturer’s handbook.
199
 16.5 Oil Filled Wall Bushings

These should be tested as described in Regional Engineering Memorandum No

12.

16.6 General Transformer Maintenance

Oil samples shall be taken from the main tank and tested as described in
Regional Engineering Memorandum No. 12.

Oil handling and storage shall be in accordance with Regional Memorandum

No. 12.

The conservator should be inspected annually and drained and cleaned at least
every five years.

The cooling motors should be run for a short period each week. At least once a
year the cooler controls and motors should be maintained.

CHAPTER 11
PROTECTION

TIME AND CURRENTGRADING OF PROTECTION – GENERAL

This form protection is most easily applied to radial feeds and consists of two types, i.e.
definite time / definite current, and IDMT or Inverse – definite minimum time. It is also used
as backup protection to “unit protection”, (more on this later).

Just to refresh the student’s memory, a radial network or “dead end feed” as it is sometimes
known as, is a network which is fed at one point (set of busbars) only, i.e. there is no ring feed
or further interconnection with the rest of the upstream network. Thus fault current can only
200
flow in one direction, provided that there are no earthed transformer neutrals or very large
motors on the network.

Time grading: -
The older, traditional fault clearing time allowed between adjacent CB’s was assumed as 0,5
seconds but with improved relays and CB’s this is now accepted as 0,4 seconds.

This is made up of: -

CB tripping and fault current clearance time

(5 cycles with clearance at a current zero) 100 ms
Relay overshoot 50 ms
Allowance for errors (CT and impedance calcs. etc 150 ms
Overall safety margin 100 ms
Overall safety margin 400 ms

Current grading: -
This is as critical as time grading and should invoke the same or progressively higher primary
current settings (relay pickup or start settings) for each successive CB going upstream in the
circuit.

Current settings are not intended to protect the circuit against current overload of any sort but
protect against fault currents only. The minimum setting used is usually twice full load to
prevent operation for loads. Thermal relays are usually used to protect circuits against
excessive loading.

Bear in mind that during a short-circuit, load current virtually disappears with very low
voltages applied to the load, load impedances being usually very nonlinear, especially with
industrial motive power.

Definite Time - Definite Current Relays; -

As with IDMT overcurrent relays, the current setting should be at least twice the full load
current to prevent spurious pickup e.g. when switching in large loads or DOL starting of
motors or even large star-delta start motors.

Grading of protection using Definite Time relays.

Take the case of two transformers feeding 11 kV busbars.

For simplicity, neglect all resistance. For this problem it is simpler to work with ohms instead
of pu. This is because the whole circuit is at the same voltage, i.e. 11kv and the o/h lines are in
ohms.

Diagram

201
For source impedance (132 kV side): -

3
2000∗10
Isc =
√3∗11
= 104975 A at 11kV

11∗10 3
Xsource = = 0,0605 ohms
√3∗104975

For one transformer, rated current = 10 * 10 / √ 3 * 11 = 525 A

12∗11000
Reactance = = 1,45 ohms
100∗ √3∗525

For two transformers, reactance = 1,45 / 2 = 0,275 ohms

Line reactance = 0,5 ohm / km

From BB to A, X = 5 * 0,5 = 2,5 ohms

From A to B X = 10 *0,5 = 5,0 ohms

From B to C X = 20 * 0,5 = 10,0 ohms

From C to D X = 2 * 0,5 = 1,0 ohms

Time setting: -
These should obviously be the minima allowed
Relay C can be instantaneous C t = 0,0 sec
B t = 0,4 sec
A t = 1,2 sec
BB t = 1,2 sec

Current settings
These should take into account the differences in fault currents for one and two transformers
being switched in.

For relay at C, choose C 150 A primary, 3 A on relay

B 200 A primary, 2 A on relay
A 300 A primary, 5 A on relay
BB 500 A primary, 1,25A on relay

202
These greatly increasingly current settings are possible with the large variation in short-circuit
currents.

Also, this is a compromise between maloperation on switching in motors and the very desirable
close protection against excessive load currents, but the setting at C is still low enough to see a
minimum short-circuit current at D.

To cater for the case when one relay fails to clear the fault, at least one relay closer to the
source is set sensitive enough to clear the fault.

The times are plotted as follows: -

Diagram

Instantaneous high-set overcurrent relay elements can be added to advantage, in this case to the
CB at busbars BB. A high-set element set at 3000 A will protect the first section of 2,6km of
line with 2 transformers in circuit or 1,2km of line with one transformer in circuit. This does
not cause incorrect tripping at BB for faults beyond the busbars at A.

The IDMT protection to be dealt with next has the advantage that the time grading is not fixed
by the timer but is a function of the current settings also. Thus, using the same minimum
grading time between adjacent relays of 0,4 seconds, a smaller overall time is the result, giving
faster fault clearance times for close-in faults.

These consist of induction disk relays for most of the older substations, the working principle
of which is shown below. The more recent forms consist of solid state relays with very similar
characteristics.

A brief description of this type of electromechanical relay is as follows: -

Diagram

This consists mainly of two electro-magnets, fixed above and below the disk, the upper electro-
magnet having a winding accepting current (ampere-turns) from the CT via a set of taps on this
winding, connected through a plug bridge. The circuit of the lower electro-magnet carries an
induced current, the flux of which reacts with that of the upper electro-magnet to produce a
driving torque in the disk (against spring restraint), approximately proportional to the ampere-
turns developed in the upper winding.

The disk is designed to close a set of trip contacts at the end of its travel, and the time of travel
of this disk is dependent on its speed and the distance it has to travel or rotate to close the trip
contacts. This distance is set by the adjustable backstop of the disk, the position of this
backstop being calibrated in fractions of the total travel distance (and therefore time) and is
known as the TIME MULTIPLIER (TM).

RELAY C B A BB

203
 CT ratio 50/1 100/1 200/1 400/1
PS 100% 100% 100% 100%
Pri, current setting A 100 200 200 400
S.C. current A 347 1932 766 8080
Fault at C 347 347
PSM 6,94 3,47
Time (TM 1,0) sec 3,5 5,9
Time, sec 0,18 0,58
TM 0,05 0,1
Total CB time, sec 0,58
Fault at B 766 766
PSM 7,66 3,83
Time (TM 1,0), sec 3,4 5,1
TM 0,34 0,77
Total CB time, sec 0,1 0,15
0,74
Fault at A 1932 1932
PSM 9,66 4,83
Time (TM = 1,0), sec 3,0 4,4
Time, sec 0,45 0,88
TM 0,15 0,20
Total CB time, sec 0,85
Fault at BB 8080
PSM 20,2
Time (TM = 1,0), sec 2,3
Time, sec 0,46
TM 0,20
Total CB time, sec 0,86

This whole procedure is easily carried out with all calculations automatically done on a
spreadsheet with Excel for Windows 2000.

This same procedure can be carried out for earth fault currents, to set the current and TM
settings of the earth fault relay elements.

The relay curves for 3-phase faults at C, B, A and BB are plotted on a common diagram as
shown.

Diagram

The closest approach in time of each pair of adjacent curves is allowed to be 0,4 seconds at the
highest fault current affecting the relevant pair of curves.

Again, to reduce the time of relay operation, high-set instantaneous elements can be used,
provided that these high sets are not operated by the short-circuit current at the next station
downstream.

204
A fuse characteristic has been shown which will co-ordinate with the relay protection at C, if
the smallest time difference between the two is equal or greater than 0,4 seconds.

DISTANCE PROTECTION

This form of protection is used for transmission lines and in its usual form is not actually unit
protection per se. it should not be used for lines shorter that about 4km. the relay measures the
ration of the faulted line voltage and the line fault current. It therefore measures the impedance
of the line from the busbars to the point of fault. As such it is also known as “distance /
impedance” protection.

Consider a radial line: -

The relay usually has three elements, whose impedance pick-up points are adjusted to be equal
to about 80% of the line (to the next station in this radial line), known as ZONE 1, to about
120% (i.e. past the next station in this line), ZONE 2, and to about 150% (also past the next
station in this line), ZONE 3.
These distances are known as the REACH of the relay.

Primary Impedance are: -

80
Zone 1 = * 100 * (0,06 + j 0,25) = 4,8 + j 20 = 20,57 ohms
100

120
Zone 1 = * 100 * (0,06 + j 0,25) = 7,2 + j 30 = 30,85 ohms
100

150
Zone 1 = * 100 * (0,06 + j 0,25) = 9,0 + j 37,5 = 38,57 ohms
100

3
primary Z VT ratio
Ratio of the line = = 400∗10 ∗1 = 7,27
secondary Z CT ratio secondary Z

Secondary impedance are: -

Zone 1 = 20,57 / 7,27 = 2.83→ohms

Zone 2 = 30,85/7,27 = 4,25 ohms

Zone 3 = 38,57 / 7,27 = 5,33 ohms

The line characteristic angle is: -

tan−1()x
r
= tan (
−1 0 , 25
0 , 06 )= 76→⸰

205
The relay is set using the above secondary impedances and the angle, with the manufacturer’s
handbook.

Various combinations of Zone 1, 2 and 3 plus carrier communication can be used to

considerably increase the performance of impedance protection.

UNIT PROTECTION
(this is protection to any item of plant, a cable or overhead line).

DIFFERENTIAL PROTECTION:
This is known as Current Differential Protection or Current Balance Protection.

This is the Merz-Price principle, named after the inventor of this system

Diagram

One phase of a 3-phase system.

The CT’s are connected for normal current flow and must be balanced, i.e. identical rations and
matching phase shifts, for the scheme to work.

With the above connection, with no fault (e.g. no earth fault) on the protected unit, CT’s are
connected in opposition and cause current to circulate such that equipotential points occur
across the relay, resulting in no operation of this relay element.

Any fault occurring in this section between the CT’s will result in unbalanced currents being
delivered by the CT’s (i.e. differing in magnitude and phase), which will then operate the relay
element.

GENERATOR AND MOTOR PROTECTION:

Generator and motor (star connection) stators are protected with this principle, whereby in the
unfaulted condition, the current entering a phase is equal to the current leaving the same phase,
both in magnitude and angle.

Generator stator

206
This form of protection can only be applied to a rotating machine stator if “all six ends” are
brought out (i.e. all phase connections are accessible, as shown).

If fault (e.g. earth fault or interphase fault) occurs, the relay will then trip, to disconnect the
item of plant from the system.

The disadvantage of this system is that the relay becomes more sensitive with “through faults”
on a generator and may operate it the CT’s are not perfectly balanced.

Diagram

Application of Current Balance Protection to transformers: -

Transformer

With transformers which are star and delta connected, allowance must be made in the
connections for the main transformer connections and in the CT ratios on the primary and
secondary sides to suit the main transformer voltage ration. This ensures current balance in the
CT’s for no-fault conditions in the main transformer.

Thus the ratios of the CT’s on the primary and secondary sides of the main transformer must be
adjusted for the ratio of this main transformer, so that the same CT secondary currents are fed
to both sides of the relay.

The retraining or bias coils are necessary to overcome the imbalance caused by :-

Magnetizing inrush current on switching in of the transformer.

Tap changing (if used) on the main transformer, would cause unbalance in transformer ratio.
Taps whether automatic or “off-load” cause a maximum deviation in ration of about 15% (-5%
to +10% as boost to secondary volts).

207
RESTRICTED EATH FAULT PROTECTION

This can be applied to the star connection of a generator or transformer and is classed as unit
protection. The application to a transformer is shown below.

Delta-star transformer: -

The star phase CT’s are in the “residual” connection so that any earth fault in the star windings
will cause zero sequence currents to flow between the phase CT’s and the neutral CT.

All CT’s must have the same ratios, for non-operation of the earth fault relay, for a “through”
earth fault (i.e. fault outside the transformer star winding).

Thus, an earth fault within this star winding will produce an imbalance between the zero
sequence currents flowing in the phases and in the neutral, thus causing relaying operation.
This protection is usually arranged to have no time lag.

As already mentioned, this form of protection can be applied to the star windings of rotating
machines, e.g. generators.

PILOT WIRE PROTECTION (e.g. Translay)

This current balance protection applied to cable or overhead line feeders.

Due to the impracticability of comparing the secondary currents of CT’s which are several km
apart, the CT secondary outputs at both ends are converted to a higher voltage (higher
impedance) single phase form and compared via telephone type cable pairs.

Example of the principle of “opposed voltage” on the pilot cable, giving no relay operation for
the no-fault condition.

208
Any fault occurring between the two sets of CT’s will cause imbalance between the phase
summation transformers and pilot current (mA) will flow, causing relay operation (pickup) at
both ends of the feeder.

However, pilot cables laid in the ground are relatively fragile and are exposed to failure (i.e.
open circuit, short circuit or leakage conditions) due to the following: -

Heavy earth fault currents in the ground from the feeder can induce overvoltages and cause
insulation failure in the pilot cable, thus causing protection failure and hence necessitating
frequent testing and repair of this pilot cable. Also, high voltages can appear in the pilot cable
as a result of high fault currents in the line conductors above this pilot cable when applied to
overhead lines.

Pilot cores (very small copper section) become open circuit due to mechanical damage will
render the protection inoperative without any warning to operators. Again, frequent testing is
necessary.

“Solkor” is another similar pilot wire protection scheme but uses circulating currents in the
pilot cable pair, producing zero potential points at the relay coils under healthy feeder
conditions. These zero potential points become non-zero under fault conditions and cause
correct tripping. Automatic pilot monitoring.

Fibre optic combined with transducers are now used to replace the troublesome pilot cables.

Bus bar protection

The bus-zone CT’s overlap the feeder CT’s.

Bus-zone protection can take a variety of configurations to suit the busbars and feeders.

PHASE COMPARISON PROTECTION

For each of the 3 phases, the phase angles at both ends of a transmission line are compared.
Magnitudes are not compared.

Blocks of carrier corresponding to the +ve ½ cycles of this line current are transmitted from
the near end of the line to the far end and are received by the radian frequency receiver at the
far end.

209
Simultaneously, similar blocks of carrier corresponding to the –ve ½ cycles of this line current
are transmitted from the far end and are received by the radio frequency receiver at the near
end.

At both ends, these positive and negative blocks are summed and if they fit exactly to form a
continuous signal at both ends, no tripping is caused, i.e. the line is healthy. But if there is a
phase shift of more than about 10° between the +ve and –ve blocks of carrier, gaps are formed
in the summed signals, casing tripping at both ends of the line, indicating a fault condition on
the line.
Diagram

Health line condition fault condition – discontinuous

continuous carrier received carrier received at both ends.
at both ends tripping occurs when gap exceeds about
10°
or so.

CHAPTER 12

POWER TRANSFORMERS

These are an essential part of any electrical power network, as they transform 3-phase voltages
from one level to another, and eventually transform down to 400 V (240V phase) for use by the
smaller (e.g. domestic) electricity consumer.

The size of power transformers varies from about 10kVA (e.g. single phase supply to a farm
house) to giant 3-phase units rated at about 1000 MVA or more. The voltage ratings of these
larger units goes up to 765kV.

Transformer impedances vary from about 4o/c for small units to about 12o/c for the largest
units.

EQUIVALENT CIRCUIT AND VECTOR DIAGRAM

210
The equivalent circuit (phase to neutral) of the transformer has been covered in Chapter 9 of
this manual. This gives rise to the vector diagram: -

From the equivalent circuit: -

Z of the transformer = { ( Rp + Rs)2 + ( Xp + Xs)2}1/2 ohms

With primary and secondary ohmic values R and X reduced to the same nominal voltage
(either side of the transformer)

Also, Z (ohms) = Z %∗¿¿

Where kV is nominal line voltage.

MAGNETIZING OF THE TRANSFORMER

As can be seen from the vector diagram, the magnetizing current, I M is very small (1 or 2% of
rated primary current).
Where (ɸM / AC is the flux density (Wb / m2) in the core, ɸM flux (wb)

corresponding to peak magnetizing current, and AC is iron core area m2

Also, emf / turn, Et = 4,44fɸM

giving,

Primary volts = 4,44f N2 ɸM

and secondary volts = 4,44f N2 ɸM
where N1 and N2 are primary and secondary turns per phase respectively.

When energizing a transformer, it is a matter of applying an AC supply to an almost pure

inductance (reactance) and the transient currents will depend on the point-on-wave instant of
time that each phase is energized at, since all 3 phases are closed simultaneously in a CB (i.e.
different points on the 3-phase AC waves).

If a phase is switched in at a voltage maximum, i.e. at a current minimum, the initial

magnetizing current is the same as the “steady state” magnetizing current and is small, but if a
phase is switched in at a voltage minimum, i.e. current maximum, the initial transient
magnetizing current can be as much as 50 times the steady state value. This is known as
“magnetizing inrush current”.
Since point-on-wave switching for the energizing of transformers is not usually available, one
or more phases will carry a large magnetizing current transient, containing a large 2 nd harmonic

211
(asymmetric wave) component, which can upset the transformer protection, unless allowance is
made for this. However, for medium voltages (e.g. 11kV, 22kV, and 33kV) using vacuum
switching wit high speed magnetic actuators, point-on-wave switching is possible.

VECTOR GROUPING

Apart from voltage ration, the phase shift between the corresponding primary and secondary
voltages of a transformer depends on the primary and secondary connections.

Some of the most important connections of primary and secondary windings of 3-phase
transformers re tabulated on the next page, with their standard designations and phase shifts.
Diagram

Note that in the case of 180° phase shift, the polarities of the corresponding secondary phases
(relative to primary) are reversed.

Vector grouping, because of the phase shift of the phases is obviously important when
transformers are situated in a network. This, it is essential that there be no intentional phase
shift when a transformer is either paralleled with others or id installed in an interconnection
between parts of a network.

The vector group and therefore the phase shift is always marked on the nameplate of the
transformer. Thus when paralleling a transformer, this information should be checked across an
open CB (with one side of the transformer energized), by means of “phasing sticks” for the
lower voltages and by means of voltage transformers for the higher voltages, before closing
this CB, to finally parallel this transformer. An error in this respect can result in a heavy
circulating current at the least or s “short-circuit current” at worst.

BUCHHOLZ GAS PROTECTION

Inside an oil filled transformer tank, a small arcing fault or a bright hotspot in the iron core
caused by eddy currents will cause a slow release of gas, mainly acetylene due to the
breakdown of oil. This gas will accumulate at the top of the tank and operate the first float in
the Buchholz relay, which will cause the second (surge) float to operate by closing contacts to
trip the CB supplying the transformer and thus disconnect the faulty transformer from the
system.

To transformer tank

212
These oil relays are usually fitted to transformers of about 1000kVA and above, provided they
are not hermetically sealed or nitrogen filled units as many of the smaller transformers are.

CHAPTER 13

INSTRUMENT TRANSFORMERS

VOLTAGE TRANSFORMERS (VT) OR POTENTIAL TRANSFORMERS

These are an essential part of any protection system, being the interface between the primary
quantities being measured and the measuring equipment (e.g. relays).

The purpose of these circuits, these transformers are used mainly for voltage indications,
generator synchronization, voltage regulation of transformers and for impedance relays.

For metering circuits, VT’s are obviously essential for the measurement of power used by
consumers.

For voltages (up to about 66kV) VT’s consist of small electromagnetic transformers (very
similarly to power transformers), with very low ratings (e.g. 150 VA) with core and winding
sizes similar to a 5 kVA power transformer.

As for other transformers, voltage ratio = turns ratio.

Knee point voltage is usually much higher than nominal system voltage to cater for system
overvoltage protection.

Connections: -
VT’s are either single phase units or 3-phase units and the following connections:

Diagram

3 single phase transformers 1 3-phase transformer

5-limb transformer with open delta connection for measuring residual voltage (used for
polarizing directional earth fault relays).

Polarity: -

213
The polarity markings shown are one of the many types used in industry, and are the type
preferred by Eskom.

The meaning is that PI and SI have the same voltage polarity with negligible phase difference.

Loading: -
As mentioned, the maximum load rating or BURDEN as it is known, is only in VA.

The standard secondary voltage output of a VT scheme is 110V. AC for single phase output
and 110 V between phases for a 3-phase system.

Thus, for a star connected output, the terminal voltage of 110 / √ 3 V, or 63,5 V to give 110 V
between phases.

VT load (burden) current causes an internal volt drop resulting in a reduction of output voltage
and a small phase shift. To reduce this effect of the burden and hence improve accuracy, it is
common practice to use double cores and large diameter conductors (low current densities).

A VT have several secondary windings. The protection winding would have a ration error e.g.
3% which is not as accurate as the metering winding. The major difference between these
windings is that the protection winding must provide a relatively accurate voltage for a very
low and very high primary voltages but the metering winding must be very accurate at system
operating voltages (accuracy 1,2%). It is clear that the burden on one winding affects not only
the error on its own dedicated metering would be installed.
The total burden also includes the instrument plus impedance connected to the VT.

CAPACITOR VOLTAGE TRANSFORMERS: -

So far, the VT’s described are of the electromagnetic type, where the iron core and windings
are either immersed in oil inside a steel tank, or encapsulated in epoxy resin.

For the higher voltages as used HV distribution and transmission, the capacitor type of VT is
used for economy, as insulation requirements become very onerous at these higher voltages.

This consist of a low voltage, magnetic VT connected to a capacitor voltage divider as shown
below.

The magnetizing impedance of a magnetic VT is high. A high impedance is required to

minimize pri. current. the sec. leakage impedance consists mainly of resistance. The pri.

214
leakage inductance and in this way reduce the voltage drop due to load (burden). This reduces
measurement errors.

CURRENT TRANSFORMERS

This purpose of these is to transform the primary currents (few amps to many thousands of
amps) to a standard small, measurable current in amps.

Also, CT’s provide the necessary isolation form high voltages on the primary circuits. CT’s
should maintain an acceptable ratio between primary and secondary currents in the protection
circuits, with negligible phase shift. For CT’s the current ratio is the inverse of the turns ratio.

The standard secondary currents are 5 A and 1 A being favoured today, because of the greater
distances over cables that the secondary current must be sent.

Connections: -

Circuits for CT’s for various protection schemes are on page 68 and other pages.

Polarity: -
Most CT’s above 50 to 100 A rating are of the bar type with the primary conductor passing
through the hole in the toroid type iron cored winding of the secondary coil as shown.

Bar type CT (high ratios)

Equivalent circuit of CT: -

The above equivalent circuit gives the following diagram:

The magnetizing current, 1M is controlled by the magnetizing force, h (ampere-turn / m units)

required to give the necessary flux (φ), to maintain the secondary induced voltage Vs , and
hence the terminal voltage Vs, in order to supply the burden with current 1s.

CT errors: -

These are given as

215
 (1 s−1 p ') 1e
Current ration error (%) = * 100 = * Cos (ɸB - ɸS) * 100
1 p' 1 p

1e 180
Phase angle error, ɵ = * Sin (ɸo - ɸS) * degrees.
1p π

These errors have more significance for power metering circuits.

For metering circuits an error of only a fraction of 1% or 2% is allowed but for protection
circuits, several 1%, e.g. 10% may be allowed.

Magnetizing curve

For protection purposes, CT’s have a knee point on the curve allowing for fault currents up to
about 20times full load, i.e. for an “accuracy limit factor” (ALF) of 20.

The knee point is defined as the point on the magnetizing curve at which a 50% increase in
mmf (ampere-turns) only produces a 10% increase in flux, i.e. secondary voltage. Beyond this
point, severe saturation of the iron occurs.

The burden on a CT is again the VA rating at full load of all instrument load plus lead (cable)
VA and should not exceed the burden rating of the CT (e.g 5,10 or 15 VA), to allow for a
reasonably close ration (e.g within 10%) to be preserved at about 20 times full load, for faults.
Thus the total burden impedance appearing across the secondary terminals of the CT must be
limited.

CHAPTER 14

OVERVOLTAGE PROTECTION

Basic Insulation Level (BIL)

This is the impulse withstand (phase to earth) of any electrical equipment, using a standard
1,5 /50 μs or 1,2 /60 μs impulse wave and is the level beyond which breakdown may occur on
application of this impulse. A margin of safety is usually allowed for. Other impulse wave
shapes are also used to simulate lighting, etc.

BIL is either expressed in kV or pu where: -

216
 Crest value of impulse wave
BIL = pu
√2∗operating voltage (phase ¿neutral )

Impulse Ratio: -

This is the ration of crest value of impulse wave (to just cause breakdown), to the peak value of
working voltage (same as BIL in pu).

For example, the system must withstand switching surges with commonly occur between 2 and
4 pu (based on peak to earth operating voltage).

Overvoltage: -

These arise from the following: -

1. Steady state overvoltages.

These arise from system conditions lasting from a few seconds to many hours. Primary
plant is designed to permit a maximum voltage for 2 seconds (e.g. V MAX = 300kV for
88Kv nominal).

2. Transient overvoltages.
These arise from lightning surges (direct strikes or induced) and switching surges such
as breaking of currents e.g. fault currents, or making of currents e.g. emerging of
capacitor networks in installations.

Insulation co-ordination: -

It is not economical to design insulation (i.e. phase clearance on overhead lines or insulation
thickness in transformers, cables, etc.) to withstand surges due to lightning.

In the case of overhead lines, flashover occurs across the insulators and reliance is placed on
tripping and auto-reclosing to extinguish the arc and re-establish supply. With all busbars and
all equipment with solid or liquid insulation, flashover or internal breakdown must be
prevented by means of sure diverters or lightning arresters (previously described), connected
between each phase and earth.

These diverters have traditionally consisted of a precision spark gap in series with a valve
block (block on non-linear resistance material) but more recently replaced by a block of very
non-linear resistance material) but more recently replaced by a bock of very non-linear
resistance material (ZnO) which passes the surge with a low resistance and reverts to its normal
very high resistance when working voltage is re-established. The gap is unnecessary with this
type.

For systems with working voltages up to about 400Kv, lightning is the usual cause faults, but
above this, switching surges with much longer rise times control thee design. Switching surges
have longer duration and hence could cause breakdown at somewhat lower crest voltages.

217
For overhead lines, which are not normally fitted with surge diverters, except at their
terminations, the economic withstand level is defined by some utilities as to give a flashover
probability of about 1,1% based say on a switching impulse level of 2,7 pu (impulse ratio).

In the case of substation equipment this probability should be nil, with the protection of surge
diverters correctly applied. However, minimum spark over voltage must be above peak
working voltage to avoid premature operation.

A 15% margin or greater is allowed for this. Failure of correctly protected equipment is always
due to the intervention of some cause such as vermin (birds or rats), vegetation blowing in or
water leakage onto equipment. Water in transformer oil is a common cause of a faults.

A large margin should be allowed between the maximum arrester breakdown voltage and
equipment withstand, which latter is either the IL or a high percentage of it. Withstand voltage
of equipment ˃ arrester breakdown voltage.

Diagram

Example of insulation co-ordination in a HV substation

a) Characteristic of lightning arrester.

b) Line insulation.
c) Transformer insulation.
d) Busbar insulation.

Impulse levels and clearances in air, as has been recommended in the past.

System System Clearances Impulse

nominal max. Indoor Outdoor level
voltage kV Voltage kV
rms kV rms
11 12 152 152 205 280 153
22 24 230 255 305 405 209
33 36 305 380 430 585 278
44 48 380 485 535 735 348
66 72 560 710 740 1040 487
88 100 710 940 990 1370 625
132 145 1040 1400 1450 1980 905
275 300
400 420
765 800

Switching surges

218
These are mainly due to the interruption of short-circuit currents and are considered interrupted
at the natural current zero (+ve or –ve ½ cycle). The case of current chopping will not be
considered here as this is usually not allowed to happen on HV circuits, except in the case of
high speed fuses.

For a brief look at the theory of switching surges, consider a fault along a simple transmission
line, the equivalent of which is shown below.

C is the capacitance across the switch contacts (very small)

Since the fault current is suddenly reduced to a continuous zero value after the circuit breaker
has opened, a ramp current (equal to the theoretical missing fault current after t=0) is produced
due to the inductance with capacitance shorted by the fault which feeds into C and causes the
high frequency (ringing transient voltage, v1).

Where VMAX = recovery voltage + surge voltage

= EMAX + V1

= √2 . E ¿ = √2 . E ¿
NB. The polarity of the above diagram can be reversed 9inverted) for breaking the –ve ½
cycle current, but giving the same maximum voltage magnitude.

Thus a peak voltage of 2.√ 2 E appears across the opening CB contacts and must not cause a
restrike across these contacts.

This high frequency component of voltage is transient due to the log decrement caused by
the ever-present circuit resistance, although small.
219
CHAPTER 15

EARTHS AND EARTHING

Apart from the method of connection of the star point of a star winding or NEC to the
station earth, the station earth itself is of great importance to protection.
The object is to obtain the lowest resistance with the most economical arrangement.

Resistance of an earth: -

The actual resistance of an earth electrode is its resistance to the earth mass as a whole, i.e.
to ꝏ and depends on the type or configuration of this electrode and the earth
resistivity, ρ in ohms-m.

Concept of earth resistivity; -

The resistivity of the material forming the cube

= R m2 / m or Rv-m2-m-1 or R-m ohm-rm units,

where R is the resistance in ohms measured between the two opposite faces of the cube.

Typical earth resistivities: -

Loams, garden soil, etc 5 → 50 ohm-m

Clay 8 → 50
Clay, sand and gravel mixed 40 → 250
Sand and gravel 60 → 300
Slates, shale, sandstone, etc 100 → 500
Crystalline rock 200 → 1000

These figures are for the average moisture content of the ground, which can vary greatly
depending on depth of the earth electrode and season of the year.

TYPICAL POWER LINE CARRIER LINK

220
Figure 1

POWER LINE CARRIER TERMINAL EQUIPMENT

221
Figure 2

AMLITUDE MODULATION

222
Figure 3

223
LINE MATCHING EQUIPMENT

Figure 4

EQUIPMENT INTALLATION

224
Figure 5

COUPLING CAPACITOR WITH INTEGRAL LINE TRAP

225
Figure 6

CAPACITOR VOLTAGE TRANSFORMER

226
Figure 7

PHYSICAL POSITION OF COUPLING EQUIPMENT

227
Figure 8

PHYSICAL POSITION OF COUPLING EQUIPMENT IN HV YARD

228
Figure 9

LINE TRAP

229
Figure 10

PLC COUPLING ARRANGINGMENTS

230
Figure 11

231
 Transformer protection

ALSTOM

Transformer Fault Categories Alstom

1. Winding and terminal faults

2. Sustained or uncleared external faults

3. Abnormal operating conditions such as overload, overvoltage and

overfluxing

4. Core faults

232
Transformer Protection (1) ALSTOM

Transformer Connections
Overcurrent Protection
Directional Protection of Parallel Transformers
Partial differential Protection of Parallel Transformers
Earth Faults on Transformer Windings
Unrestricted Earth Fault Protection
Restricted Earth Fault Protection
Biased Differential Protection of 2 and 3 Winding Transformers

Transformer Protection (2) ALSTOM

Combined Differential and Restricted Earth Fault Protection

Protection of Auto – Transformers
Inter-Turn Faults and Buchholz Protection
Overfluxing Protection
Overload Protection
Transformer Feeder Protection

233
 Transformer protection

ALSTOM

Transformer Protection (3) Alstom

234
Transformer Protection (4) ALSTOM

Transformer Protection (5) ALSTOM

235
Transformer Connections ALSTOM

Transformer Vector Groups ALSTOM

Group 1 Yy0
0° Phase displacement Dd0
Zd0
Group 2 Yy6
180° Phase dispalcement Dd6
Dz6
Group 3 Yd1
30° Lag Phase displacement Dy1
Yz1
Group 4 Yd11
30° Lead phase displacement Dy11
Yz11

Transformer Connections ALSTOM

236
 - “clock Face” numbers refer to position of low voltage phase-neutral vector
with respect to high voltage phase neutral vector.
- Line connections made to highest numbered winding terminal available.
- Line phase designation is same as winding.
Example 1 : Dy 11 Transformer

Question : how to connect windings

Dy 11 ALSTOM

ALSTOM

237
1. Draw Phase-Neutral Voltage Vectors

ALSTOM

2. Draw Delta Connection

ALSTOM

238
3. Draw A Phase Windings

ALSTOM

4. Complete Connection (a)

ALSTOM

239
4. Complete Connections (b)

11kV Distribution Transformers ALSTOM

Typical Fuse Ratings

Transformer rating Fuse

kVA Full load Rated Operating
current A Current time at 3 x
(A) rating(s)

100 525 16 3.0

200 10.5 25 3.0

300 15.8 36 10.0

500 26.2 50 20.0

1000 52.5 90 30.0

240
Typical Small Use of Instantaneous Overcurrent Protection
Protection

Typical Medium Transient Overreach

Protection
Concerns relays response to offset waveforms
(DC transient)

241
 Use of Instantaneous Overcurrent Protection ALTOM

Transient Overreach ALSTOM

Concerns relay response to offset waveforms (DC transient)

242
 Overcurrent Relay Sensitivity to ALSTOM
Earth Faults (1)

Overcurrent Relay Sensitivity ALSTOM

To Earth Faults (2)

243
 Overcurrent Relay Sensitivity to ALSTOM
Earth Faults (3)

Earth Fault on Transformer ALSTOM

Winding

244
ALSTOM

245
ALSTOM

246
ALSTOM

247
ALSTOM

248
ALSTOM

249
ALSTOM

250
ALSTOM

251
ALSTOM

252
ALSTOM

253
ALSTOM

254
ALSTOM

255
ALSTOM

256
ALSTOM

257
ALSTOM

258
ALSTOM

259
ALSTOM

260
ALSTOM

261
ALSTOM

262
ALSTOM

263
ALSTOM

264
ALSTOM

265
ALSTOM

266
ALSTOM

267
ALSTOM

268
ALSTOM

269
ALSTOM

270
ALSTOM

271
ALSTOM

272
ALSTOM

273
ALSTOM

274
ALSTOM

275
ALSTOM

276
ALSTOM

277
ALSTOM

278
ALSTOM

279
 ALSTOM

DIFFERENTIAL PROTECTION
280
This is a form of protection which operates, usually instantaneously, for faults in a given zone.
It does not operate for faults outside this zone.

1. BEF. Probably the most common form of differential protection on the ESC system.
See fig 1.

Basically it is a form of current balance where for Earth faults outside the zone or for
Phase Faults current in the C.T.’s, perfect balance is maintained and no current flows in
the relay. For Earth faults inside the zone any unbalanced current flows through the
relay.

The most important part of the protection is the C.T.’s and they can cause spurious
operation. Even if C.T.’s are perfectly matched their outputs can differ under fault
conditions and the approach is to take the worst case, i.e. one C.T is fully saturated and
another is producing full output.

The saturated C.T. produces no current and is represented by its winding resistance
only; this is much lower than the relay resistance so the full output of the healthy C.T,
is considered to go through it. There will be a voltage developed across the saturated
C.T. which is also across the relay and this voltage must be less than the voltage setting
of the relay.

The voltage setting is also selected so that the relay is as sensitive as possible for faults
in the protected zone. This is done so that as large a portion of the winding as possible
is protected.

Calculate the fault setting of the relay as follows: -

1) At the selected voltage obtain Mag. Current for all 4 C.T.’s.

2) Ass the total of these to the required relay operating current.

3) Allowing for errors caused by phase angle this is the total secondary current
required. Multiply by C.T. ration to obtain current.

There are basically three schemes in use on the ESC system: -

a) The payrolls system using 2B3 or 4B3 relays with an operating current of 20m A
and an internal adjustable resistor. The setting is calibrated in Volts.

b) The older Payrolls system with an R.S.G. relay having an adjustable operating
current usually about 40mA- and an external resistance.

c) The CAG type of relay with a plug bridge giving adjustable current settings of
0,1A upwards and an external adjustable resistance.

Scheme a) is usually the best because it is simple, sensitive and stable. For the other
two the calculations are carried out in the same way and the voltage setting arrived at
281
 considering operating current and resistance value. The sensitivity of the relay is, then
checked as above.

2. TRANSFORMER BIASED DIFFERENTIAL PROTECTION

This is a circulating current scheme in which H.V. and L.V. currents are compared; at
balance there is very little current in the relay. However, there are numerous difficulties
associated with this type of transformer protection:

a) The windings on H.V. and L.V. sides can be connected differently e.g. star-
delta.

b) The H.V. and L.V. currents is differ according to the inverse of the voltage ratio
and where different tap positions are available different current ratios will
result.

c) When energizing a transformer magnetizing inrush current occurs and this is

only present in one winding.

The solutions to these problems are: -

a) For different Primary winding connection, the C.T. secondary circuits can be
connected to compensate for phase shift. See fig. 2 for a typical example. There
are many ways of doing this and it becomes a bit more complicated if it is
necessary to incorporate BEF protection in the circuit.

b) For slight differences in current it is usual to compensate using a restraining

winding. For heavy through faults it is possible to get sufficient current to
operate the relays; however, the increased bias current raises the operating point
and by correct selection of the bias tapping maloperation can be prevented.

c) For magnetizing surges in older relays it used to be necessary to increase the

time setting. An example of this is the JJA relays at Umniati. However, with the
Duobias relays a second harmonic of the current, which is present during
switching surges but is very small during faults, is filtered out and used.

Biased differential protection for generators is generally very similar except it is

unnecessary to allow for harmonic bias.

The protection can be used for three winding transformers or for generators with unit
transformers with slight modifications.

3. PILOT WIRE PROTECTION

This is a form of differential protection used on feeders where it is necessary to have

relays at both ends of the feeder. Special features of this protection are:

1) The smallest possible number of pilot wires should be used (2).

2) Tripping should occur at both ends for a fault fed from either end.
282
 3) C.T. requirements should not be too stringent as perfect matches are not always
possible.
4) Pilot wire requirements with regard to capacitance and resistance should not be
too stringent.

There are two basic forms, balanced voltage and circulating current, both of which are
present on the ESC system. Solkor A.B and C are variations of the balanced voltage
scheme and Solkor B is a circulating current scheme. One feature that is common to
both and produces a single output for a three-phase input is the summation transformer.

Summation Transformer; the primary is a tapped winding with four connections

brought out. See fig. (3). The table shows the output that is obtained for various fault
condition, illustrating that it is most sensitive for earth faults.

Other important functions of the summation transformer are to isolate the C. T’s from
the pilot wires, allowing earthing of C.T’s and to match the impedance of the pilot wire
circuit to the C.T’s by having a large number of secondary turns.

SOLKOR A. This was the first Solkor scheme to be brought out, the basic circ as
shown in fig. 4. Under load or through fault conditions the voltages in the pilots balance
and no current circulates through the operating coils.

Difficulties are: -

1) Because there is no current in the pilots somewhere saturation of C.T’s must

occur. The summation C.T.’s are arranged to saturate before the main C.T. and
these are perfectly balanced i.e. there is current in the primary of the summation
C.T. but not in the secondary.
2) The C.T.’s must be of a high knee-point to prevent premature saturation. The
50 If
knee-point voltage is given by the manufacturers as greater than + (Rc.t.
1 N
+ 2 RI) where I= the relay rating, if – maximum primary fault current, N = C.T.
ratio, Rc.t = secondary resistance of C.T.’s and R1 = secondary lead resistance.
3) Because of the voltage on the pilot wires capacitive currents do follow and can
become a problem over long distances, though the restraining coils help to
maintain stability.
4) The turning capacitors are included to filter out high frequency currents caused
by distortion in the circuits, they help to increase stability but I have found thy
are a weak point in the circuit and frequently develop faults.
5) High voltages can be present on the pilots.

Solkor B and Solkor C are theoretically identical but components and arrangements
have been changed.

COMMISSIONING; When commissioning the following must be checked: -

1) The condition of the pilots.

2) The quality of the C. T’s.
283
 3) The correctness of the C.T. connections.
4) The correct operation of the relay.
5) The stability of the protection under through faults.
6) The tripping circuit.

SOLKOR B. This is a circulating current scheme as shown in fig 5. The only

difference between this and the generator or transformer differential protection is that
there is relay at both ends of the feeder and that pilot wire, are used for the current to
circulate. Because of this an artificial electrical mid-point has been created and during
each half-cycle this mid-point is across one of the relays, the other relay having a diode
in series to prevent operation.

During an internal fault, whether fed from one end or two the balance is disturbed and
current will flow through the operating coils. The voltage distribution is shown in fig. 5
for one half cycle.

Note that the scheme is dependent upon the pilot resistance being approximately equal
to the resistance in the relay; an adjustable pilot padding resistor is provided to ensure
this.

Generally speaking, this is superior to Solkor A, B or C in every way: -

1) No saturation of C.T’s or Summation transformers except under heavy through

faults and then the effects are not so serious.
2) Capacitive currents are no problem.
3) Voltages induced on the pilots are not so high.
4) Pilot wire supervision can be arranged.

COMMISSIONING.When commissioning the following points must be checked in

addition to the points mentioned for Solkor A.

1) The pilot wire resistance must be measured and the padding resistors adjusted.
2) The pilot wire polarity as well as the polarity of the C. T’s must be checked.
3) There is test link in series with the relay operating coil – this MUST be
connected.

NON-UNIT FEEDER PROTECTION

Non-unit feeder protection may be divided into three main sections.

Section A - Non-directional time and current-graded systems for the protection of radial
feeders.

Section B - Time and current graded systems to which a directional feature has been
added, for the protection of feeders which are to operate in parallel, or which
form part of a ring main or inter-connected power system.

284
Section C - Distance protection schemes whose characteristics overcome some of the
limitations of time and current graded systems, which are now widely used on
transmission and distribution feeders.

System A and B are used in places where time-lag for fault clearance would not cause system
instability or cause excessive damage to the healthy plant cables or lines. In addition, these
systems are used as back-up to high speed protection on higher voltage systems. However, on
275 and 400kV transmission lines “Distance” is very often used a back-up instead of time
graded systems.

Note: Unit feeder protection involves pilot wire, carrier or radio information channels such as
in SOLKOR, TRANSLAY, PHASE COMPARISON etc, and will not be dealt with in this
paper.

A. NON- DIRECTIONAL TIME AND CURRENT-GRADED SYSTEMS

Grading may be achieved in one of the following ways: -

(i) By using time grading.
(ii) By using current grading. (Inst.)
(iii) By use of combination of current and time-grading;
a) By employing time-limit fuses in parallel with direct acting trip coils.
b) By employing inverse definite minimum time relays (IMT).

The Commission allows 0,4 seconds time interval for discrimination between successive
current / time graded systems.

B. DIRECTIONAL TIME AND CURRENT-GRADED SCHEMES

A directional feature becomes necessary when it is possible to feed into the fault from
both ends of the line, this may occur for the circuits shown in Figure 1.

It will be seen from the arrows marked on the diagrams to indicate direction of current
for relay pick up only when the current flows away from the bus bars. The time/current
grading principles identical to those in section A.

285
ABB POWERLINE CARRIER TRANSMISSION

MODULAR COUPLING DEVICES

MCD 80

286
GENERAL

Asea Brown Boveri power line carrier links FEATURES

from the information transmission
backbone of many energy supply  High degree of modularity
authorities throughout the world. The Compact unit with variable
system, known as PLC for short, has been modules.
of considerable value in network control
over the years, since it presents an  Maximum personnel protection
economical solution to many information Insulated enclosures as well as
transmission problems. Among the signals design measures minimize electrical
which can be transmitted safely and hazards.
reliability by means of PLC are speech,
data for energy management, line and  Programmable
object protection with new systems coming High-pass version permits field
into operation, and existing networks being matching to any coupling
continually extended. It has become parameters.
increasingly important that PLC equipment
be compatible and of modular design.  Weather and climate proof
Absolutely corrosion proof owing to
The modular coupling devices MCD 80, as poly-glass equipment housing.
introduced herewith, which form the
interface between high tension gear and  High transmission power
PLC equipment, fulfill above requirements handling
to an utmost extent. Up to 1000 W PEP

 Economical
Optimus utilization of coupling
capacitance, facilitated stocking of
spares.

Fig 1
Coupling unit A9BS for phase-
ground coupling or as second leg
for double-phase/intersystem
coupling

287
Application
The modular coupling units serve for:
- Insertion and extraction of PLC signals on Design
high tension overhead lines and cables.
The PLC coupling unit consists of the equipment
- Transiting of carrier signals in intermediate
housing, the filter module, drain coil, surge arrester
stations.
and the externally attached earth switch.
- Impedance matching between HT-line and
In double-phase or intersystem coupling
PLC equipment.
arrangements one of the both coupling units
- Electrical and galvanical separation of high
accommodates a hybrid transformer. The equipment
tension plant and PLC transmission unit(s).
enclosure, in grey color shade RAL 7032, is formed
by a polyester housing reinforced by glad fibre mats
Besides positive protection of personnel against
and meets protection standard IP 65 per DIN 40050
electrical shocks emphasis was placed on low
(German Industrial Norms). The hinged lid with
insertion loss for the coupling of the carrier signals.
profile gasket is pressed against the housing by
means of two latches which ensure absolute
Brief description tightness of the unit. Connection to the coupling
capacitance and earthing system is carried out via
Signal transmission threaded bolts M10 on the left of the apparatus. The
connecting cable to the PLC unit(s) is fed through
Transmission of PLC signals is effected via either a polyester glands PG16 at the bottom of the unit.
high-pass or band-pass circuit. The filter Termination of the coaxial cable is done over screw-
components consist of non-ferrite coils, low-loss type terminals whereby the braiding can be
capacitors and voltage proof ferrite transformer. additionally grounded by means of cable clamps.
The coupling unit permits the coupling of PLC Two vents at the unit’s bottom provide connection
signals within a frequency band which is determined to the outer atmosphere.
by the capacitance of the coupling capacitor (or All components are fully climate proof and,
CVT) and the impedance of the HT-line. Within this therefore, no need exists for the fitting of heating
frequency range the requirement are met with regard elements or other dehumidifying components.
to mismatch and attenuation as laid down in IEC
Publication 481. The high-pass coupling unit can be Protective measures
utilized wherever the coupling capacitance is higher
than 1,5 nF. It may be programmed to line Surge voltages caused by switching operations or
impedances of 240Ω or 320Ω and to PLC lightnings are absorbed and limited to a maximum
equipment impedances of 75Ω or 125Ω . The bank- of 4 kV by a surge arrester rated to kA absorption
pass coupling unit is factory tuned to the available current.
coupling capacitance and line impedance (overhead The matching and separating transformer is
line or cable). designed for a mains test voltage of 10kV. 1 min,
therewith providing a sage margin for isolating the
coupling capacitor’s HT potential against the PLC
equipment.
Fig. 2
The reactive current of the mains voltage is led to
Principle of PLC transmitter and receiver station
earth through the drainage coil. The low impedance
at mains frequency of this coil provides high
continuous and short-duration current capability.

288
Safe working on the coupling unit is enabled by
closing the earthing switch (rated 150 A) fitted
outside to the left of the apparatus.
The accommodation of the coupling units in
insulating poly-glass housings further contributes to
the high degree of safety against electrical hazards.

Universal hybrid transformer A1AC

The universal hybrid transformer can be employed
for the following tasks:
- Provision of the push-pull signal and
System modularity
decoupling function in double-phase or
inter-system coupling arrangements.
The modular coupling units MCD are designed such
- Patch-through and coupling network in
as to provide optimum and economical solutions for
PLC transit circuits.
a variety of coupling applications. In order to
- Patch-through and coupling network in
minimize spare part stocking and to facilitate
PLC transit circuits.
possible future extensions no individually tuned
- For paralleling of 2 PLC units’ little
components are foreseen for standard application.
frequency spacing.
Nevertheless, to cater also for special application, a
selection of tunable modules are available which fit
Bandpass coupling filter A9BP
into the “family” of MCD 80.
For application where the attainable frequency band
The system of MCD 80 comprises the following
of the programmable highpass filter is not sufficient,
components:
the individually tuned bandpass filter A9BP has to
be employed.
High pass coupling filter A9BS
Such applications are e.g. coupling to high-voltage
This is a polyglass equipment housing containing a
cables (low cable impedance) or if relatively low
highpass coupling filter of 4th order and its
frequencies have to be coupled via small coupling
associated protective device. The highpass filter is
capacitances.
programmable for various coupling capacitors, line
The filter is accommodated in the standard polyglass
and PLC equipment impedances. Together with the
housing together with its associated protective
coupling system for phase-to-ground coupling.
device.
There is space available within the housing to
accommodate additional components.
Bandpass coupling filter with hybrid transformer
A9BR. As with A9BP but with built-in hybrid
Single phase coupling (phase-to-ground)
transformer A1AC.

Separating A1AD
For directional separation of PLC channels intended
selective hybrid circuit. The filter features low
passband attenuation and high cross-band damping.
It has to be individually manufactured for the
particular task and is accommodated in a separate
housing.
Double-phase coupling
Attenuator A1AD
In order to improve line matching an attenuator
network is inserted in the transmission path. Typical
applications are line transmission systems with
excessive non-linear impedance.
289
RF junction network A1AF High pass filter with hybrid transformer A9BT
The RF junction A1AF forms a non-selective For double-phase or inter-system coupling the
coupling network. It is employed if more than two hybrid transformer A1AC is already mounted in the
terminals work on the same frequency pair (e.g. housing of the highpass filter A9BS. Consequently,
wave-changeover installations). for double-phase (intersystem) coupling each a
coupling unit A9BS and A9BT is required.
Impedance transformer A1AE
If impedances are desired which are not covered by
the standard impedance of the MCD 80 a matching
transformer type A1AE can be employed.
Technical data
Diagram highpass coupling filter A9BS

Programmable frequency bands

Lower frequency limit f (kHz)

C8 1500 2000 2700 3300 3900 4700 5600 6800 7500

Z1 PF to to to to to to to to and
Ω 2199 2699 3299 3899 4699 5599 6799 7499 up

240 232 158 132 115 96 80 70 60 52

320 180 129 102 90 78 76 70 58 52

C8 : coupling capacitance
Z1: impedance of overhead line
Upper frequency limit f2 = 500 [kHz]

Bandpass coupling unit A9BP

The attainable frequency ranges can be calculated by using the following formula:

290
 f1
−7.
F2 = 2.5 .10 π . f 1 . C2 . Z 1 F2 : upper frequency limit
C2 +1.0 . 10−7.
[Hz]
F1 : lower frequency limit [Hz]
C8 : coupling capacitance [F]
Z1 : impedance of high tension line [Ω ]

Technical Data (continued)

Highpass filter A9BS / A9BT

Nominal impedance PLC equipment side Z2 75/125Ω unbalanced

transmission line side Z1 240/320 Ω

Range of coupling capacitance 1.5 to 13 nF

Composite loss within passband ≤1.0 dB

(phase/ground)
≤ 1.5 dB
(phase/phase)

Return loss within passband ≥ 12dB

Bandpass filter A9BP / A9BR

Nominal impedance PLC equipment side Z2 as desired

transmission line side Z1 as desired

Range of coupling capacitance min. 0.5 nF

Composite loss within passband typical 1.5 dB

Return loss within passband, typical 12dB

Common filter properties

Average continuous power (freq.dep.) typical 200W

Nominal peak power P.E.P at 50 kHz ≤ 400 W

at 100 kHz ≤ 1000 W

non-linear distortion
(2-tone test P.E.P 400W. F1=54/kHz. F2 = 66 khz
Intermodulation 3rd & 5th order ≥ 80 dB
Harmonic distortion ≥ 80 dB
291
 Power frequency test voltage
Transformer (primary / secondary) 10kV rms.
1min
Hybrid (windings / windings) 5kV rms. 1
min

Impulse test voltage, wave shape 1.2 / 50μs

Transformer (input line / ground 10kV peak
Hybrid (inputs against ground) 5kV peak

Crossover attenuation of hybrid A1AC ≥ 20 dB

Drail coil

Highpass A9BS /A9BT

Inductivity adjustable 0.2 to 0.7 mH
Impedance at mains frequency ≤ 1.5 Ω

Bandpass A9BP / A9BR

Inductivity 40 mH
Impedance at mains frequency ≤ 20 Ω

Common features
Continuous current ≤ 1.5 A rms
Short time current ≤ 50 a. 0.2s

Earthing switch

Rated current 150A rms

Lightning arrester Type BBC RV 0.66

Rated voltage 660V

Min. spark over voltage at power frequency 1300 V rms
Max. 100% impulse spark over voltage (1.2/50μs) 3300 V peak
Rated discharge current (8/20μs) 5 kA peak
Impulse withstand current (4/10μs) 30 kA peak
Ability to withstand waves of a long duration 75 A 1000μs
Max. residual voltage at rated discharge current 3300 V

Connections

Equipment side
Terminal blocks for max. cross section 4 sqmm
Cable glands PG 16 for cable diameter 7-15mm

292
 Line side and earthing
Commenting bolts with metric threading M 10

Permissible ambient temperature range -40℃ to

70℃

Weight (per unit)

A9BS, A9BP approx. 9kg (20 lbs)

A9BT, A9BR approx. 10kg (22 lbs)

Designed and manufactured with requirement in accordance with requirements and recommendations
of IEC 481,SEV 3052.
DIMENSIONS

ABB
ASEA BROWN BOVERI

Asea Brown Boveri Ltd

Communications and Information Systems
293
CH-5300 Turgi / Switzerland

Dept. ENF/ Power System Communications

Phone 056/29 96 11, telex 82829150 ab ch

TRANSFORMER AND TRANSFORMER – FEEDER PROTECTION

16.1
16.2
16.3
16.4
16.5
16.6
16.7
16.8
16.9
16.10
16.11
16.12
16.13
16.14
16.15

16.1

The power transformer is one of the most important

links in a power transmission and distribution
system. It also possesses a wide range of
characteristics and certain special features which
make complete protection difficult. These
conditions must be reviewed before the detailed
application of protection is considered.
The choice of suitable protection is also governed
by economic considerations. Although this factor is
not unique to power transformers. It is brought into
prominence by the wide range of transformer ratings
used in transmission and distribution systems which
can vary from a few kVA up to several hundred
MVA. Only the simplest protection such as fused
can be justified for transformers of the lower ratings
whereas those of the highest ratings should have the
best protection that can be designed.
294
16.2
NATURE AND EFFECTS OF
TRANSFORMERS FAULTS Figure 16.1 Earth fault current in resistance earthed
star winding
A fault on a transformer winding is controlled in
magnitude not only by the source and neutral 16.2.2
earthing impedance but also by the leakage Star-connected winding with neutral point
reactance of the transformer and the fact that the solidity earthed
fault voltage may differ from the system voltage The fault current in this case is controlled mainly by
according to the position of the fault in the winding. the leakage reactance of the winding, which varies
Several distinct cases arise these are examined in a complex manner with the position of the fault.
below. The variable fault point voltage is also an important
factor as in the case of impedance earthing, but the
16.2.1 reactance decreases so rapidly for points
Star-connected winding with neutral point approaching the neutral that the fault current is
earthed through an impedance actually highest for a fault near the neutral end of
the winding. The variation of current with fault
An earth fault on such a winding will give rise to a position is shown in Figure 16.2
current which is dependent on the value of the
earthing impedance, and is also proportional to the
distance of the fault from the neutral point, since the
fault voltage will be directly proportional to this
distance.

The ratio of transformation between the primary

winding and the short-circulated turns also varies
with the position of the fault, so that the current
which flows into the transformer primary terminals
will be in proportion to the square of the fraction of
the winding which is short-circuited. The effect is
shown in Figure 16.1 from which it may be noticed
that faults in the lower third of the winding produce
very little current through the line connections.

The fault current as modified as before by the

variable transformation ratio to give the input
current as the fault current magnitude stays high
throughout the winding and further, the general
scale of current is high in the absence of external
limiting impedance, the input current curve remains
at a substantial level for faults at most points along
the winding.

16.2.3
Delta-connected winding
No part of a delta connected winding operates with a
voltage to earth of less than 50% of the phase
voltage. The range of fault current magnitude for
such a winding is therefore less that for a star
winding. The actual value of earthed, it should also
be remembered that the impedance of a delta
winding is particularly high to fault currents flowing
to a centrally placed fault on one leg. The
295
impedance can be expected to be between 25% and Core faults
50% based on the transformer rating regardless of A conducting bridge across the laminated structure of the
core can permit sufficient eddy-current to flow to cause
the normal balanced through-current impedances.
serious overheating. The bolts which clamp the core
As the prefault voltage to earth at this point is half together are always insulated, to avoid this trouble. If any
the normal phase voltage, the earth fault current may portion of the core insulation becomes defective the
be no more than the rated current or even less than resultant heating may reach a magnitudes sufficient to
this value, if the source or system earthing damage the winding.
The additional core loss, although causing severe local
impedance is appreciable. The current will flow to
heating will not produce a noticeable change in input
the fault from each side through the two half current and could not be detected by the normal electrical
windings and will be divided between two phases of protection. It is nevertheless highly desirable that the
the system. The individual phase currents may condition should be detected before a major fault has been
therefore be relatively low., a fact which must be created. Fortunately, in an oil-immersed transformer, if
the heating of any part of core structure is sufficient to be
remembered when considering the performance of a liable to cause damage to the winding insulation. It will
protection scheme. also cause breakdown of some of the oil with an
accompanying evolution of gas. This gas will escape to
16.2.4 the conservator and is used to operate a mechanical relay;
Phase to phase faults see Section 16.13.3.
Faults between phases within a transformer are 16.2.7
relatively rare, if such a fault does occur it will give Tank Faults
rise to a substantial current comparable to the earth
fault currents discussed in Section 16.2.2. Loss of oil through tank leaks will ultimately produce a
dangerous condition, either because of a reduction in
winding insulation or because of overheating on load due
16.2.5 to the loss of effective cooling.
Interturn faults Oil sludging can block cooling ducts and pipes, leading to
In low voltage transformers, interturn insulation overheating on load. A similar effect is produced by the
breakdown is unlikely to occur unless the failure of the forced cooling systems applied to large
mechanical force on the winding due to external transformers.
short circuits has caused chafing or cracking of the 16.2.8
insulation or moisture has been admitted to the oil. Externally applied conditions
A high voltage transformer connected to an Sources of abnormal stress in a transformer are:
overhead transmission system is very likely to be a) Overload.
subjected to steep fronted impulse voltages. A line b) System faults.
c) Overvoltage.
surge which may be of several times the rated d) Reduced system frequency.
system voltage will concentrate on the end turns of Overload causes increased copper loss and a consequent
the winding because of the high temperature rise. Overloads can be carried for limited
periods depending on the initial temperature and the
cooling conditions (see BS Code of Practice CP1010:
Guide to Loading of Transformers).
The thermal time constant of ONAN (Oil Natural Air
Natural) transformers is of the order of 2.5 – 5 hours.
Shorter time constant will apply to force-cooled
transformers. System short circuits produce a relatively
Insulation of the end turns is reinforced but cannot be intense rate of heating of the feeding transformers, the
copper loss increasing in proportion to the square of the
increased in proportion to the insulation to earth, which is
per unit fault current. The duration of external short
relatively great. The risk of a partial winding flash-over
circuits that a transformer can sustain without damage if
compared with that of a breakdown to earth is therefore
the current is limited only by self-reactance is typically
comparatively high. It is claimed that 70% - 80% of all
shown in Table 16.1.
subsequent progress of the fault, if not detected in the
earliest stage may well destroy the evidence of the true Transformer Fault current Permitted fault
cause. reactance (%) (multiple of rating) duration
A short-circuit of a few turns of the winding will give rise (seconds)
to heavy fault current in the short-circuited loop, but the 4 25 2
terminal currents will be very small, because of the high 5 20 3
ratio of transformation between the whole winding and the 6 166 4
short-circuited turns. 7 142 5
The graph in Figure 16.3 shows the corresponding data for Table 16.1 Fault withstand level
a typical transformer of 3.25% normal through impedance
with the short-circuited turns symmetrically located in the Large fault currents produce severe mechanical stresses in
centre of the winding. transformers; the maximum stress occurs during the first
cycle of a systematic fault current and so cannot be
16.2.6

296
averted by automatic tripping of the circuit. The control of
such stresses is therefore a matter of transformer design.
Overvoltage conditions are of two kinds:
(i) Transient surge voltages.
(ii) Power surge voltages.
Transient overvoltages arise from switching and lightning
disturbances and are liable to cause interturn faults as
(b) STEADY AND MAXIMUM OFFSET FLUXES
described in Section 16.2.5. these overvoltages are usually
limited by shunting the high voltage terminals to earth
either with a plain rod gap, the so-called coordinating gap
or by surge diverters which comprise a stack of short gaps
in series with a non-linear resistor. The surge diverter has
the advantage of extinguishing the flow of power current
after discharging a surge, in this way avoiding a system (c) TYPICAL INRUSH CURRENT
fault that would require the transformer to be isolated
which is what happens with the simple protective gap.
Power frequency overvoltage causes both an increase in
stress on the insulation and a proportionate increase in the
working flux. The latter effect causes an increase in the
iron loss and a disproportionately great increase in
magnetizing current. In addition, flux is diverted from the
laminated core structure into steel structural parts. In
particular, under conditions of over-excitation of the core,
the core bolts which normally carry little flux, may be
subjected to a large component of flux diverted from the (d) INRUSH WITHOUT OFFSET DUE TO YOKE
highly saturated and constricted region of core alongside. SATURATION

Under such condition, the bolts may be rapidly heated to a Figure 16.4 Transformer magnetizing inrush
temperature which destroys their own insulation and will
damage the coil insulation if the condition continues. When an inductor is energized by a steady alternating
Reduction of frequency has an effect with regard to flux voltage, the flux linking the inductive circuit varies from a
density, similar to that of overvoltage. peak negative value to an equivalent peak positive value
It follows that a transformer can operate with some degree during one half cycle of the voltage wave. The flux
of overvoltage with a corresponding increase in change of twice the maximum flux value is proportional
frequency, but operation must not be continued with a
to the time integral of the voltage wave between
high voltage input at a low frequency.
successive zero points. On switching on at the zero point
Operation cannot be sustained when the ratio of voltage to of the wave, the full flux change is required during the
frequency with these quantities given values per unit of first half cycle, but with the flux initially zero, the
their rated values, exceeds unity by more than a small maximum flux developed will be nearly twice the normal
amount, for instance if V/f ¿ 1.1. the bade of unit voltage peak value as shown in Figure 16.4 (b).
should be taken as the highest voltage for which the If the inductor is linear, as for example is an air-cored
transformer is designed if a substantial rise in system inductor the current taken will also rise to nearly twice the
voltage has been catered for in the design. steady state value. A transformer primary winding
however can be treated as an iron-cored inductor in which
16.3 the normal peak flux is close to saturation value. An
MAGNETIZING INRUSH increase of the flux to double this value corresponds to
The phenomenon of magnetizing inrush is a transient extreme saturation. The magnetizing current therefore
condition which occurs primarily when a transformer is
rises to a very high value which may exceed the rated full
energized. It is not a fault condition and therefore does not
load value – hence the term current inrush.
necessitate the operation of protection which on the
contrary must remain stable during the inrush transient, a Residual flux can increase the current still further. If the
requirement which is a major factor in the design of initial remanent flux, instead of being zero has an initial
protective systems for transformers. positive value that is an initial value in the same direction
as the flux change the increment of flux must remain the
same, since it is proportional to the half cycle voltage loop
and the peak value attained will be of the order of 2.8
times the normal value with 80% remanence.
The very high flux densities quoted above are so far
beyond the normal working range that the incremental
relative permeability of the core approximates to unity and
the inductance of the winding falls to a value near that of
the air cord inductance. The current wave starting from
(a) TYPICAL MAGNETIZING CHARACTERISTIC zero increases slowly at first, the flux having a value just
above the residual value and the permeability of the core
being moderately high. As the flux passes the normal
working value and enters the highly saturated portion of
the magnetizing characteristic the inductance falls and the
297
current rises rapidly to a peak which may be five hundred the current phases through a range of conditions. Even the
times the steady state magnetizing current. When the peak inrush current shown in figure 16.4 (d) which has no
is passed at the next voltage zero, the following negative offset, is not symmetrical about the horizontal axis but
half cycle of the voltage zero, the following negative half possesses mirror image symmetry about chosen ordinates.
is passed at the next voltage zero, the following negative This waveform, therefore, possesses even as well as odd
half cycle of the voltage wave reduces the flux to the harmonics.
starting value, the current falling systematically to zero:
see Figure 16.4(c). the current wave is therefore fully 16.4
offset and as with the offset wave in a linear inductor is OVERHEATING PROTECTION
only restored to the steady state condition by the circuit The rating of a transformer is based on the temperature
losses. The time constant of the transient is relatively long rise above an assumed maximum ambient temperature
being from perhaps 0.1 seconds for a 100kVA transformer under this condition no sustained overload is usually
and up to 1.0 seconds from a large unit. As the permissible. At lower ambient temperature some degree of
magnetizing characteristic is non-linear, the envelope of overload can be safely applied. Short period overloads are
the transient current is not strictly of exponential form; the also permissible to an extent dependent on the previous
magnetizing current can be observed to be still changing loading conditions. No precise ruling applicable to all
up to 30 minutes after switching on. conditions can be given concerning the magnitude and
Switching at other instants of the voltage wave produces duration of safe overload.
lower values of transient current. If the point on the wave The only certain statement is that the winding must not
is chosen so that the residual flux is the correct value for overheat; a temperature of about 95℃ is considered to be
that instant under steady conditions, no transient will the normal maximum working value beyond which a
occur and the steady no-loud current will occur and the further rise of 8° - 10℃ if sustained will halve the life of
steady no-load current will be taken immediately. the unit.
In the case of three-phase transformers, the point on-wave Protection against overload is therefore based on winding
at switch on differs for each phase and different inrush temperature, which is usually measured by a thermal
currents are drawn in consequence. Some inter-phase image technique.
mutual interference also takes place because of the The thermal sensing element is placed in a small pocket
combination of the phase fluxes in the yoked. In this way
it is possible for a phase with a point on-wave- of
energization which in itself would produce no inrush
transient to receive nevertheless an inrush current of
substantial magnitude. In this case the current wave from
will not be offset from the zero axis but will be distorted,
generally as shown in Figure 16.4 (d).

16.3.1
Harmonic content of inrush waveform
The waveform of transformer magnetizing current
contains a proportion of harmonics which increases as the
peak flux density is raised to the saturating condition. As
long as the waveform is symmetrical about the horizontal
axis, only odd harmonics will be present. The condition is
typical for normal alternating currents flowing through
impedances which have no directional polarizing
property. The magnetizing current of a transformer is of
this class and will contain a third harmonic and
progressively smaller amounts of fifth and higher
harmonics. If the degree of saturation is progressively
increased, not only will the harmonic content increase as a
whole but the relative proportion of fifth harmonic will
increase and eventually overtake and exceed the third
harmonic. At a still higher level the seventh would
overtake the fifth harmonic but this involves a degree of
saturation that will not be experienced with power
transformers.

The energizing conditions which result in an offset inrush

current produce a waveform which is not symmetrical
about the horizontal axis but which is symmetrical,
neglecting decrement about certain ordinates. Such a wave ……………………………………………
third harmonics and diminishing amounts of higher voltage technical of one phase, is also located in this
orders. As with the steady state wave, the proportion of pocket and produces a local temperature rise, similar to
harmonics varies with the degree of saturation, so that as a that of the main windings above the general oil
severe inrush transient decays, the harmonic makeup of temperature.
298
The sensing element therefore experiences a temperature transformer has been overheated to a given degree,
similar to that of the winding under all conditions thereby building up the life history of the unit as far as
correctly taking into account the effects of ambient heating and building up the life history of the unit as far as
temperature and previous loading history. heating and consequent deterioration of the insulation is
Dial thermometers comprising of a pressure-type concerned. In the type CTTT temperature-time integrator,
instrument connected by capillary tubing to a bulb in the electrolytic coulometers are used. The meter element is a
oil pocket and filled with a suitable liquid have been glass capillary tube filled with mercury. The indicating
extensively used in the past. gap is the electrolyte. When a small current, about 1 μA is
A well-proven system is provided in the type TTT relay. passed through the coulometer, mercury is transferred
Here the sensing element is a heat sensitive silicon resistor from the anode to the cathode, thereby moving the end of
or Silistor which is incorporated with the heating element the mercury column across the scale in 10,000 hours.
in a thermal mass of molded material, the whole forming a Four coulometers are used. The signal form the resistance
thermal replica of the transformer winding. The replica bridge in the type TTT overheating protection relay is
which is in the form of a short cylinder is placed in the applied via separate level detector circuits and reed output
pocket in the transformer tank about ten inches below the relays to the coulometers, the detectors being adjusted to
tank top, which is estimated to be the hottest layer in the switch at successive selected temperatures and a positive
oil. The scheme is indicated in Figure 16.5. interlock being used to ensure that only one coulometer is
The Silistor forms one arm of a resistance bridge which is energized at any one time. Thus each indicator measured
energized from a stabilized d.c. source. The unbalance only in the band between its own setting and the next
output signal energizes an indicating instrument and the higher one. The temperature bands usually chosen are:
voltage across the Silistor is applied to static sensing 100 - 110℃ 10,000 hours for full scale
circuits, which control forced cooling pumps and fans 110 - 120℃ 10,000 hours for full scale
give warnings of overheating and ultimately trip the 120 - 130℃ 10,000 hours for full scale
transformer circuit breakers. 130℃ and above 10,000 hours for full scale
The instrument will therefore indicate for how long the
The control circuits are arranged to reset with a definite winding temperature has been in each temperature band,
but adjustable differential. The alarm and trip outputs do which is sufficient to enable a reasonable estimate of the
not require this feature locally or remote, or indication at degree of ageing of the transformer to be made.
both locations can be given.
16.5
OVERCURRENT PROTECTION

16.5.1
Fuses
Small distribution transformers are commonly protected
by fuses. In many cases no circuit breaker is provided
making fuse protection the only available means of
automatic isolation. Fuses are overcurrent devices, and
must have ratings well above the maximum transformer
load current in order to carry, without ‘blowing’, the short
duration overloads that may occur because of such as
motor starting also, the fuses must withstand the
magnetizing inrush currents drawn when power
transformers are energized. Moreover, high Rapturing
Capacity (HRC) fuses, although very fast in operation
with large fault currents, are extremely slow with currents
of less than three times their rated value. It follows that
such fuses will do little three times their rated value. It
follows that such fuses will do little to protect the
transformer, serving only to protect the system by
disconnecting a faulty transformer after the fault has
reached an advanced stage.
The above remarks will be made clear in Table 16.2,
which shows typical ratings of fuses for use with 11kV
transformers

Transformer rating Fuse

kVA Full load current Rated Operating time at
(A) Current (A) 3 x rating (s)

16.4.1 100 5.25 16 3.0

200 10.5 25 3.0
Temperature-time integrator
300 15.8 36 10.0
A further refinement in the supervision of a transformer is
500 26.2 50 20.0
obtained by integrating the periods during which the
299
1000 52.5 90 30.0 The system is operative for faults within the region
Table 16.2 Typical ratings between current transformers, that is, for faults on the star
winding in question. The system will remain stable for all
………………………………… characteristics of faults outside this zone.
different types of HRC fuses. Furthermore, grading with
protection on the secondary side has not been considered.

16.5.2
Overcurrent relays
The larger transformers 100 kVA and over may be
controlled by circuit breakers in which case protection can
be provided by overcurrent trips or by relays.
Improvement in protection is obtained in two ways; the
excessive delays of the HRC fuse for the lower fault Figure 16.6 Restricted earth fault protection for a star
current are avoided and an earth fault tripping element is winding
provided in addition to the overcurrent feature.
The time delay characteristic should be chosen to The gain in protection performance comes not only from
discriminate with circuit protection on the secondary side. using an instantaneous relay with a low setting but also
Instantaneous trips may be added; the current setting because the whole fault current is measured not merely
being chosen to avoid operation with a short circuit on the the transformed component in the HV primary winding.
secondary side. Alternatively, HRC fuses may be used to Hence, although the prospective current level decreases as
back up the circuit breaker. Although full discrimination fault positions progressively nearer the neutral end of the
with the secondary circuit protection is necessary, the fuse winding are considered, the square law which controls the
rating need not be as high as through fault current,; the primary line current is not applicable and with a low
time characteristic of the fuse can be taken into account effective setting a good percentage of the winding can be
and discrimination is likely to be obtained with fuses rated covered.
at between 2 and 6 times the transformer full load current Restricted earth fault protection is often applied even
depending on the transformer reactance, the source fault when the neutral is solidity earthed. Since fault current
power and whether the secondary system is a single then remains at a high value even to the last turn of the
circuit or subdivided into several branches each with winding (Figure 16.2), virtually complete cover for earth
individual protection. faults is ………………………………… the performance
The main function of such instantaneous protection is to of systems which do not measure the neutral conductor
give high speed clearance of terminal short circuits, the current.
settings therefore may be made relatively high.
The primary winging of a distribution transformer will not
usually be earthed making reverse flow of earth fault
current and time, the limitation being entirely on account
of the performance of the current transformer. An
excessively low relay current setting may give a poor
effective setting as discussed in Section 9.16.
In order to maintain good discrimination the earth fault
element should remain stable under phase fault conditions,
which is more likely to be achieved with a low relay
setting because of the high impedance of the rely on a low
tap between the conflicting requirements of sensitivity and
stability.
In phase fault stability is achieved, the time setting can be
reduced to the minimum value, since time grading of earth Figure 16.7 Principle of transformer differential
fault elements is not involved. protection

16.6
RESTRICTED EARTH FAULT PROTECTION

A simple overcurrent and earth fault will not give good

protection cover for a star-connected primary winging,
particularly if the neutral is earthed through an impedance
as considered in Section 16.21. the degree of protection is
very much improved by the application of a unit
differential earth fault system or restricted earth fault
protection as shown in Figure 16.6. the residual current of
three line current transformers is balanced against the
output of a current transformer in the neutral conductor.
The relay is of the high impedance type, the theory of
which is set out in Section 10.4.1.
300
 the rated current will depend on the MVA rating of the
relevant winding. Line current transformers should
therefore have primary ratings equal to or above the rated
Earth fault protection applied to a delta-connected or currents of the transformer windings to which they are
unearthed star winding is inherently restricted, since no applied. Primary ratings will often be limited to those of
zero sequence component can be transmitted through the available standard ration CTs. For example, current
transformer to the secondary system. A high impedance transformers of 1600/1A and 200/1A have been chosen
relay can therefore be used giving fast operation and for the protection of the two winding 11kV/132kV, 30
phase fault stability. MVA transformer considered in Section 16.71 (d).
Both windings of a transformer can be protected
separately with restricted earth fault protect thereby b) Current transformer connection
providing high speed protection against earth faults for the The CT connections should be arranged, where necessary
whoa transformer with relatively. to compensate for phase differences between line currents
on each side of the power transformer. If the transformer
16.7 is ……………………………………………………which
must be corrected in the CT secondary leads by
The restricted earth fault schemes described above in appropriate connection of the CT secondary leads by
Section 16.6 depend entirely on the Kirchoff principle that appropriate connection of the CT secondary windings.
the sum of the currents flowing into conducting network is
zero. A differential system can be arranged to cover the
complete transformer operation and the close equivalence
of ampere-turns developed on the primary and secondary
windings. Figure 16.7 illustrates the principle. Current
transformers on the primary and secondary sides are
connected to form a circulating current system.

16.7.1
Basic considerations for transformer differential
protection

a) Line current transformer primary ratings

The rated currents of the primary and secondary sides of a
two winding transformer will depend on the MVA rating Diagram
of the transformer and will be inverse ratio to the
corresponding voltages. For three winding transformers

301
CONNECTIONS FOR BIASED RELAYS CONNECTIONS FOR UNBIASED RELAYS
NOTES ON RELAY CONNECTIONS

1. Connection ‘k’ or ‘I’ is omitted when corresponding CT’s are delta-connected. When both sets of CT’s are delta-
connected ‘k’, ‘I’ and ‘m’ are on.
2. it is essential that CT connections are earthed at one point only.
3. When the power transformer to be protected has 3 windings, it may be helpful to consider firstly the relative
connection for the CT’s associated windings 1 and 2 and then those with windings 1 and 3. As a final check the
relation between the CT’s on windings 2 and 3 may be considered.
4. The power transformer vector group references correspond to those specified in IEC 76: 1967 and BS 171:1970

Figure 16.9 Current transformer connections for power transformers of various vector groups
if the transformer has a tapping range enabling its ratio to
Furthermore, zero sequence current flowing on the star be varied, this must be allowed for I the differential
side of the power transformer will not produce current system. This is because if the current transformers are
outside the delta on the other side. The zero sequence chosen to balance for the mean ratio of the power
must therefore be eliminated from the star side by transformer a variation in ratio from the mean will create
connecting the current transformers in delta from which it an unbalance proportional to the ratio change. At
follows that the current transformer on the delta side of maximum through fault current, the spill output produced
the transformer must be connected in star, in order to give by the small percentage unbalance may be substantial.
the 30° phase shift. This is a general rule: if the Differential protection should be provided with a
transformer were connected star/star, the current proportional bias of an amount which exceeds in effect the
transformers on both sides would need to be connected in maximum ration deviation. This stabilizes the protection
delta. under through fault conditions while still permitting the
When current transformers are connected in delta, their system to have good basic sensitivity.
√
secondary ratings must be reduced to 1/ 3 times the The bias characteristic for a typical differential protection
is shown in Figure 16.10 from which it can be seen that
secondary rating of star-connected current transformers, in
order that the currents outside the delta may balance with the
the secondary currents of the star-connected current
transformers.
When line CT rations provide adequate matching between
currents supplied to the differential relay under through-
load and through-fault conditions, the necessary phase
shift can be obtained by suitable connection of the line
CTs. Figure 16.9 shows the required connections for
various power transformer winding arrangements.
When delta connected CTs are required it is a common
alternative practice to use star connected line CTs and to
obtain the delta connection by means of star/delta
interposing CTs, as exemplified in Section 16.7 (d). Figure 16.10 Typical bias characteristic

c) Bias to cover tap-changing facility and CT mismatch Current required to operate the relay increases as the
through-fault current increases.
302
When applying a differential relay, care should be taken besides their use for phase compensation interposing CTs
that its characteristic will prevent operation due to the may be used to match up currents supplied to the
combination of tap change variation and CT mismatch. To differential protection form line CTs for each winding. As
…………………………………………………………… previously described, the amount of CT mismatch which a
….. the differential relay are usually matched at the mid- relay can tolerate without maloperation under through
point of the tap range. current conditions will depend on its bias characteristic
Figure 16.8 shows percentage bias differential protection and the range over which the tap changer can operate. If
for a two winding transformer. The two bias windings per the combined mismatch due to CTs and tap changer is
phase are commonly provided on the same electromagnet above the acceptable level, then interposing CTs may be
or auxiliary transformer core. used to achieve current matching at the mid point of the
The Merz-Price principle remains valid for a system tap changer rang.
having more than two connections, so a transformer with For the protection of two winding transformers,
three or more windings can still be protected by the interposing CT’s should ideally match the relay currents
application of the above principles. under though load conditions corresponding to the
When the power transformer has only one of its three maximum MVA rating of the transformer.
windings connected to a source of supply with the other An example of this for an 11kV/132kV , 30MVA
two windings feeding loads at different voltages, a relay delta/star transformer is shown in Figure 16.12.
of same design as that used for two-winding transformer First, the primary ratings of 1600A and 200A chosen for
can be employed, connected as shown in Figure 16.11(a). the main current transformers should not be less than the
the separate loads currents are summated in the CT maximum full load currents in each winding which are:
secondary circuits and will balance with the infeed current 6
30 x 10
on the supply side. = 1575 A for the 11kV winding
When more than one winding is connected to a source, the √3 x 11 x 103
distribution of current cannot readily be predicted and
there is danger in the scheme in Figure 16.11 (a) of And
current circulating between the two paralleled sets of
current transformers without producing any bias. It is 6
30 x 10
therefore important that bias be obtained separately from = 164 A for the 132kV
the current flowing in each set of line connection. In this √3 x 0.8 x 132 x 103
case a relay is used with separate bias windings, arranged winding
so that their mechanical or electrical effects always add
numerically, that is not vectorially to give the total bias For the 11kV winding this is also the nominal full load
effect. This is shown in Figure 16.11 (b). current, but for the 132kV winding with -5% tap, the latter
These considerations do not apply when the third winding is:
consists of a delta-connected tertiary with no connections
6
brought out. Such an arrangement may be regarded as a 30 x 10
two winding transformer for protection purposes and may = 138 A
be protected as shown in Figure 16.11 (c). √3 x 0.95 x 132 x 103
d) interposing CTs to compensate for mismatch of line
CTs

(a) THREE WINDING TRANSFORMER (one power source)

303
(b) THREE WINDING TRANSFORMER (three power sources)

(C) THREE WINDING TRANSFORMER WITH UNLOADED DELTA TERTIARY

Figure 16.11 Biased differential protection arrangements shown as single phase diagrams for simplicity

Equivalent secondary currents in the line CTs are 0.984 A 6

90 x 10
and 0.69A. thus the ratio of the star /delta interposing CTs Load current at 138kV = =
to achieve ideal matching is given by: √3 x 138 x 103
376.5
0.69 /
0.984 1
= 0.70 ¿ A or 0.70 / 0.577A
√3 √3 30 x 10
6
Load current at 13.45kV = =
The protection of three winding transformers is √3 x 13.45 x 103
complicated by the fact that line CTs for each winding are 12….
normally based on different MVA levels and will not
themselves achieve balance under through current Line CT ratio at 500kV = 200/5A
conditions. To achieve correct balance, it is necessary to
Line CT ratio at 138kV = 400/5A
use interposing CTs which will provide the relay with
rated current when the rating of the highest rated winding Line CT ratio at 13.45kV = 1500/5A
is applied to all windings. Current at 138kV corresponding to 120 MVA
6
120 x 10
An example for a 500kV/138kV/13.45 kV,120 = = 5…
MVA/90VA/30MVA, star/star/delta transformer is shown √3 x 138 x 103
in Figure 16.13

6
120 x 10
Load current at 5000kV = = 138
√3 x 500 x 103
A

304
Figure 16.12 Example of differential protection applied to a two winding transformer showing use of interposing current
transformers

Current at 13.45KV corresponding to 120MVA Under full load conditions of 30 MVA for the 13.45kV
6 delta winding, the current appearing in the primary of the
120 x 10
= = 5151A 17.17 / 5A interposing CT will be only 4.29A, the
√3 x 13.45 x 103 corresponding secondary current being 1.25A. however
the ratings of the primary and secondary windings should
Secondary current from 500kV line CTs corresponding to ideally be 17.17A and 5A respectively to minimize
120MVA winding resistances.
138.6 x 5
= = 3.46 A 16.7.2
200
Stabilization of differential protection during
magnetizing inrush conditions.
therefore ratio of required star / delta interposing CTs
5 The magnetizing inrush phenomenon described in Section
=3.46 / A or 3.46/2.89A
√3 16.3 produces current input to the energized winding
which has no equivalent on the other sides of the
transformer. The whole of the inrush current appears,
Secondary current from 138kV line CTs corresponding therefore, as unbalance and superficially is not
120MVA distinguishable from internal fault current. The normal
502 x 5 bias is not, therefore, effective and increase of the
= = 6.28A
400 protection setting to a value which would avoid operation
would make the protection of little value.
therefore ration of required star/delta interposing CTs
Time delay
5 Since the phenomenon is transient, stability can be
= 6.28 / A or 6.28 / 2.89A maintained by providing a small time delay. This has been
√3 achieved by v
Secondary current from 13.45kV line CTs corresponding
to 120MVA An instantaneous relay can be shunted by a fuse link, a so-
5151 x 5 called kick-fuse, thereby diverting most of the current.
= = 17.17A The fuse is chosen so as to carry the inrush transient
1500 without blowing: only in the event of an internal fault
does the fuse blow and permit the relay to operate.
Therefore ration of required star/star interposing CTs
Induction pattern relays of the I.D.M.T. type can also be
= 17.17/5A used to give a suitable time delay.

The type DDT induction pattern relay has both a suitable

various means.

305
Figure 16.13 Example of differential protection applied to a three winding transformer showing use of interposing current

Time characteristic as also a through-bias feature. Two point on the voltage wave, then no transient disturbance
induction electromagnets operate on a single disc, to should take place on that phase.
produce apposed torques. The elements are connected into
a Merz-Price system as shown in Figure 16.8, the setting Large inrush currents will flow in the other two phase
being adjustable from 40-100%, the bias slope can be corresponding to high peak flux values established in
selected by taps to be either 20%, 30% or 40%. phase cores. The high flux circulates through the yoke
saturation of which affects the first phase, which we have
A small time delay in operation is produced by an had no inrush effect, causing a substantial tran……
appropriate movement of the disc in combination with the current to flow in this phase as well. This latter ……
braking action on the disc of a permanent magnet. The however, will not be offset from the zero axis, although
operating time at five times the setting current is current waveform will be distorted; see Figure 16.4 (…)
adjustable between 100 and 250 milliseconds. A mid- stabilize a differential system, some sort of cross-phase
adjustment to about 120 milliseconds will usually be biasing would be required because of this effect.
found to be satisfactory.
Since many fault current waveforms will have initial
The above time delay might be thought insufficient to offset delay in tripping would result from the use of this
give stability with a severe inrush current.in practice it is component.
generally sufficient arising from the relatively poor
response of the induction element to uni-directional (b) Second harmonic
current.
This component is present in all inrush waveforms. It is
Harmonic restraint typical of waveforms in which successive half period
portions do not repeat with reversal of polarity but in
If damage to important transformers is to be minimized it which mirror-image symmetry can be found about certain
is essential to clear faults without delay and another ordinates.
solution to the inrush phenomenon must be found.
The proportion of second harmonic varies somewhat with
The inrush current, although generally resembling an in- the degree of saturation of the core, but is always present
zone fault current, differs greatly when the waveforms are as long as the uni-directional component of flux exists. It
compared. The distinctive difference in the waveform be has been shown to have a minimum value of about 20% of
used to distinguish between the conditions. the amount by which the inrush current exceeds the steady
stat magnetizing current.
As stated before, the inrush current contains all order
harmonic, but these are not all equally suitable for proving The waveform discussed in (a) above and shown in figure
bias. The study of this subject is complex, and waveform 16.4 (d) contains a typical proportion of second harmonic
depends on the degree of saturation and a grade on iron in component, since although not offset, it arises from a uni-
the core. The principal conclusions can summarized as directional flux.
follows. Normal fault currents do not contain second or other even
harmonics, nor do distorted currents flowing in saturated
(a). D.c or offset component (zero harmonic) iron cored coils under steady state conditions.
The output current of a current transformer which is
A uni-directional component will usually be present energized into steady state saturation will also contain odd
inrush current of a single-phase transformer and in harmonics but not even harmonics. However, should the
principle inrush currents of a three-phase unit. However, current transformer be saturated by the transient
at the instant of switching the residual flux for any is component of the fault current, the resulting saturation is
equal to the flux which would exist in the steady so that not symmetrical and even harmonics are introduced into
the output current. This can have the advantage of
306
improving the through fault stability performance of a
differential relay, but it also has the adverse effect of A still smaller proportion of fifth harmonic will be
increasing the operation time for internal faults. present. This component is not subject cancellation as is
the third harmonic and can be present in the output of a
The second harmonic is therefore an attractive basis for a CT in an advanced state of saturation, therefore offering
stabilizing bias against inrush effects, but care must be no benefit. Still higher harmonics are of magnitude too
taken to ensure that the current transformers are small to be worth consideration.
sufficiently large so that the harmonics produced by
transient saturation do not delay normal operation of the The percentage of fifth harmonic in the transformer
relay. magnetizing current increases significantly when the
The differential current is passed through a filter which transformer is subjected to a temporary overvoltage
extracts the second harmonic; this component is then condition. Some manufacturers apply a measure of fifth
applied to produce a restraining quantity sufficient to harmonic bias to the relay to restrain operation for this
overcome the operating tendency due to the whole of the condition. Typically, such relays are restrained if he
inrush current which flows in the operating circuit. magnetizing current contains 30% fifth harmonic.
By this means a sensitive and high speed system can be The effects of the excessive flux density produced by the
obtained. With the type DTH relay, a static design a application of an overvoltage is described in Section
setting of 15% is obtained, with an operating time of 45 16.2.8
milliseconds for all fault currents of twice or more times
current rating. Modern alternative to harmonic bias
The relay will restrain when the second harmonic
component exceeds 20% of the current. a). Inrush detection

(c) Third Harmonic another feature that characterizes an inrush current can be
seen from Figure 16.4 where the two waveforms (c) and
The third harmonic is also present in the inrush current in (d) have periods in the cycle where the current is zero.
roughly comparable proportion to the second harmonic. The minimum duration of this zero period is theoretically
The separate phase inrush currents are still related in one quarter of the cycle and is easily detected by a simple
phase to the primary applied electromotive forces and the timer.
harmonics have a similar time spacing, which brings the
third harmonic waves in the three windings into phase. If 1
the windings are connected in delta, the line currents are T1 that is se to seconds. Figure 16.14 shows the
each
4f
……………………………………………………………. circuit in block diagram form. Timer T1 produces an
Components vary during the progress of the transient output only if the current is zero for a time exceeding
condition it is possible for this difference to pass through 1
seconds.It is reset when the instantaneous value of
zero, so that the third harmonic component in the line 4f
current vanishes; this component cannot, therefore, be the differential current exceeds the setting reference.
regarded as a reliable source of bias.
As the zero in the inrush current occurs towards the endo
of the cycle it is necessary to delay operation of the
1
differential relay by seconds to ensure that the zero
f
condition can be detected if present. This is achieved by
using a second time T2 which is held reset by an output
To this must be added the further consideration that a from timer T1 seconds,
sustained third harmonic component is quite likely to be
produced by CT saturation under heavy in-zone fault
conditions.

All this means that the third harmonic is not a desirable

means of stabilizing a protective system against inrush
effects.

(d) higher harmonics timer T2 is held reset and the differential relay which may
be controlled by these times is not permitted to trip. When
All other harmonics are theoretically present in inrush a differential current exceeding the setting of the relay
current but the relative magnitude diminishes rapidly as flows, timer T1 is reset and timer T2 times out to give a
the order of harmonic increases; there may be 5% of 1
fourth harmonic in a given inrush current. This component trim signal in seconds. If the differential current is
f
would be similar in response to the second harmonic but
characteristic of transformer inrush, then timer T2 will be
the small magnitude hardly justifies the provision of an
reset on each cycle and the trip signal is blocked.
extra filter circuit.
307
(b) Transformer over fluxing detection 1000
A current of 0.97A will therefore flow in the relay. If the
When a transformer is subjected to an overvoltage it takes relay has a setting of 25% of 5A, the system will have an
large pulses of current for the portion of each cycle during effective overcurrent setting of
which the instantaneous value of the voltage exceeds the
‘knee’ of the magnetizing curve for the transformer core.
The magnetizing current will therefore, have two periods
1.25
x 100%
in each cycle where the current is below the differential 0.97
setting threshold of the relay as shown in Figure 16.15.
1 that is. 129% of the rated current of the transformer. Thus
typically each of these periods exceeds seconds both differential protection with a nominal setting of 25%
4f and a general overload feature are obtained with the same
duration. relay.
Operation of the relay will therefore be blocked for this
form of magnetizing current. If the need to use current transformers of standard ratios
As the degree of overfluxing increases, the zero gaps causes difficulty in obtaining a desired overcurrent setting,
become shorter. However, a rise in voltage of more than interposing current transformers can be introduced as
40% would be required to reach the point where the gap shown in Figure 16.16 9b).
technique would no longer suffice. A similar performance
would be obtained using fifth harmonic restraint against 16.8……………
overfluxing. However a voltage rise of this order would be
unusual, resulting in an unacceptable degree of Auto-transformers are sometimes used to couple EHV
overfluxing requiring the application of an overfluxing power networks in the ratio of their voltages is moderate.
relay such as the type GTT. Differential protection as described above can be applied
but, as an alternative, protection can be based on the
application of Kirchoff’s law to a conducting network,
namely that the sum of the currents flowing into all
external connections to the network is zero.
A circulating current system is arranged between equal
ratio current transformers in the two groups of line
connections and the neutral end connection. If one neutral
current transformer is used, this and all the line current
transformers can be connected in parallel to a single
Figure 16.15 Magnetizing current during overfluxing element relay thus providing a scheme responsive to earth
condition. faults only, see Figure 16.17 9a).
If current transformers are fitted in each phase at the
The type MBCH relay uses the current zero detection neutral end of the windings and a three element relay is
technique to give consistent operation times for internal used, a differential system can be provided giving full
faults without resorting to large current transformers. protection against phase and earth faults, see Figure 16.17
(b). the relays are of the high impedance instantaneous
16.7.3 unbiased type similar to the single element relays used for
Rough balance scheme restricted earth fault protection.
This protection can be of good sensitivity and the highest
A variation of the simple differential protection provides speed. It is unaffected by ratio changes on the transformer
both differential protection and general system back-up due to tap-changing and is immune to the effects of
and overload protection using only a triple pole I.D.M.T. magnetizing inrush current.
relay, On the debit side, it does not respond to interturn faults a
A normal circulating current system is set up, but the deficiency which is serious in view of the high statistical
ratios of the current transformers are chosen so as to risk quoted in Section 16.2.5. such faults, unless otherwise
depart from the true balance condition by a small amount. cleared will be left to develop into earth faults by which
The relay is a standard I.D.M.T. type having a setting time considerably more damage to the transformer will
above the differential current during full load conditions. have occurred.
In the example illustrated in Figure 16.6 (a) the In addition, this scheme does not respond to any fault in a
transformer is rated at 7.5 MVA. 33kV /11kV connected tertiary winding. Unloaded delta-connected tertiary
delta-stare. Full load currents are 131A and 393A windings are often not protected alternatively the delta
respectively. Current transformers are 150/5A star- winding can be earthed at one point through a current
connected on the 33kV side and 1000/5A or 577/.89A transformer which energizes an instantaneous relay.
delta-connected on the 11kV side. Full load three-phase This system should be separate from the main winding
current will produce outputs from the CT groups as protection. If the tertiary winding earthing lead is
follows: connected to the main winding neutral above the neutral
current transformer in an attempt to make a combined
131 system, there may be ‘blind spots’ which the protection
33kV side: x 5 = 4.37A
150 cannot cover.
308
 DIAGRAM

Figure 16.17 Protection of auto-transformer by high impedance differential relays

309
Diagram

Figure 16.18 Amount of winding protected when

transformer is resistance earthed and ratings of
transformer and resistor are equal.

16.9
COMBINED DIFFERENTIAL AND RESTRICTED One method uses an auxiliary summation current
EARTH FAULT SCHEMES transformer and the other an auxiliary star/delta current
transformer. The latter method is more commonly used as
The advantages to be obtained by the use of restricted it can also provide ratio matching for the differential
earth fault protection, discussed in Section 16.6 lead to protection.
such a system being frequently used in conjunction with
an overall differential system. The importance of this 16.9.1
shown in Figure 16.18 from which it will be seen that if Summation CT Scheme
the neutral of a star-connected winding is earthed through
a resistance of one pair per unit, an overall differential The summation CT, which has four identical primary
system having an effective setting of 20% will detect windings is connected to the main current transformers
faults in only 42% of the winding from the line end. and relays as shown in Figure 16.19.
The requirement for current transformers are quite The current transformers are effectively delta-connected
different in the two systems in that restricted earth fault with respect to the differential system, the circulating bus
…………………… in delta on the star side of the wires receiving the vector difference of pairs of phase
transformer. To provide two sets of current transformers currents.
would be expensive but a single set can be used for both
The summation CT, however, is energized by individually
duties.
phase currents, the total summing to zero in the core for
Two alternative methods are available which will enable a
single set of line current transformers to be used for both balanced conditions. In conjunction with the infeed from
differential protection and restricted earth fault protection the neutral CT, the combination provides a restricted earth
of star windings. fault scheme, responsive only to in-zone residual current.
Thus both the differential and the restricted earth fault
systems operate according to their characteristics.

310
Figure 16.9 combined differential and earth fault protection using summation auxiliary current transformer

When the line current transformers are connected in star have a 2-1-1 pattern of current distribution between the
on the star side of the power transformer as in often phases.
preferred, a star/delta group of auxiliary current When the transformer in question represents a major
transformers can be used to restore correct phase power feed, it may be desired to earth the system at that
conditions for balance. This is shown in Figure 16.20 point, to which end an earthing transformer or earthing
form which it can be seen that is also convenient to reactor connected to the system, frequently close to the to
connect a restricted earth fault relay on the primary side of the main supply transformer and within the transformer
the auxiliary current transformers. protection zone.
Although the earth fault and differential relays in the
above two schemes cover their respective fault conditions, Zero sequence current which flows through the earthing
it must not be thought that their operation is entirely transformer during system earth faults will flow through
independent. The setting and stability conditions for each the line current transformers on this side and without an
must be calculated taking into account all the impedances equivalent current in the balancing current transformers,
introduced into the circuit by the auxiliary current will cause unwanted operation of the relays.
transformers and relays.
Moreover, the condition of the main current transformers The above condition is corrected by subtracting the
during in-zone fault condition is radically different from appropriate component of current from the main CT
their state in the through fault condition. As a result, when output, as shown in Figure16.21. such a current is to be
a heavy inter-phase fault occurs, not only will differential found in the neutral conductor of the earthing transformer
scheme operate but the restricted earth fault relay is also which carries three times the zero sequence component.
quite likely to operate because of spill current. This is no Injection into each phase is required, but usually a single
detriment to the protection, although the unexpected earth CT equal in ration to the line current transformers is
fault indication may confuse subsequent fault analysis. mounted in the neutral circuit. The output of this CT
This is a small price to pay for the saving in current energizes in series three interposing current transformers
transformers which has been achieved. whose ration is //0.333; the latter transformers are
arranged to subtract their output from that of the line
16.9.3 current transformers in each phase, thereby cancelling the
Combined differential and REF protection when zero sequence component and restoring balance to the
earthing transformers is connected within the differential system.
protected zone
A high impedance relay can be connected in the neutral
A delta-connected winding cannot deliver any lead between current transformers and differential relays
zero……………………………………………………….. to provide restricted earth fault protection.
or an earthed neutral elsewhere on the system and will
As an alternative to the above scheme, the circulating
current system can be completed via a three –phase group

311
Figure 16.20 Combined differential and restricted earth fault protection

Figure 16.21 Differential protection with in-zone earthing transformer with restricted earth fault relay.

Figure 16.22 Differential protection with in-zone transformer no earth fault relay

of interposing transformers which are provided with

tertiary windings connected in delta. This winding provided restricted earth fault protection is not required,
effectually short-circuits the zero sequence component the scheme shown in Figure 16.22 has the advantage of
and thereby removes it from the balancing quantities in not requiring a current transformer , with its associated
the relay circuit; see Figure 16.22. mounting and cabling requirements, in the neutral-earth
312
conductor. Alternatively the scheme can be connected as
shown in Figure 16.23 when restricted earth fault The schemes described in the foregoing section refer to an
protection is needed. earthing transformer connected within the zone of
protection for the main transformer.
16.10

Figure 16.23 Differential protection with in-zone earthing transformer with alternative arrangement of restricted earth fault
relay

operating conditions which are attribute to errors in

operation.
The condition does not call for high speed tripping
instantaneous operation is undesirable as this would cause
tripping on momentary system disturbances which can be
borne safely, but normal conditions must be restored or
the transformer must be isolated within one or two
minutes at most. The fundamental equation for the
generation of e.m.f. in a transformer can be arranged to
give:
E
Φ=K ( )
f
Figure 16.24 Earthing transformer protection It is necessary to detect a ration of E/f exceeding unity, E
and f being expressed in per unit values of rated
When it is not so located it also requires protection, which quantities. The system voltage as measured by a voltage
is arranged as shown in Figure 16.24. the delta-connected transformer is applied to a resistance to produce a
current transformers are connected to three I.D.M.T. proportionate current; this current on being passed
overcurrent relays. The normal action of the earthing through a capacitor produces a voltage drop which is
transformers is to pass zero sequence current. The proportional to the function in question, E/f and hence to
transformed equivalent current circulates in the delta the flux in the power transformer. Feedback techniques
formed by the CT secondaries without energizing the are used in the type GTT relay to make the measured ratio
relays. The latter may therefore be set to give fast and accurate over a wide range of frequency and voltage.
sensitive protection against faults in the earthing Two time delay outputs are given by auxiliary elements,
transformers itself. each with multiple contacts. One element, the contacts of
which are used to effect a control operation to rectify the
16.11 abnormal condition, operates after a pre-selected fixed
……………………………………… time delay between 0.5s and 1.0s or between 2s an d5s.
the second element is arranged to trip the supplies to the
The effects of excessive flux density are described in transformer after a pre-set time delay of 5s to 30s or 12s to
Section 16.2.8. the condition arises only from abnormal 120s if the abnormal condition persists.

313
Overfluxing protection is mostly confined to generator The device is commonly fitted to power transformer, rated
transformers for which the risks appear to be greatest, at 2 MVA or higher, but may be applied to distribution
although overfluxing trouble has been known to occur for transformers rated as low as 200 kVA, particularly those
other transformers as well. in hazardous areas.

16.12 16.13.2
TANK EARTH PROTECTION Rapid pressure rise delay
This is also known as Howard protection. If the
transformer tank is nominally insulated from earth (an This device detects rapid rise of pressure rather than
insulation resistance of 10ohms being sufficient) earth absolute pressure and thereby can respond even quicker
fault protection can be provided by connecting a relay to than solute pressure and thereby can respond even quicker
the secondary of a current transformer the primary of than the pressure relief valve to sudden abnormally high
which is connected between the tank and the earth. This pressures. Sensitivities as low as 1p.s.i./sec are attainable,
scheme is similar to the frame-earth fault busbar but when operating in oil the operating speed of the device
protection described in Section 15.5. may have to be slowed deliberately to avoid spurious
tripping during circulation pump starts.
OILAND GAS DEVICES
All faults below oil in a transformer result in the localized 16.13.3
heating and breakdown of the oil; some degree of arcing Buchholz protection
will always take place in a winding fault and the resulting
decomposition of the oil will release gases such as The Buccholz relay is contained in a cast housing which is
hydrogen, carbon monoxide and light hydrocarbons. connected in the pipe to the conservator, as in Figure
When the fault is of a very minor type, such as a hot joint 16.25.
gas is released slowly but a major fault involving severe
arcing causing rapid release of large volumes of gas as
well as oil vapour. The action is so violent that the gas and
vapour do not have time to escape but instead build up
pressure and bodily displace the oil.
When such faults occur in transformers having oil
conservators, the fault causes a blast of oil to pass up the
relief pipe to the conservator.
Recognition of the above action by Buchholz and the
limitations of other means of detecting certain types of
fault, led to the development of the protective device TRANSFORMER
generally known by his name. Figure 16.25 Buccholz relay mounting arrangement
Devices responding to abnormally high oil pressure or
rate-of-rise of oil pressure are also available and may be A typical Buccholz relay comprises two pivoted
used in conjunction with a Buchholz relay. aluminum floats or buckets, each counterbalanced so that
with this device empty or completely full of oil the bucket
16.13.1 or float in a high position. Each pivoted bucket assembly
Oil pressure relief devices carries mercury switch; see Figure 16.21.
In the normal condition the casing is filled with oil, so that
The simplest form of pressure relief device is the widely the bucket floats are high and the mercury switches and
used ‘frangible disc’ which is normally located at the end open. If gas bubbles pass up the piping., they will be
of an oil relief pipe protruding from the top of the trapped in the relay casing, so displacing oil. As the oil
transformer tank. lever falls the upper float will follow, since the weight of
The surge of oil caused by a serious fault bursts the disc, the bucket filled with oil exceeds that of the
so allowing the oil to discharge rapidly. By relieving and counterbalance when the buoyancy form the surrounding
limiting the pressure rise, explosive rupture of the tank oil is lost. Ta the float falls, the mercury switch tilts and
and consequent fire risk is avoided. closes and alarm circuit.
A drawback of the frangible disc is that the oil remaining A similar operation will occur if a tank leak causes the
in the tank is left exposed to the atmosphere after rupture. ….level to fall.
This is avoided in a more effective device, the sudden The device will therefore give an alarm for the following
pressure relief valve, which opens to allow discharge of fault condition, all of which are of a low order of urgency:
oil if the pressure exceeds about 10 p.s.i., but closes a) Hot spots on the core due to short circuit of
automatically as soon as the internal pressure falls below lamination insulation.
the critical level. b) Core bolt insulation failure.
If the abnormal pressure is relatively high, this spring- c) Faulty joints.
controlled valve can operate within a few milliseconds, d) Interturn faults or other winding faults involving
and provide fast tripping when suitable contacts are fitted. on lower power infeeds.
Where it is considered essential to avoid the random e) Loss of oil due to leakage.
discharge of oil into the area surrounding the transformer, When a major winding fault occurs, this causes a surge oil
the discharge of oil may be ducted to a catchment pit. which displaces the lower float and thus isolates the
transformer. This action will take place for;
314
 (i) All severe winding faults, either to earth or
interphase.
(ii) Loss of oil if allowed to continue to a dangerous
degree.

The relay is usually provided with an inspection window

on either side of the gas collection space, through which
the oil level can be observed. This may help in diagnosis
the fault. For example, if the gas is white or yellow, +
insulation has been burnt, while if it is black or grey,
dissociate oil is indicated. In these cases, the gas will
probably be inflammable, whereas released air will not. A
petcock provided on the top of the housing for the gas to
be released. If necessary, it can be drawn off and collected
in analysis, using a piece of rubber tubing fitted over the Figure 16.26 Typical transformer-feeder circuits.
release nozzle.
When mounting the relay, it is essential to ensure that they The saving in switchgear so achieved is offset by
will pass freely up the pipework and also that extra to increased complication in the necessary protection. The
balance is not induced in the oil steam. The relay should primary requirement is intertripping, since the feeder
be mounted with the arrow on the casing pointing to the protection remote from the transformer will not respond to
conservator, in a straight run of pipe which should slowly the low current fault condition which can be detected by
upward from the transformer to the conservator at an and restricted earth fault and Buccholz protections.
of 5 degrees. To avoid turbulence which would alter the Either unrestricted or restricted protection can be applied;
effective sensitivity in terms of oil velocity, the pipe moreover, the transformer-feeder can be protected as a
should ………. single zone or be provided with separate protections for
Particularly with larger transformers having separate the feeder and the transformer. In the latter case, the
radiators and forced circulation, surges of oil pressure on separate protections can both be unit type systems. An
starting the pumps cause expansion of the radiator tubes, alternative, ………………………………. feeder
leading to a flow of oil in the conservator pipe. The protection, plus an intertripping feature.
Buchholz relay must not operate in this circumstance.
When the oil is being cleaned by circulation through 16.14.1
centrifuging or filtering plant as part of routine Non-unit schemes
maintenance, aeration takes place, with the result that air
is released and collected in the Buccholz relay. It is Feeder phase and earth faults
therefore necessary to disconnect the tripping circuit, High speed protection against phase and earth faults can
leaving the alarm function only, while the oil being treated be provided by distance relays located at the end of the
and for alarm function only, while the oil is being treated feeder remote from the transformer. The first zone of a
and for about 48 hours afterwards. During this period, distance scheme applied to a simple feeder would be set to
discretion must be used when dealing with alarm signals. reach only 80-85% of the feeder length, the margin being
Because of its universal response to faults within the to allow for various errors in measurement. In the case of
transformer, some of which are difficult to detect by other a transformer-feeder, the transformer constitutes an
means, the Buchholz relay in invaluable, whether appreciable lumped impedance. It is therefore possible to
regarded as a main protection or as a supplement to other set a distance relay zone to cover the whole feeder and
protection schemes. Tests carried out with simulated reach part way into the transformer impedance. With a
operating conditions, that is, by striking a high voltage arc normal tolerance on setting thus allowed for, it is possible
in a transformer tank filled with oil, have shown that for fast zone 1 protection to cover the whole of the feeder
operation in the time range 0.05-0.1s is possible. with certainty without risk of over-reaching to a fault on
Electrical protection is generally used as well, either to the low voltage side.
obtain in faster operation for heavy faults, or because Although the distance zone is described as being set ‘half
Buchholz relays have to be prevented from tripping during way into the transformer’, it must not be thought that half
oil maintenance period. Nevertheless, Buchholz relays are the transformer winding will be protected. The effects of
included in the protection schemes of all transformer fitted auto-transformer action and variations in the effective
with conservators, in British and European practice. impedance of the winding with fault position prevent this,
Transformers without conservators (usually of less than making the amount of winding beyond the terminals
1000 kVA rating) cannot be provided Buchholz which is protected very small. The value of the system is
protection. confined to the feeder which as stated above, receives
high speed protection throughout.
16.14
A transformer-feeder comprises a transformer directly Feeder phase faults
connected to a transmission circuit without the A distance scheme is not, for all practical purposes,
intervention of switchgear. Examples are shown in Figure affected by varying fault levels on the high voltage
16.26 busbars and is therefore the best scheme to apply if the
fault level may vary widely. In cases where the fault level

315
is reasonably instantaneous overcurrent relays, provided
these have a low transient over-reach.
Transient over-reach is defined as:
Iₛ−If
x 100%
If
Where; I = setting, that is r.m.s. value of steady state
current required to operate the relay.

If = steady state r.m.s. value of the fault current

which when fully offset will just operate the
relay.

The instantaneous overcurrent relays must be set without

risk of them operating for faults on the remote side of the
transformer.
Referring to Figure 16.27, the required setting to ensure
that the relay will not operate for a fully offset fault I f2 is
given by.

Is = 1.2 (1+t) If2

Where If2 is the fault current under maximum source
conditions, that is when Zs is minimum, and the factor of
1.2 covers possible errors in the system impedance details
used for calculation of If2 together with relay and CT
errors.
As it is desirable for the instantaneous overcurrent
protection to clear all phase faults anywhere within the
feeder under varying system operating conditions, it is
necessary to have a relay setting less than If1 in order to
ensure fast and reliable operation.
Let the setting ration resulting from setting I, be

Is
r=
If1

OVERCURRENT PROTECTION FUNDAMENTALS

FOR OVERHEAD DISTRIBUTION

Extensive studies of overhead distribution systems throughout the world, have established that
up to 95% of all short circuits, of faults, are temporarily in nature, lasting only few cycles to a
few seconds at the most.

Typical cause of these temporary faults are:

1) Windblown conductors touching one another.
2) Lightning surges flashing over an insulator.
3) Birds, reptiles or small animals contacting between an energized line and a grounded
surface.
4) Tree branches touching against, or being blown across energized lines.

316
 5) Switching surges. Although such overcurrent conditions are not faults, they are
temporary and can cause fuses to operate.

Based on these statistics and observations, the need for a “trip and reclose” function was
readily recognized. That is, if the line could be tripped open and the fault cleared, reclosing a
few cycles later would be successful because the cause of the fault would then have
disappeared. Of course, this trip-recloser function should be done automatically.

AUTOMATIC CICUIT RECLOSER

The “automatic circuit recloser” has proved to be the ideal device for virtually eliminating
prolonged outages on distribution systems due to temporary faults or transient overcurrent
conditions.

Automatic circuit reclosers provide continuity electric service simply, reliably and
economically.
Diagram

The automatic circuit recloser is a fault interrupting device (i.e. kind of breaker) with
intelligence. It may be single phase or three phase, and the interrupters are contained in an oil-
filled tank, or air-filled tank in the case of vacuum reclosers. In appearance it resembles a small
bulk oil circuit breaker and it can be direct pole mounted, crossarm mounted platform mounted
or installed in a substation frame.

This is how an automatic circuit recloser operates:

The recloser senses an overcurrent condition, interrupts current flow and then, after a
predetermine time delay reclosed automatically to re-energize the line. If the fault is still
present, the recloser repeats this trip-reclose sequence up to three times. After the fourth trip
operation it locks itself open.
Diagram

Fig No 13: Typical recloser operating sequence

317
This repetitive trip-reclose sequence with ultimate lockout accomplishes two important
functions:
1) The recloser repeatedly “tests” the line to determine if the fault condition has
disappeared.
2) The recloser can discriminated between temporary and permanent faults. If, after three
“tests” the fault condition is still present, it can be assumed that the fault condition is
still present, it can be assumed that the fault is permanent and the reclose locks out.

The following table of actual fault experience for a none-year period on a typical distribution
system properly protected by reclosers is quite impressive.

FAULTS EXPERIENCE SUCCESSFUL RECLOSER PERCENT OF TOTAL

896 First 88.7
46 Second 4.5
13 Third 1.3
55 Lockout 5.5
1010 100.0%

Analysis of tis table shows that 88.7% of all faults occurring on the system during the period of
study were cleared by the first trip-recloser sequence of a recloser. The use of reclosers
eliminated 896 prolonged outages and service calls, which would have been required if the
circuits were only protected with fuses, as they should have been then replaced by the
linesman.

After three trip-recloser sequences, another 5.8% of all faults were cleared, making a grand
total of 94.5% or 955 outages and service calls that were eliminated. The very significant cost
saving in serving and manpower involved for power supply restoration needed is obvious.

Only the remaining 5.5% of the total number of faults can be assumed to have been permanent
and would, in any case, have required a service crew to correct the cause, e.g. broken lines or
poles, obstacles on the line, failed equipment etc.

AUTOMATIC LINE SECTIONALIZER

Another overcurrent protection device, which was designed to serve in conjunction with the
automatic circuit recloser is the “automatic line sectionalizer”. It is basically an oil-filled
switch of either single-phase or three-phase design and closely resembles a recloser in outward
appearances.

318
Fig No. 14 Automatic Line Sectionalisers

The sectionalizer, however, does not interrupt fault current. It is located in series with, and at a
remote distance from, a recloser on the load side of a recloser. It counts each time the recloser
interrupts fault current and after a predetermined number of interruptions by the recloser, one,
two or three, it opens its contacts – always on a dead circuit. There is no electrical or
mechanical interconnection between recloser and sectionalizer. In this manner, a permanently
faulted section of line can be isolated without causing a recloser to operate to lockout, thus
preventing a total power supply outage in the entire line and giving a better indication on
where exactly the permanent fault occurred.

Although the sectionaliser does not interrupt fault current, it can interrupt full normal load
current and can therefore be used as a load break switch for manual line sectionalizing.

Overcurrent Protection Fundamentals

As an overcurrent protection scheme develops, several factors dictate the use of different types
of protective devices, in series. This study of the correct application of protective devices in
series is called “coordination”.

By common definition, when two or more protective devices are applied to a system, the
device nearer the fault (on the source side of the fault) is the “remote” or “protection” device.
The adjacent device nearer the source is the “back up” or “protected”

Fig No. 15: Protective devices, depending on location in a system, are designated as backup or
protected remote or protecting.

Two coordination principles must also be considered:

1. The protecting (remote) device must clear a permanent or temporary fault before the
protected (back-up) device interrupts the circuit (as in the case of a fuse link) or
operates to lockout (as in the case of a recloser).
2. Outages caused by permanent faults must be restricted ot the smallest possible section
of the system for the shortest possible time.

The first major decision in applying overcurrent protective devices on overhead distribution
lines is to determine the appropriate physical locations. One obvious location is at the source of
a feeder. In this way the feeder is isolated in case of a permanent fault at the substation. Then,
upon individual system conditions, additional devices may be located in series on the feeder at
logical sectionalizing points to restrict any outage to the smallest practical segment of the
system.
319
In Fig. No. 16, we can see a typical example of selection and locations of protective
equipment.

Fig No. 16: Typical locations for protective equipment

As a rule of Thumb, the following must be considered.

Possible locations for recloser are:

1. In substations as the primary feeder protective device.
2. On the lines at a distance from substation, to sectionalize lon feeders and thus prevent
outages of the entire feeder for a permanent fault occurring near the end of the feeder.
3. On important taps of main feeders to protect the main feeder from interruptions and
outages due to faults on the taps.

For sectionalizers:

320
 1. At branched of big load in series with a back-up recloser.
2. Between two protective devices (reclosers) on a main feeder for more fine
sectionalizing.

For fusing equipment:

1. At the M.T. side of M.T. /L.T. distribution transformers.

2. On branches of small load.

TIME CURRENT CURVES - OPERATING SEQUENCES

Application of protective equipment requires knowledge of ratings time-current curves,

operating sequences and some other basic rules.

Each overcurrent protective device has time-current characteristic curves, which are a plot of
operating time versus current. E.g. a conventional fuse has a minimum melting curve and a
maximum clearing curve associated with each fuse type and rating, as shown in Fig No. 17

Figure No. 17: Typical time-current curves for a 10K fuse link

An automatic circuit recloser usually has a family of time –current characteristic curves; a fast
curve which has little or no intentional time delay; and a group of delayed curves, which are
required for satisfactory coordination with other protective devices in series. See Fig NO. 18.

The selection of the combination of time-current curves (A, B, or C) according to which a

recloser fall sequently operate under fault conditions, will provide a variety of coordination
schemes with other protective devices.

321
Fig No. 18: Typical ABC curves for 50-ampere, single-phase recloser.

After preliminary decisions regarding desired physical locations the following major factors
must be given consideration for a good overcurrent protection scheme.

A RECLOSERS
1. Phase-to-phase voltage should not exceed design voltage of the recloser.
2. Continuous current rating of the recloser should be equal to or greater than maximum
load current through the recloser.
3. Interrupting rating of the recloser should be equal or greater than maximum available
fault current at the recloser location.
4. Minimum trip current selected should permit the recloser to sense fault current
throughout the desired protection zone.
5. Time-current curves and operating sequences selected should allow coordination with
other protective devices on both sides of the recloser

B SECTIONALIZERS
1. Sectionalizer must be used in series with and on the load side of an automatic circuit
recloser.
2. The backup recloser must be capable of sensing a minimum fault throughout the
sectionalizer protection zone.
3. Minimum fault current in the protection zone must exceed sectionalizer minimum
actuating current.
4. Momentary and short-time ratings of the sectionalizers must not be exceed.
5. The sectionalizer should be set to lockout in one less operation than the backup device.
322
C FUSING EQUIPMENT
1. For all values of fault current possible on the section protected the fuse link, the
minimum melting time of the link must be greater than the clearing time of the fast,
operation of the backup protective device.
2. For all values of fault current possible on the section protected by the fuse link, the
maximum clearing time of the fuse should be no greater than the delayed clearing time
of the backup protective device.

Considering possible combination, the following distinct types of coordination involving

automatic circuit reclosers can be identified:

1. Recloser - Recloser
2. Recloser - Sectionalizer
3. Recloser - Fuse link
4. Recloser - Sectionalizer – Fuse link
5. Breaker Recloser

We will see how these coordination schemes can be achieved by examining more thoroughly
the two first options.

Recloser / Recloser coordination

To coordinate reclosers it is necessary to study time-current characteristic curves of the

devices.

Time-current curves can be selected so that the recloser will operate firstly on a fast time-
current curve followed by operation on delayed curve (see Fig No 19).
A fast curve. B = delayed curve and C = extra delayed curve.

Fig No. 19 : Typical ABC curves for 50-ampere single-phase recloser

Fig No. 20 shows an example where all reclosers have 100-Amp coils, but ACR2 is set for
2ABC sequence while ACR2 and ACR3 are set on 2A2B sequence.
323
Fig No 20: Recloser coordination by means of operating sequence selection.

Should a fault occur at point F, CR1 an ACR2 simultaneously perform one fast operation. This
response is expected because both reclosers are operating on the same time current curve. The
ACR2 on the 2A2B sequence then completes its second fast operation before ACR1 can
operate on its delayed C curve. If the fault is permanent, ACR2 operates to lockout because
ACR2 operates on the B curve faster than ACR1 operates on the C curve. With this method,
the branch line fault causes one brief interruption of loads along the primary feeder. For a
permanent fault at F, only ACR2 will lock out. ACR1 will lock out only for a permanent fault
on the primary feeder such as at K.

Recloser / Sectionalizer Coordination

Because sectionalizer do not have time-current curves as reclosers do, their coordination does
not require a study of curves. A typical application is shown in Fig No. 21

Fig No. 21: Basic recloser – sectionalizer coordination.

The backup recloser is set for four shots to lockout. These operations may be any combination
of fast followed by delayed counts than the backup recloser – in this case three counts are
selected. If a permanent fault occurs beyond the sectionalizer, the sectionalizer will open and
isolate the fault during the third reclosing time of the recloser. The recloser then re-energizes

324
the unfluted sections. If additional sectionalisers are added in series, they can be set for fewer
counts to lockout, as shown in Fig No 22.

Figure No 22: Sectionalizers added to branch lines.

A fault beyond the last sectionalizer actuates the recloser and all three sectionalizers count the
current interruption. Sectionalizer C however, locks out to isolate the faulted branch. The
recloser re-energizes the unfaulted lines, sectionalizers A and B then reset.

………………… AND CONCLUSION

Automatic circuit reclosers can eliminate up to approximately 95% of outages on overhead

distribution systems.

Recloser will coordinate closely and reliably with each other and with other protective devices
(breakers, sectionalizers and fuse cutouts). They automatically isolate permanently faulted
sections of line and are readily applicable in remote manual or supervisory controlled schemes.

Fig No 23 Fig No. 24

Pole-mounted 3-phase recloser Pole-mounted single-phase reclosers

In addition, reclosers and sectionalizers are extremely durable and reliable devices that will
serve for many years. They have long operating duty cycles and require almost no
maintenance. This means continuous power supply to customers i.e. increased reliability and
greatly reduced service costs.

325
 EXAMPLE OF RURAL ELECTRIFICATION WITH

THE “LONG FEEDER” APPROACH

To visualize how rural electrification scheme could be developed with the “long Feeder’
approach, we have defined a typical rural are of 150km radius, as shown in Fig. No 25a, to be
electrified. This area will be served with 12 main long feeders and we will see how all the
possible problems discussed before, are confronted.

Each feeder will serve a part of the whole area (Fig No. 25b). the RCAP computer program
was used for determining the number of regulators and capacitor banks needed to have
acceptable voltage levels through all the feeders (main and secondary) in the system and the
nodes at which these devices should be installed. The V-PRO computer program was used for
determining sectionalisers needed to protect the feeder from overcurrent conditions and
improve system reliability.

The electrification scheme was developed in 3 steps. Step No. 1 (or case “Base”) is considered
in Fig No 26a, b and c. table No 1 capacitor banks, voltage regulators and voltage profile of
main step No2 (or case S1) is considered in Fig 27a, b and c and comes out from case “Base”.
In this Step we have load increase 2 arrows at the corresponding nodes of Fig 27c) and a line
extension from rode 39 to node 43 (dashed line), to serve a new customer.

Table No. 2 indicates the relevant computer outprints for case S1. In step No 3 (or case S2), we
have a further load increase shown again with “shadowed” customers in Fig No 28a and with
double arrows in Fig No 28c.

Table No 3 indicated the computer outprints for case S2. Through this procedure we could
electrify the whole area (all the villages not yet connected with the long feeder, Fig 28a) with
the only restriction of the thermal limit of the used conductors.

Table No.4 refers to the overcurrent protection scheme of the said feeder and is applicable to
all three cases without any change. If at a future case there is a substantial change of the rated
current and the fault levels of the feeder, a change of coil sizes could simply adjust this
overcurrent protection scheme to the new existing conditions.

326
LOW-OIL-CONTENT CIRCUIT BREAKERS

Types ORI/ORE 17,24 & 36

Instruction 65E1

LOW-OIL-CONTENT CIRCUIT BREAKERS

327
 Types ORI/ORE 17, 24 & 36

Types ORI and ORE circuit breakers have independent single-phase units or poles mounted on
a common base, each made up of a vertical bushing.

The bushing is closed at the bottom by a case secured to the C. B. base box and containing the
shaft and the operating crank of the moving contact.

The lower half of the bushing acts as an insulating support for the live parts: lower and upper
stationary contacts, moving contact, expansion chamber.

The interrupting chamber, placed in the upper part of the bushing between upper and lower
contacts, is made up of a pile of insulating washers having a shape apt to facilitate the arc
interruption at each breaker tripping under load.

The three C.B poles are mounted on the common base by two Z- shaped angle irons and are
secured by two simple screws. A single connection rod joins the external cranks of the three
poles to the C.B. drive shaft. The operating mechanism is fixed to the front side of the base box
by a simple flange. Both the poles and the operating mechanism can therefore be independently
removed and replaced.

The energy required for breaker tripping can be delivered by a set of springs contained in the
base box. In this case the operating mechanism must provide a closing torque capable of
simultaneously charging also the opening springs.

When, on the other hand, operating mechanisms of the MACI line are used, the opening
springs are not contained in the C.B. base box but, together with the closing springs, in the
operating mechanism itself, which charges them before each closing operation, and then couple
them to the circuit breaker only when the latter has completed the closing operation.

Circuit breakers for both indoor (ORI type) and outdoor (ORE type) installation are produced
for the maximum voltage service of 17,24 and 36kV and for the rated currents of 400 and 630
A. they are shipped with the poles already mounted on the base box.

INSTALLATION

Remove the circuit breaker from the crate or case in which it was shipped, place it on the
supporting structure and fix its base with 12mm diam bolts.

If the circuit breaker is not already full of oil, unscrew the covers closing the expansion
chambers and pour insulating oil having characteristics according to standards, till its level
settles in the middle of the oil gauge existing on each expansion chamber. Then screw the
covers again.

328
Connect the base box to earth.

Apply the operating mechanism and carry out the wiring indicated in the diagram supplied
with the circuit breaker. Finally perform some closing and opening operations.

Check the oil level and add oil fi necessary.

Carefully connect the high voltage conductors to the terminals of each pole so as to ensure a
good contact.

MAINTANANCE

Before starting any maintenance work the circuit breaker must be de-energized, placed in the
open position and connected to earth. If it is mechanically-operated, the operating mechanism
must be de-energized.

Keep clean and well lubricated the hooks and pivots of the operating mechanism, keep clean
the position indicating contacts. Remove, with the help of a clean and dry rag, the dust
accumulated on the external surface of the insulators.

Insulating oil
Make sure that the oil is always visible through the gauge glass provided on the expansion
chamber of each pole.

The darkening that can be noticed in the oil after the interruption of even only a few faults does
not indicate a great deterioration of the dielectric properties, nor inability to secure the full
interrupting capacity, and therefore it should not be taken as a reliable indication on which to
base a maintenance programme.

The oil must be replaced even for one only of the following reasons:
a) The break-down voltage measured between 10 mm diam. Spheres 5mm apart has been
found less than 40kV;
b) The circuit breaker has performed opening operations for a total amounting to 200 kA.

When changing the oil, and after draining the old one, it is well to flush the poles with new oil
before filling them again.

In case of oil leaks along the drive shaft of a pole, drain the oil, remove the pole and place it
horizontally with the shaft downwards. Then remove the screws fixing the bronze sleeve to the
ploe lower case and take out the bronze sleeve as well as the shaft by levering, with the help of
two screwdrivers inserted in two diametrically opposed points, between sleeve and case.
Before changing the rings make sure that the shaft is perfectly smooth and cylindrical, as
scores or unevenness would cause leaks even with new rings.

Breaking contacts
329
The loss of material suffered by the contacts at every load interruption is proportional to the
product of the intensity of the interrupted current by the coefficient ∝ given in the diagram
included in this booklet. If therefore the circuit breaker is called upon to open currents of
always the same intensity, the date at which the contacts are to be replaced may be expressed
by the maximum number of tripping operations allowed for that particular value of the current
involved (see curve ‘n” plotted in the diagram for the contact maintenance included in this
booklet).

When on the contrary, and this occurs more frequently , the circuit breaker is called upon to
clear currents of different intensity, the contacts wear must be assessed in kA by performing
the summation of the intensities of the currents interrupted at each tripping, each multiplied by
the corresponding coefficient ∝.

The breaking contacts must be replaced when the summation reaches the maximum value T
quoted, for each type of circuit breaker, on the diagram for contact maintenance included in
this booklet.

Replace the contacts as follows:

1. Separate the H.V. conductors, drain the oil contained in the poles, remove the
connecting rod between the poles, then remove the poles from the supporting angle
irons and place them horizontally.

2. Remove the expansion chamber, the corresponding gaskets and the baffles 3 fig. 2.

3. Unscrew the supports of the upper stationary contacts, along with the copper blades, the
leaf springs and the protection plates.

4. Remove the lower cases of the poles and replace the moving contacts.

5. Reassemble the poles, having first carefully cleaned the slots intended to contain the
gaskets and replaced the latter.

INSULATION OIL
330
Producer . . . . . . …………………………………………… ……………. FINA
Type ………………………………………………………………………..FINA DIEKAN
BETA

SPECIFICATIONS
ASTM CET
Density at 15℃ …………………………………………………………. - 0.887
Density at 59℉ ……………………………………………………………. 0.887 -
1
Colour……………………………………………………………………… 1:
ᴥ
golden

Yellow
Reaction …………………………………………………………………… neutral
neutral
Neutralization number (in oleic acid) …………………………………… 0.015 0.015
Free Sulphur corrosive compound…………………………………………. None none
Flash point ……………………………………………………………….. 300℉
149℃
Viscosity at 100℉ (37.78℃) (Engler)…………………………………… - 1.998
Viscosity at 100℉ (Saybolt)……………………………………………… 64 sec. -
Pour point ………………………………………………………………… -40℉ -
Fluency at -20℃ ………………………………………………………….. - ¿18
sec

VISCOUS OIL

Producer …………………………………………………………………REINACH
OLEOBLITZ
TYPE …………………………………………………………………… T. 28

SPECIFICATIONS
ASTM CEI
Density at 15℃ ………………………………………………………….. - 0.91
Density at 59℉…………………………………………………………… 0.91 -

331
Viscosity at 50℃ (Engler) ………………………………………………. - 25
÷ 30
Viscosity at 100℉ (Sayboolt) …………………………………………… 877.8 sec
-
Flash point………………………………………………………………. 530℉
270℃
Mineral acidity (oleic acid) …………………………………………….. Less than Less
than
0.03%
0.03%
Saponification number ………………………………………………….. Less than Less
than
0.3% 0.3%

Figures 1 & 2: External view and cross section view of a pole

1. Filler plug with vent. 2. Expansion chamber.

3. Baffle. 4. Gauge glass with flange and gasket.
5. Gasket for Chamber 2. 6. Stationery contact support.
7. Top Terminal. 8. Metallic sleeve.
9. Top flange. 10. Gasket for supper end of sleeve 23.
11. Gasket between flange 9 and 12. Pole assembly screw.
sleeve 23.
13. Sector for upper stationery contact 14. Set of washers for interrupting chamber
with copper blade.
15. Gap filled with viscous oil. 16. Cylindrical spring for lower stationery
contact.
17. Lower stationary contact. 18. Sleeve with insulating bushing for guide
of
moving contact.
19. Lower terminal with nuts, washers 20. Screw for fixing sleeve 18, with gasket.
And gaskets
21. Intermediate flange. 22. Gasket for insulator.
23. Insulating sleeve. 24. Insulator for indoor.
25. Insulator for outdoor. 26. Moving contact
27. Pivot with two split pins. 28. Lower flange
29. Insulating rod 30. Gasket
31. Case 32. Internal crank.
33. External crank with pin 34. Pivot, with two split pins.
35. Drive shaft. 36. Bronze sleeve with screws.
37. Sealing rings 38. Drain plug with gasket.

332
DIAGRAM

333
Fig 1 Fig 2

Figure 3. Base box (Not used when the three C.B. poles are mounted direct on the
housing of type MACIS operating mechanisms).

1. C.B. base box 2. Z—shaped angle iron for fixing the poles
3. Pole fixing nut. 4. Bronze sleeve for shat 5.
5. Transmission shaft. 6. Opening spring.
7. Pole connecting rod 8. C.B. operating crank with key and pin.

334
Fig 3.

n = maximum number as a function of the interrupted current (supposed to be constant) of the

tripping operations that can be performed without causing over temperatures exceeding
the limits allowed by CEI Standards (diagram US 5489/A)

3 kA
ORI / ORE 17 6 trippings at 9.5 kA
Circuit breakers 45 ʺ ʺ
500 ʺ ʺ 0.5 kA

7.5 kA
2.5 kA
ORI/ORE 24 6 ʺ ʺ

0.5 kA
Circuit breakers 40 ʺ ʺ
350 ʺ ʺ

5.8 kA
7.5 kA
ORI/ORE 36 6 ʺ ʺ

300 7.5 kA
Circuit breakers 35 ʺ ʺ
ʺ ʺ

… = severity factor of each tripping as a function of the interrupted current.

T = Σ∝ I = maximum value allowable for the summation, obtained by multiplying the

intensity of each interrupted current by the relevant ∝ factor.

Once value T is reached, the breaking contacts must be replaced.

..TE: if the values of the currents interrupted at each breaker tripping are not known and the
short circuits are not very frequent, multiply the number of tripping operations by the

335
 value of the average load current circulating through the circuit breaker, and replace the
contacts when this product reaches 60% of the kA indicated in the enclosed diagram.

Diagram

336
Diagram

337
 L1

LINE DROP COMPENSATION

Automatic voltage control for On-Load-Tap-Changers (OLTC) is achieved by two elements: -

(i) Voltage Regulating Relay – operates time delayed RAISE and LOWER contacts
against a pre-set voltage reference. (i.e. by itself will say maintain the voltage on the
11kV bars at 11,8 kV as long as the received voltage is within the tapping range of the
transformer).

(ii) Line Drop Compensating Unit (LDC) - Injects opposing voltages into the AVE
voltage reference circuit, such that the AVE “sees” the apparent received end voltage.

The LDC has three setting potentiometers R, X and Zero. The R and X elements are set
to approximate the resistance and reactance of the line concerned to give a steady state
voltage at a known point on the system known as the “horizon”. The ZERO setting
establishes the voltage reference for the AVE relay. This seems fairly simple. However,
in practice theoretical settings of LDC units are fraught with difficulties.

L2

Consider the following simple system

338
If we set R and X equal to R 1 and X1 respectively we will achieve our horizon or stable voltage
at point “H”.

L3

If we were to set R = R1 + R2 and X = X1 + X2 the horizon would be set at the end of the line.

CHOOSING THE HORIZON

The horizon should be chosen to be an area of highest load density, as position “h” in our
example. However, considering the Commission’s rural lines, this is sometimes difficult if not
impossible to determine, in which case ½ to 2/3 of the feeder length should be chosen.

However, our substations do not consist of one transformer and one feeder. Two transformers
operating in parallel have the disadvantage that the “Master LDC” only sees half of the total
load current. With several outgoing lines the load current seen by the LDC will be the sum of
all the feeder currents. Each feeder may be of different conductor size, (rare) different length
and have different loading cycles.

L4

HOW DO WE SET L.D.C. UNITS

(i) The “useful data” on the back of the first page of the Standard Commissioning
Programme” lists the ratio of r to x for various sizes of standard conductor.
(ii) The L.D.C. setting ranges can be in ohms (0-10), or in percent.

Ascertain the length of the feeder and select suitable settings, maintaining the ratio of r to x
dependent on the majority conductor size.

(Long lines 30-50 km set at maximum)

339
 (Medium lines 20-30 km set at half range etc)

Ask District Staff to install voltage recording instrument at the closest and furthest
substations to observe the voltage variations.

L5

THEORY OF L.D.C.

1) Settings:

This varies from one manufacturer to another, as several different schemes used to
achieve the “dummy line” voltage.

a) English Electric Transformers - use two CTs cross connected feeding directly
into the LDC unit.

K₂
Here r= R
K₂

K₂
x= X
K₂

where K₁ = VT ratio
K₂= CT ratio (two CTs cross connected).

R and X are the line resistance and reactance values.

b) Asea and SWE Single CT Method

The current from the CT is fed via two interposing transformers one of which is
cross-connected.

c) Asea Two CT Method for use with Solid State LDC.

The two CT currents are summed in one interposing CT and subtracted in a second
interposing CT. this results in two vectors at 90° to each other.

EXAMPLE OF SINGLE CT METHOD

Most common on the Commission’s System. Refer to the instructions in the Commissioning
Programme for checking the correct polarity of R, X and Zero settings.

Diagram

340
 ZESA OVERHEAD LINES ELTC
ELTC 30

2). Sphere Gap lightning Arrestors

In this type of arrestor, the gap is provided by two similar spheres A and B. sphere B is
grounded while Sphere A is connected to the line B. this arrestor can protect the lines and
transformers against transient over voltage wave of any duration.

Diagram

341
3) Horn Gap Lightning Arrestor
Consists of two bent metal rods in the form of horns mounted on a vertical plane. The
horns are separated by a small air gap and they are connected in series with the line and
earth.

Diagram

ZESA OVERHEAD LINES ELTC

ELTC 31

5) Electrolyte Type
- Mostly employed on high voltage equipment.
- Principle of action: the action depends upon the fact that a thin film or aluminium
hydroxide, deposited on AI plates, immersed in an electrolyte, offer high resistance
at normal frequency (low voltage and low resistance at high voltage at transient
frequency).

6) Lead Oxide Arrestor

Principle: acts on the principle that there is a change in resistivity which occurs in certain
inorganic salts and heating e.g. lead peroxide PbO2 is a good conductor at ambient
temperature and almost an insulator at higher temperature.
Diagram

342
 ZESA OVERHEAD LINES ELTC
ELTC 32

4) Expulsion Type Lightning Arrestor

(Also known as protector tube)

It consists of two electrodes, one at each end and consists of fibre tube capable of
producing a gas when an arc is produced, the gas so evolved blows the arc out through the
bottom electrode.

Diagram

343
 ZESA OVERHEAD LINES ELTC
ELTC 33

7) Thyrite Lightning Arrestor

Thyrite has a remarkable property of being practically an insulating material at low voltage
while at higher voltages it behaves like an excellent conducting material when the voltae is
doubled, the resistance decreases in such a manner as to allow a current of 12.5 times

DIAGRAM

344
CROSS-SECTION OF THYRITE DISTRIBUTION ARRESTOR UNIT

ZESA OVERHEAD LINES ELTC

ELTC 34

8) Valve Type Lightning Arrestor

(Non-Linear diverter)

This consists of a divided spark gap in series with a non-linear resistor. The non-linear
resistor has the property that, as the current flows through it increases, its ohmic value
decreases rapidly (characteristics IR = Constant)

Diagram

345
 (a) (b)
VALVE TYPE ARRESTOR SIMPLIFIED LIN DIAGRAM FOR A
VALVE TYPE ARRESTOR

ZESA OVERHEAD LINES ELTC

ELTC 35

9) Atmospheric contamination of arrestor

This has plagued operators of power distribution and transmission ever since the first
overhead line was constructed.

In coastal area, contamination is in the form of salt-fog (worse form).

This can be any form of foreign deposits that reduces the insulation resistance.

Major causes
- Industrial fumes
- Diesel fumes
- Steam engines etc
- Dry weather (rains was away deposit)

Effect on lighting arrestor

346
 There are three specific ways in which external surface contamination can affect the
operation and life of a lightning arrestor:

1) External flashover (common)

2) Corona – if seals and gaskets are not properly shunted, leakage current flows.

3) Internal spark over – due to voltage surge between the gaps.

* Thus contamination should be taken into account when designing

arrestors

MCGRAW
EDISON
Power System
Group

RECLOSERS 280-40
Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase Electrical Apparatus

Reliable, electronically controlled overcurrent protection distribution systems is available for

installation on the pole, in substations, or in padmounted enclosures. The six reclosers in this
group provide service-proven dependability and long operating life. Commanded by McGraw-
Edison’s Type ME electronic control, these automatic circuit reclosers offer superior
coordination and application capability unmatched by other system protection apparatus.
Recloser operations are programmed on the electronic control panel with accurate, preset
tripping characteristics and reclosing times. Operating programs are precise and unvaried,
enabling closer coordination with other protective devices on the system. When system
requirements change, program settings are easily altered with no sacrifice of accuracy or
consistency.
The six distinct recloser types – RVE, RXE, VWE, VWVE, WE AND WVE – offer a load
selection of ratings to fit varied system needs. Recloser and control accessories enable further
tailoring of the protective program to achieve maximum system operating flexibility. Mounting
equipment available for pole or substation of the recloser wherever system requirements
demand.

Diagram
347
Figure 1.
Type RXE oil interrupting, three-phase, electronically controlled, automatic circuit recloser.

Figure 2
Type VWVE vacuum interrupting, three-phase, electronically controlled, automatic circuit
recloser
1

MCGRAW EDISON
Power Systems Group

280-40
Reclosers
Electrical Apparatus Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase

RATINGS AND CHARACTERISTICS FEATURES

Re-phase protection on systems rated through 14.4kV is provided by Types .. WE or VWE
reclosers, type VWVE be applied on systems rated through kV , Higher voltage system
protection ….. through 34.5 kV ) is provided by types RVE and WVE recloses. A rating
…… for this recloser group is shown in table 1. For ratings and basic application
information of other McGraw-Edison reclosers, see Apparatus Catalog 280-05.

OPERATION

1
October 1981 * Supersedes 12/78
348
Reclosing current transformers mounted in recloser supply fault-sensing information to the
electronic control. Tripping and rating signals from the control energize operating circuits
in the recloser. Due to single CT ratio for all ratings of the recloser. Stability in
coordination with other protective devices is provided by dual time current characteristics
from a choice of …..curved, minimum trip values, reclosing and resetting time settings and
a protection of accessories.

CLOSING SOLENOID
Contact-closing energy is provided by a closing solenoid which also stores energy …trip
mechanism. High-voltage closing solenoid are connected to the system … source side of
the recloser; selection of solenoid voltage rating is based on system phase-to-phase
operating voltage.

Low-voltage closing solenoids can be employed; auxiliary voltage must then be implied to
the recloser.

TABLE 1
Summary of Ratings
Type Nominal Voltage (kV) Maximum Continuous Maximum interrupting
Current (amps) Rating at Nominal Voltage
(sym amps)
RXE 14.4 400 6000
WE 14.4 560* 10000
VWE 14.4 560* 120000
VWVE 24.9 560* 120000
RVE 24.9 – 34.5 400 6000
WVE 24.9 – 34.5 560* 8000

*May be increased to 800 amps, continuous, with the addition of an 800-amp continuous current accessory
Oil or Vacuum Interruption
A choice of interrupting medium is available. Types RVE, RXE, WE and VWE reclosers
use oil as the arc interrupting medium. Movable bridge-type contact provides two breaks in
series on each phase. Separate self-generating interrupter chambers at each of the two
breaks provide for effective interruption of all currents, from minimum load to rated
maximum fault.
Vacuum interruption used in Types VWE, VWVE, offers considerably longer duty cycles
and long contact life. A single separating contacts inside the vacuum interrupter. An arcing
is contained within the vacuum interrupter. All arcing is contained within the vacuum
envelope. Low-energy arc interruption in a vacuum results in far less shock and
demonstration, extending the recloser mechanism life.

Upgraded Protection
Existing recloser installations can be up-graded easily to vacuum interruption. Type VWE
and VWVE reclosers – with the same horizontal dimensions as other reclosers in this group
– can be installed in existing mountings without disturbing the pole or substation frame.
Just a change out of the recloser brings longer interrupter life and increased interrupting
capability.
Type VWE and VWVE oil-insulated re-closers are smaller than comparably rated air-
insulated vacuum apparatus. As a result, where air-insulated vacuum equipment may be too
bulky for pole mounting, these reclosers present a low-profile installation.
349
 ORDERING INFORMATION

A complete electronically controlled recloser installation includes these items.

 Recloser and accessories;
 Electronic control and accessories;
 Interconnecting control cable;
 Recloser mounting equipment ( if required).

Detailed information on the control and accessories is in Apparatus Catalog Section 280-75.
See 280-80 for recloser accessories and 280-85 for mounting equipment.

Basic recloser price also includes basic electronic control and a 7-ft interconnecting cable.
Accessories and mounting equipment are in Part 40 of Catalog Section 280-01. Prices of the
electronic control accessories are in Part 75 of 280-01.

MCGRAW
EDISON
Power System
Group

Reclosers 280-
40
Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase Electrical Apparatus

Order must include catalog number and …….. of each of the following:
Basic recloser (refer to Tables 2 and 3); recloser accessories (if required; see tables 4-11);
Basic electronic control; plug-in components and operating sequence (see tables 12 and 13);
Control cable length (see Table 14);

350
 Control accessories ( if required see tables 15-19);
Recloser mounting equipment, factory resembles; and kits (if required; see table 20-23)

TABLE 2 TABLE 5
Recloser Catalog Numbers Multi-Ratio Bushing -Current
Recloser Type Catalog Number Transformers for Field Installation
600:5 for Meeting
RXE KRXE* Description Catalogue
WE KWE*
Number
VWE KVWE*
VWVE KVWVE* Slip-on bushing current
RVE KRVE* Transformer kit; one
WVE KWVE* BCT per kit ……… KA712L2
Wiring kit for slip-on Place
asterisk in catalog number with closing BCT………………. KA895R coil
number form Table 3 below.
TABLE 3
Closing Coil Voltage Code Numbers
Phase-to-phase Closing Coil Code No
Operating Voltage ± 15%
kV
2.4 11
3.3 10
4.16-4.8 2
6.0 6
7.2- 8.32 3
11.0 9
12.0-13.2 4
14.4 5
17.0 12
20.0 11
23.0-24.9 13
34.5 14
Voltage Closing Coils * (Vdc)
125 7
250 8
Requires either low-voltage dc closing accessory (KA631R) or low-voltage ac closing accessory
(KA742R). Order separately.

MCGRAW EDISON
Power Systems Group

280-40
Reclosers
Electrical Apparatus Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase

Table 4
Multi-Ratio Bushing-Current Transformers Factory – Installed on Load –Side Bushings 2,4 and
6*
351
 Description Catalog Number**
Type RVE
Three 600:5 BCTs on standard-creepage bushings ………………………… KA19RB3X
Three 600:5 BCTs on 26 ½-in.-creepage bushings ………………………… KA21RV3X***
Type RXE
Three 600:5 BCTs on standard-creepage bushings ………………………… KA844R3X
Three 600:5 BCTs on 17-in.-creepage bushings …………………………… KA637R3X***
Types VWE and WE
Three 600:5 BCTs on standard-creepage bushings ………………………… KA804W3X
Three 600:5 BTCs on 17-in.-creepage bushings …………………………… KA110W3X***
Three 1200:5 BCTs on standard-creepage bushings ………………………. KA827W3X
Types VWVE and WVE
Three 600:5 BCTs on standard-creepage bushings ………………………… KA12WV3X
Three 600:5 BCTs on 26 ½-in.-creepage bushings ………………………… KA14WV3X***
Three 1200:5 BCTs on standard-creepage bushings ………………………. KA24WV3X

*To specify accessory BCTs on source-side bushings, include the digit 9 after the A in the catalog number
and specify source-side bushings in the order description.
**If factory wiring is ordered, replace the X in the catalog number with the ratio to be connected:
1200=1200:5. 1000 = 1000:5; 900= 900:5; 800 = 800:5; 600 = 600:5; 500 = 500:5; 450 = 450:5; 400 =
400:5; 300 = 300:5; 250 = 250:5; 200 = 200:5; 150 = 150:5; 100 = 100:5; 50 = 50:5.
***Catalog number includes extra-creepage-distance bushings

TABLE 6
Remote Operation and Indication; Factory – Installed
Description Catalog Number
Three-stage auxiliary switch with six
independent contacts* ……………………………………………. KA369R3
Low-voltage dc closing; requires that recloser
be ordered with dc closing coil
125 vdc
Types RVE, RXE, WE, WVE ………………………………….. KA631R3
Types VWE, VWVE …………………………………………… KA631R7
250 vdc
Types RVE, RXE, WE, WVE …………………………………… KA631R4
Types VWE, VWVE …………………………………………… KA631R8
Low-voltage ac closing; requires that recloser
be ordered with dc closing coil
120 vac
Types RVE, RXE, WE, WVE ………………………………………….. KA742R3
Types VWE, VWVE …………………………………………………… KA742R7
240 VAC
Types RVE, RXE, WE, WVE …………………………………………. KA742R4
Types VWE, VWVE ………………………………………………….. KA742R8
Closing-coil transfer switch
Type RVE …………………………………………………………………… KA1169R5**
Type RXE ………………………………………………………………….. KA1169R6
Type WE ………………………………………………………………… KA1169R7
Type WVE …………………………………………………………………... KA1169R8**
Type VWE …………………………………………………………………... KA1169R11
Type VWVE ………………………………………………………………… KA1169R12

*Auxiliary switches are supplied with an equal number of a and b contacts unless otherwise specified.
** Transfer switch can be used on 2.4 -24.9-kV distribution systems. Switch has 27-kV max design and 125-kV
Bil ratings and can be used with higher-rated recloser where these ratings are adequate.

TABLE 7
Bushings and Terminals; Factory- Installed
Description Catalog Number
352
 17-in.-creepage bushings
Type RXE …………………………………………………… KA562R1
Type WE and VWE …………………………………………. KA25W
26 ½-in. creepage and bushings
Types WVE and VWVE ……………………………………… KA13WV
Types RVE ……………………………………………………. KA20RV
Flat-pad terminals; two-hole
Types RXE and RVE ………………………………………….. KA579R1
Types WE, WVE, VWE and VWVE …………………………. KA82W
Flat-pad terminals; four-hole
Type RXE ……………………………………………………… KA1146R
Types WE and VWE …………………………………………… KA156W
Stud terminals
Types RVE and RXE …………………………………………… KA842R1
Types VWE, VWVE, WE and WVE …………………………… KA800W1

TABLE 8
Continuous –Current Accessory; Factory installed
Description Catalog Number
100-amp continuous-current accessory
With eyebolt terminals
Types WE and WVE …………………………………………… KA59WE3
Types VWE and VWVE …………………………………………. KRW55VB
With stud-type terminals
Types WE and WVE …………………………………………….. KA59WE1
Types WVE and VWVE ………………………………………… KRW55VA

TABLE 9
Battery Charger; Factory - Installed
Description Catalog Number
CT-type battery charger power source * KA16ERE
……………………………….
Requires electronic control modification KA1144ME; see Table 18, page 7

TABLE 10
Metering*
Description Catalog Number
Set of three outdoor, socket mounted, thermal-demand meters;
Five-amp movement /five-amp scale
With instantaneous indicating elements …………………………. KRW32V1-3
Without instantaneous indicating elements ……………………… KRW324V20-3
Vertical, rain-tight meter trough; three sockets
With circuit closing contacts ** ………………………………… KA335R3
A metering accessory is also available installed in the upper portion of a double-size Type ME electronic control
cabinet; see 280-01; part 75
KA584R4 bracket required if meters are to be mounted on KA584R1 substation frame.

MCGRAW
EDISON
Power System
Group

Reclosers 280-40
Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase Electrical Apparatus

353
TABLE 11
Service-Related; hardware
Description Catalog Number
Manual closing tool; deenergized recloser; factory installed ………… KA476R
C-handle closing tool; deenergized recloser …………………………. KA90R
Oil-level sight gage; factory-installed ……………………………….. KA161W
Stainless steel hardware; factory-installed
Standard recloser ……………………………………………………. KA635R1
Recloser with three BCTs ……………………………………………… KA635R5

TABLE 12
Basic Type ME Electronic Recloser Control
Description Catalog Number
Type ME electronic control with ground and phase trip and one set of
programming plug-in components ……………………………….. KMEB

TABLE 13:
Type ME Control Programming Plug-In Components and Dial Settings
One set of programming plug-in components is included in the price of the Type ME electronic control. Specify
each item listed in Table 13 to assure proper control operating program.
Description Catalog Number
Reclosing intervals
Select reclosing interval of 1, 2, 5, 7, 10, 15, 30, 45, 60 seconds or
INST (instantaneous). (60 sec and INST are single-value plugs)
First reclosing plug—seconds ………………………………… KA1016ME — -1
Second reclosing plug— seconds …………………………….. KA1016ME — -2
Third reclosing plug—seconds ………………………………. KA1016ME — -3
Ground-trip timing characteristics
Select ground-trip curve 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 23, 14, 15, 16, 17, 18,
or K (see R280-91-26 for time-current curves):
Ground-trip timing plug— in socket 1
for— operations ………………………………………………. KA216ME — -1 —
Ground-trip timing plug — in socket 2
For — operations ……………………………………………… KA216ME — -2 —
Phase-trip timing characteristics
Select phase-trip curve A,B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R,
T, V, W, Y, or Z (see R280-91-26 for time-current curves):
Phase-trip timing plus—in socket 1
For — operations ………………………………………………. KA217ME — -1 —
Phase-trip timing plus — in socket 2
For — operations …………………………………………………. KA217ME — -2 —
Reset delay time
Select reset delay time of 10, 15, 20, 30, 45, 90, 120, or 180 seconds. (20sec
is single-value plug):
Reset plug — seconds (timed from successful reclosure) ………. KA1015ME —
Minimum-trip current
Ground minimum-trip resistor — amps (single unit):
Select 25, 35, 50, 70, 100, 120, 140, 170, 200, 240, 280, 340, 400, 480, or
560 amps. ………………………………………………………….. KA244ME —
Phase minimum-trip resistors — amps (single unit):
Select 100, 120, 140, 170, 200, 240, 280, 300, 340, 400, 480, 560, 600,
680, 800, 960, * or 1120**amps ………………………………. KA243ME —
*The interrupting rating of the recloser-control combination is limited to 30 times minimum trip or 120 times the
ground minimum trip selected (whichever is less), but not to exceed the maximum interrupting rating of the
recloser. Phase- and ground-trip protective accessories in the control can extend the interrupting limit to the
maximum interrupting rating of the recloser.
**not normally recommended for use with RVE or RXE reclosers

354
TABLE 14
Control Cable
Description Catalog Number
Standard 7-ft cable ………………………………………………… KA1ME7
Longer cable (125 ft maximum)
8 to 80 ft …………………………………………………………… KA1MEXX*
81 to 125ft ………………………………………………………….. KA18MEXX*
*substitute length in feet for xx
TABLE 15
Type ME Characteristic-Modifying Accessories; Factory – Installed*
Description Catalog Number
Instantaneous trip
Specify minimum-trip multiple and control operation on which accessory is to operate.
Phase only: Multiple pf 1.4, 2.0, 2.8, 4.0 or 5.6 ……………………………… KA1037ME1
Phase only: Multiple of 5.6, 8.0, 11.2, 16.0 or 22.4 ………………………….. KA1037ME2
Phase and ground: Both with multiplies of 1.4, 2.0, 2.8, 4.0 or 5.6 …………. KA1037ME5
Phase and ground: Both with multiples of 5.6, 8.0, 11.2, 16.0 or 22.4……….. KA1037ME8
Phase and ground: Phase multiple of 1.4, 2.0, 2.8, 4.0, or 5.6; ground multiple
of 5.6, 8.0, 11.2, 16.0, or 22.4 ……………………………………………. KA1037ME6
Phase and ground: Phase multiple of 5.6, 8.0, 11.2, 16.0, or 22.4; ground multiple of
1.4, 2.0, 2.8, 4.0 or 5.6 ……………………………………………… KA1037ME7
Instantaneous lockout
Specify minimum-trip multiple and control operation on which accessory is to operate
Phase only: Multiple pf 1.4, 2.0, 2.8, 4.0 or 5.6 ……………………………… KA1036ME1
Phase only: Multiple of 5.6, 8.0, 11.2, 16.0 or 22.4 ………………………….. KA1036ME2
Phase and ground: Both with multiplies of 1.4, 2.0, 2.8, 4.0 or 5.6 …………. KA1036ME5
Phase and ground: Both with multiples of 5.6, 8.0, 11.2, 16.0 or 22.4……….. KA1036ME8
Phase and ground: Phase multiple of 1.4, 2.0, 2.8, 4.0, or 5.6; ground multiple
of 5.6, 8.0, 11.2, 16.0, or 22.4 ……………………………………………. KA1036ME6
Phase and ground: Phase multiple of 5.6, 8.0, 11.2, 16.0, or 22.4; ground multiple of
1.4, 2.0, 2.8, 4.0 or 5.6 ……………………………………………… KA1036ME7
Low-current ground trip (specify 5.8- or 10.0 amp trip) **
Substation frame mounting ……………………………………………………….. KA1009ME1
Pole mounting ………………………………………………………………………. KA1009ME2
Minimum-trip doubler
Remotely operated; phase trip or phase and grounf trip. Specify whether minimum trip
is to be doubled for an open or closed external contact KA1002ME
……………………………………
Locally operated KA1000ME1
Phase trip only ………………………………………………………………………. KA1000ME2
Phase and ground trip ………………………………………………………………
Reclose block; 120-vac KA333ME11
While deenergized …………………………………………………………………. KA333ME12
While deenergized …………………………………………………………………. KA418ME5
Sequence coordination ……………………………………………………………….
Protective accessory KA1021ME2
Phase trip only ………………………………………………………………………. KA1021ME1
Ground trip only ……………………………………………………………………… KA1021ME3
Phase and ground trip ……………………………………………………………….
*for complete description of accessories, see Section 280-75
*The cables of the low-current ground trip accessory are used in place of the standard control-to-recloser cable,
therefore, do not order a separate control cable when the low-current ground –trip accessory is supplied.

MCGRAW EDISON
Power Systems Group

280-40 Reclosers
Electrical Apparatus Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase
355
TABLE 16
Remote Control and Indication; Factory Installed

Description Catalog Number

Remote close …………………………………………………………………….. KA316ME4
Remote trip ………………………………………………………………….. KA1004ME
Remote lockout …………………………………………………………………… KA639ME3
Control-lockout indicator (contacts) ………………………………………………. KA472ME3
Fault indicator
Annunciator-type target; automatically reset;
Phase only …………………………………………………………………….. KA1137ME1
Annunciator-type target, automatically reset;
Phase and ground …………………………………………………………….. KA1137ME2
Counter-type; phase only ………………………………………………………… KA1030ME1
Counter-type; phase and ground …………………………………………………. KA1030ME2
Combination (both annunciator and counter types; phase only requires double-size
cabinet) * …………………………………………………………………………… KA1130ME2
Battery-charging current indicator
In upper portion of double-size cabinet* ………………………………………… KA608ME3
In separate enclosure …………………………………………………………….. KA282ME2
Load-current indicator in upper portion of double-size cabinet* …………………. KA545ME3

TABLE 17
Metering Factory-Installed
Description Catalog Number
Three thermal amp-demand metres; five-amp movement/five-amp
Scale; in upper portion of double-size cabinet; require cable
Accessory KA1153ME from BCTs to control cabinet*
Without Instantaneous indicating elements ………………………………….. KA811TR5M5
With instantaneous indicating elements …………………………………….. KA812TR5M5
Cable accessory for thermal amp-demand meters** …………………………….. KA885R—***
*Double-size cabinet (Table 19) and cable accessoryKA88R or KA1153ME must be ordered
separately.
**Cable accessory is not required when factory-assembly KA804WE1 is ordered.
***Add cable length in feet, measuring points are defined in Section 280-75.

Table 18
Service-Related; Factory-Installed

Description Catalog Number

Thermostatically controlled heater; on 85F and below/off
100F and above; 120-vac single or double size cabinet …………………….. KA542ME10
Capacitor backup trip
Control in single-size cabinet ……………………………………………. KA1119ME1
Control in double-size cabinet …………………………………………… KA1119ME2
Temperature-regulated battery charger; 120-vac ……………………………. KA1174ME1
Manual trip tester …………………………………………………………….. KA1007ME
Control –fuse eliminator ……………………………………………………….. KA531ME3
Control-cable locking sleeve …………………………………………………. KA614ME1
Fused convenience receptacle; 120-vac ………………………………………… KA671ME
Spare trip-resistor holder ……………………………………………………….. KA814ME
Factory modification when Type ME control is to be used with
CT-type battery charger power source** ………………………………………. KA1144ME

356
 *Double-size cabinet must be ordered separately; see table 19
**CT-type battery charger power source must be ordered as a recloser accessory.

Table 19
Double-Size Cabinet: Factory-Installed
Description Catalog number
Double-size cabinet for Type ME electronic accessories* …………………… KA695ME

Table 20
Recloser Mounting Equipment
The following mounting equipment is available for either pole or substation installation of these
reclosers. Mounting equipment dimensions are shown in Section 280-5
Description Catalog Number
Substation mounting equipment
Basic mounting frame ………………………………………………………. KA584R1
Mounting brackets
Single-size ME control and meter trough on
KA584R1 frame ……………………………………………………...... KA584R4
Double-size ME control and meter trough on
KA584R1 frame ………………………………………………............... KA584R5
Single or double-size ME control on load side of
KA584R1 frame ……………………………………………………….. KA584R9
Removable tank-lifting windlass for KA584R1 frame …………………….. KA584R2
Pole-mounting equipment
Single-pole mounting hanger ………………………………………………. KA146W3
Tank-lifting windlass for single-pole hanger ……………………………… KA146W2
Surge arrestor mounting bracket……………………………………………. KA126H3

Factory Assemblies and Kits

Reclosers can be factory-assembled in
Lifting frames and external meters can
Be factory-wired. Also, wiring kits are
Cable for field installation of inter-accessory wiring

Table 21
Factory Assembly of Recloser and Accessories in KA584R1 Substation Mounting Frame*
Description Catalog Number
Recloser and Type ME electronic control on frame
no accessories ………………………………………………………………. KA800WE
Recloser and Type ME electronic control with load-side BCT wired
to meter trough ………………………………………………………. KA801WE
Recloser and Type ME electronic control with source-side BTCs
wired to meter trough ……………………………………………………. KA802WE1
Recloser and ME control with source-or load-side BCTs wired
To KA811TR or KA812TR meters in double-size cabinet ………………. KA804WE1
Catalog number covers factory assembling only; recloser, accessories, and mounting must be specified
separately.
TABLE 22
Factory Assembly of Recloser in KA146WE Single-Pole Mounting Frame*

Description Catalog Number

Recloser only; with or without BCTs ……………………………………………… KA881R2
Catalog number covers factory assembling only; recloser and mounting must be specified separately.

357
Table 23
Conduit and Wiring Kits for Field Installation*
Description Catalog Number
Recloser in KA584R1 substation frame
Kit for wiring load-side BCTs to meter trough ………………………………… KA801WE2
Kit for wiring source-side BCTs to meter trough ……………………………… KA802WE2
Recloser in KA146W3 single-pole mounting frame
Conduit kit for BCTs when recloser is to be mounted with BCTs
On pole side ……………………………………………………………………… KA883R
Cable for wiring BCTs to meter trough ………………………………………………. KA885R***

Kit includes all conduit and wire necessary to connect recloser and accessories specified. Kits are
shipped and assembled.
Catalog number includes 7-ft cable. If longer cables is required, specify length on order

Features and Detailed Description

McGraw-Edison Types RVE, RXE, RXE, VWE,VWVE; WE, and WVE electronically controlled
three-phase oil reclosers protect systems operating through 35.4 kV (see ratings and specifications, page

358
15). These ratings and the wide range of electronic control flexibility permit a variety of application
requirements to be met.

Basically the same in operation as hydraulically controlled reclosers (Catalog operation 28-30), these
reclosers possess the added operating flexibility of electric control.
The choice of oil or vacuum as the arc interrupting medium is available:
 Types RVE, RXE, WE, and WVE reclosers use oil (Figure 3). Bridge-type contacts provide
two current breaks in series for each phase. Each current break employs a separate vented, self-
generating, arc-interrupting chamber for effective interruption of the recloser’s full current
range.

 Vacuum interruption is utilized by Types VWE and VWVE reclosers (Figure 4). A single break
on each phase is accomplished by separating a set of contacts within the vacuum chamber.
Low-energy arc interruption in a vacuum extends the duty cycle and results in less shock
demonstration, extending recloser mechanism life.

 Closing force is supplied by a closing solenoid closes the main contacts of all phases while
simultaneously charging the opening springs in preparation for a tripping operation. A battery
in the control cabinet signals tripping and closing.

Diagram

Figure 3
Untanked view of Type recloser illustrates simplified mechanism resulting from electronic control.
Construction of Types RVE, VWE, VWVE and WVE is similar, except for vacuum interrupters on VWE
and VWVE (Figure 4).

MCGRAW EDISON
Power Systems Group
359
 280-40
Reclosers
Electrical Apparatus Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase

Fault currents are sensed by three sensitive current transformers. 1000:1 ratio rated in the recloser.
These CTs provide continuous measurement of line current, monitored by the electronic control. When
minimum-trip-current value is exceeded …, after a time delay, the control energizes the trip solenoid in
the recloser. This increases the tripping springs, opening the ..in contacts of all three phases. If reclosing
is programmed, the control activates the closing mechanism. The reclosers are self-contained, they
require no external power source (except as required by certain accessories).
The Type ME control provides simple selector-switch determination of phase and ground-trip
sequences and operations to lockout. minimum phase- and ground-trip values, timing of tripping and
reclosing and resetting timing are established by plug-in components. Application flexibility is
enhanced by dual-timing characteristics from a choice of time current curves for phase and ground
tripping levels.
Utilizing available accessories, the control’s range of minimum-trip values can be extended to include
from 50 to 1120 amps for phase values and from 5.8 to 560 amps for ground, depending on recloser
type. Other accessories provide remote control or special programming sequences.

Diagram

Fig 4
Untanked Type VWE vacuum recloser (shown from closing contactor side).

360
 MCGRAW
EDISON
Power System
Group

RECLOSERS 280-40
Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase Electrical Apparatus

CONSTRUCTION
Recloser

Like other McGraw-Edison reclosers, these are designed for long service life and minimum
maintenance. Heads are aluminium castings. Tanks are heavy-gage steel, vanished with an inhibiting
epoxy prime…followed by a finish cot of thermos-rating acrylic paint (Munsell 5BG 7.0/0.4; light gray
is standard).
An O-ring gasket confined in a groove provides an oil tight and weatherproof seal between head and
tank. A ½ -in. brass sampling-and-drain valve near the bottom of the tank is standard.
The recloser is supported by bolts although the head casting to the mounting. …complete internal
mechanism is suspended from the head casting, allowing mechanism and head assembly. Lowering the
tank with a wire rope winch available as an accessory) permits easy access to contacts.
Insulating supports from which the three interrupters are suspended are filament-wound glass epoxy for
high electronic and mechanical strength and moisture resistance.

Interrupter (Figure 5)
Fast arc interruption (down to 2 ½ cycles clearing is furnished by bridge-type contacts, providing two
current breaks in series per phase. The bayonet-type silver plated tungsten alloy moving contacts resist
erosion and provide good conductance. The stationary-contact assemblies are tulip-type clusters of
silver-plated contact fingers held by garter springs. The contacts are self-cleaning sue to the wiping
action of opening and closing.

Each current break has a self-generating-type arc interrupter structure including a series vented
chambers. As the contacts open, the arc generates gas pressure in the upper chamber, which blasts oil
across the arch and out through the vents. As a result, arc extinction is fast, and arc-energy levels are
not increase as quickly at higher fault-current levels.

Vacuum Interrupter (Figure 6)

Type VWE and RWVE reclosers vacuum interrupters – used in other McGraw-Edison fault protection
apparatus since they have established a superb field performance record. Produced at McGraw-Edison’s
Kyle Products Plant, the interrupters high reliability results from excellent development and vacuum
technology programs that offer the broadest line of vacuum reclosers.

Major interrupter insulation is provided by two high-alumina ceramic cylinders. Ceramic is used, rather
than glass, because it’s far stronger and withstands the higher vacuum bake out temperature required for
interrupter cleanliness and long life. End cups and outer envelope, made of a vacuum melted alloy are
joined to the ceramic by a butt seal brazing method of proved strength and reliability. A monel bellows

361
completes the vacuum enclosure, permitting the moving contact to travel its one-half inch stroke while
maintaining envelope integrity.

The copper-alloy contact material chosen for its anti-welding and high current interrupting capabilities,
is processed in specialized vacuum equipment.
Extensive processing and assembly precautions, including clean room facilities, insure interrupters that
are free of contamination from atmosphere or handling and are highly reliable.

Diagram

Fig 5
General construction of self-generating interrupter used on Types RVE, RXE, WE and WVE reclosers.

Figure 6
Cross-section of Type VW recloser vacuum interrupter

362
MCGRAW EDISON
Power Systems Group

280-40
Reclosers
Electrical Apparatus Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase

RECLOSER OPERATION
Tripping

When current flow exceeds the minimum trip value needed to satisfy the progrmmed timing
characteristics, the control battery energizes a trip solenoid in the recloser. This solenoid
releases a latch, and a spring-loaded toggle assembly opens the recloser contacts. Maximum
clearing time is 2.5 cycles for Types RVE and RXE reclosers; 2.7 cycles for Types VWE,
VWVE, WE and WVE reclosers.

Closing
Closing force – as well as the force to charge the opening springs – is supplied by a high –
voltage closing solenoid connected phase-to-phase (Figure 7). When the recloser contacts are
closed, the solenoid plunger is latched in the down position. This latch is tripped
simultaneously with the release of the recloser opening springs and the solenoid plunger moves
upward for a closing operation.

At the programmed reclosing time, the electronic control energizes a rotary solenoid in the
recloser. Movement of the rotary solenoid allows a high-voltage contactor to close
momentarily, connecting the closing solenoid to the line. The plunger is pulled into the
solenoid closing the recloser contacts and charging the opening springs. Plunger movement
also opens the high-voltage contactor (Figure 8), de-energizing the closing solenoid. Closing
operation of the recloser mechanisms activates a switch (b contact) in the recloser,
disconnecting the rotary solenoid from the electronic control.

The closing solenoid is designed for repeated-momentary rather than continuous operation. If
malfunction of the solenoid plunger or the closing-coil contactor results in the closing solenoid
energizing for an extended period, a closing-solenoid fuse within the recloser opens the high
voltage circuit, protecting the closing solenoid from thermal damage.

Voltage loss on the source side of an open recloser could result in a continuous closing signal
from the electronic reclosing control. Therefore, further protection of the closing solenoid, the
rotary solenoid and the electronic control battery is provided by a control fuse mounted in the
electronic control panel. The control use opens the circuit before the control battery can be
363
drained or the rotary solenoid damaged from continuous operation. During a low-voltage
condition on the source side of an open recloser- which could result in incomplete travel of the
closing solenoid plunger – the control fuse will again open before damage occurs.

Diagram

Figure 7
Diagram showing phase-to-phase connection of high voltage closing solenoid.

Manual Operation

The recloser can be manually tripped at any time by lowering the yellow manual operating handle under
the sleet hood. With the handle down , the control cannot close the recloser. Raising the handle permits
closure, provided the connected and energized control is not in the lockout position. Similarly, the
recloser can be operated from the manual control switch on the electronic control panel, provided the
manual operating handle is up. A red flag adjacent to the manual operating handle provides contact
position indication.

Diagram

364
Figure 8
High-voltage closing solenoid contactor

MCGRAW
EDISON
Power System
Group

RECLOSERS 280-40
Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase Electrical Apparatus

TYPE ME ELECTRONIC For installations where a 120-vac The operating panel of the
CONTROL auxiliary power source is not electronic control is shown in
The McGraw-Edison Type ME available at the control, the recloser Figure 9. Control programming
electronic control utilizes solid- must be equipped with a bushing components are in the upper (dark)
state circuitry to provide the CT accessory to supply the trickle portion of the panel, while contract
intelligence for performing all the charger directly from the primary switches and test indicates for
command functions involved in line. However, to maintain a full manual operation are grouped in
automatic recloser operation. The charge on the battery, the line the lower (Light) portion of the
only mechanical devices are current must exceed 40amps for at panel.
sequence relay and operations least 12hours per day.
counter. NOTE: if ordering a new recloser to Operating sequence and the
operate with an existing control, make number of operations to lockout
Current Sensing sure the control is equipped with a and established by the three
potential battery charge or order the
The recloser is provided with three positive-stop …selectors on the
CT charger accessory for the recloser-
1000:1 sensing current control combination has an operational upper left of the panel. From one to
transformers. These provide both battery charger. four operations to lockout and
phase and ground (zero sequence) A set of terminals on the control selected on the center knob. At left
currents. They are connected to the panel can be used for testing is the ground-trip selector which
Type ME control cabinet by means battery voltage and net current flow establishes the number of fast
of a plug-in cable, which can be up (charge current les quiescent ground-trip operation (from 0 to4)
to 125ft length, thus permitting battery drain) into the battery if according to the time-current
mounting of the control remote charger is connected. If the battery characteristics plus in ground-trip
from the recloser. charger is disconnected, current Sockets. 1. the balance of ground
test terminal can be used for testing trip operation to lockout then will
Battery and Charging Supply quiescent battery-drain current. be according to the delayed
Recloser tripping and closing are Panel Component Functions characteristic plug in ground trip
imitated for signals from the Automatic control functions of the Socket. 2. The phase-trip sequence
control unit which is lowered by a Type ME control are established by selector at right is similar in
24-volt nickel-cadmium battery in a static low-voltage, low-energy operation to the ground-trip
the control cabinet. Battery charge system which include a number of selector.
maintained by a trickle charger plug-in components at switch
supplied from an external 120-vac settings.
auxiliary supply.

365
Figure 9: Electronic Control Panel

MCGRAW EDISON
Power Systems Group

280-40 Reclosers
Electrical Apparatus Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase

Reclosing interval times for successive reclosing operations are published by the solid-state, plug-in
components at the upper right of the panel. Instantaneous reclosing plug (INST). Multiple-setting
reclosing plug with 1-trough 45 second intervals, and a 60 second single-value plug ware available.
Instantaneous reclosing interval for all reclosers in this group is approximately 40 cycles.
(Instantaneous should be used only for the first reclosing interval).

Minimum-trip values are set by plug-in resistors (center of panel) on each case, plus ground trip.
Minimum-trip panel is independent of, but cannot exceed …. The recloser’s continuous-current rating.

Time-current characteristics for case and ground tripping are governed by the plug-in resistance-
capacitance work components at the right of the control panel. In addition to quick field replacement,
the timing plugs provide the precise control of a stable, nonadjustable …that cannot be incorrectly
adjusted. Specified time-current curves are accurate within ± 10%. See R280-91-26 for recloser
appearing time-current curves for the various phase- and ground-trip plugs available.

On both phase and ground trip, fast operations are according to the plug-in socket 1 and delayed
operations to plug-in socket 2. When dual timing is employed, the faster characteristics of Socket 1
always preceded the slower curve the plug in Socket 2.

Reset time (10 to 180 seconds) is controlled by multiple-setting plug-in component in the lower right
portion of the panel. As displayed on the yellow plug device, eight reset-delay time are available. 20-
second single value plug is also available. As with the reclosing plugs, reset time can be changed easily
but once the receptacle the setting locked in unless the plug id withdrawn.

The standard operation mode measures the reset-delay time from a successful reclosure. The control
can be programmed to measure the reset delay for the first trip operation in an operating sequence by
connection on the tie-board of the electronic control. After the reset time expires and the control has not
locked out, it automatically resets to the beginning of its program.

Manual Control Functions

366
Manual controls are grouped together at the bottom of the control panel.

Manual closing and tripping is performed with the manual control switch. Moving the switch to TRIP
opens the recloser and locks out the control. Moving the switch to CLOSE resets the control and closes
the recloser.

When held the CLOSE position, the switch provides the control with cold-load-pickup capability by
altering the trip timing characteristic. The socket 1 timing plugs are bypassed and all overcurrent trip
operations to lockout occur on the slower-time current characteristics curves of the Socket 2 timing
plugs for both phase and ground.

Ground-trip blocking, activated by a toggle switch, disables the ground-trip functions of the control.
Non-reclosing after an automatic trip, needed to meet certain safety requirements, is accomplished with
another toggle switch.

Lockout indication incorporates an indicator lamp and a double-throw switch. When the switch is
down the lamp lights if the control is locked out the up position tests the lamp.

Control Operation (Figure 10)

Bushing CTs in the recloser provide the control with the basic line current level information. The CT
outputs – each proportional to the line current of that phase – are rectified and mixed in the sensing
network to produce a signal proportional to the highest phase current flowing through the recloser.
When the current level exceeds the selected minimum-trip value, the trip-timing circuit is activated.

The current magnitude – integrated with time in accordance with the time-current produces a signal
which fires the trip silicon-controlled rectifier (SCR). The SCR in turn connects the 24-volt control
battery to the recloser trip solenoid. Actuation of the tri solenoid releases the charged trip springs,
operating the mechanism and opening the recloser contacts. The trip SCR also steps the control
sequence relay and actuates the operations counter. Ground-fault tripping is accomplished in a similar
manner.

Recloser tripping energizes the reclose-timing circuit. When the preset reclosing time elapsed, a close-
initiating signal energizes the rotary-closing solenoid in the recloser, in turn actuating the closing coil
contractor to close the recloser and charge the tripping springs.

Upon reclosure, if the phase and ground currents are below their minimum-trip level (successful
reclosure), reset timing is activated. The sequence relay is reset to its home (start) position at the
preselected time established by the reset-delay plug, and the control is ready for another sequence of
operations. Should the fault restart before the reset delay times out, the timing is forgotten and the
control will continue its programmed tripping-reclosing sequence where it let off.

Upon reclosure, if the phase and or ground currents are above their minimum-trip levels (fault still
present), additional timing, tripping and reclose functions will occur with operating characteristics
established by the plug-in components which are appropriately switched into the circuit by the sequence
relay. When the predetermined trips to lockout occur, the sequence relay stops in the lockout position
with the recloser open. The manual control switch must be operated to CLOSE to reset the sequence
relay and close the recloser.

Diagram

367
Figure 10.
Functional block diagram of Type ME electronic control
MCGRAW
EDISON
Power System
Group

Reclosers 280-40
Types RVE, RXE, VWE, VWVE, WE, WVE; Three-Phase Electrical Apparatus

RATINGS AND SPECIFICATIONS

TABLE 24
Electrical Ratings
Description Type RXE Types Type Type RVE Type
WE,VWE VWVE WVE
Nominal system voltage (kV) 2.4-14.4 2.4-14.4 24.9 24.9-34.5 24.9-34.5
Maximum rated voltage (kV) 15.5 15.5 27 38 38
Rated impulse withstand voltage
(BIL) (kV crest)………………. 110 110 125 150 150
60-Hertz withstand voltage (kV rms)
Dry, one min …………………. 50 50 60 70 70
Wet, ten sec …………………… 45 45 50 60 60
Rated maximum continuous current
(amps) ………………………… 400 560* 560* 400 560*
Bushing Creepage distance (in.) ….. 5 5 18 17 18
11 11
8 8

* Extendable to 800 amps with accessory. BIL for type WVE then becomes 125kV.

TABLE 25
Interrupting Ratings – Phase Trip
Interrupting Ratings
Minimum (rms symmetrical amps)
Trip Type RXE Type WE Type VWE Type Type RVE 400 Type WVE
Ratings 400 Amps 560 Amps Max * 560 Amps VWVE 560 Amps Max 560 Amps
(amps) Max @ Max * Amps Max Max*
14.4 kV @ 4.8kV @ 14.4 @14.4kV @24.9kV @24.9-34.5kV @24.9-34.5kV
kV

368
 100 3000** 3000** 3000** 3000** 3000** 3000** 3000**
120 3600** 3600** 3600** 3600** 3600** 3600** 3600**
140 4200** 4200** 4200** 4200** 4200** 4200** 4200**
170 5100** 5100** 5100** 5100** 5100** 5100** 5100**

200 6000 6000** 6000** 6000*8 6000** 6000 6000**

240 6000 7200** 7200** 7200** 7200** 6000 7200**
280 6000 8400** 8400** 8400** 8400** 6000 8000
300 6000 9000** 9000** 9000** 9000** 6000 8000

340 6000 10200** 10000 10200** 10200** 6000 8000

400 6000 12000 10000 12000 12000 6000 8000
480 6000 12000 10000 12000 12000 6000 8000
560 6000 12000 10000 12000 12000 6000 8000

600 6000 12000 10000 12000 12000 6000 8000

680 6000 12000 10000 12000 12000 6000 8000
800 6000 12000 10000 12000 12000 6000 8000
960 - 12000 10000 12000 12000 - 8000
1120 - 12000 10000 12000 12000 - 8000

* Continuous current rating of Types WE, VWE, VWVE, and WVE can be extended to 800 amps with an
accessory.
**The phase-trip protective accessory on electronic control will extend these interrupting ratings to the maximum
rated value.
TABLE 26
Cycle
Type % of Interrupting Rating Number of Unit Operations Maximum circuit
X/R Value
RXE 15-20 28 3
45-55 24 7
90-100 10 14
Total 62
WE 15-20 28 3
45-55 20 7
90-100 10 14
Total 58
VWE 15-20 112 3
45-55 80 7
90-100 40 14
Total 232
VWVE 15-20 56 3
45-55 40 7
90-100 20 14
Total 116
RVE 15-20 28 3
45-55 24 7
90-100 10 14
Total 62
WVE 15-20 28 3
45-55 20 7
90-100 10 14
Total 58

TABLE 27
Interrupting Ratings – Ground Trip
Interrupting Ratings
Minimum (rms symmetrical amps)
Trip Type RXE Type WE Type VWE Type Type RVE 400 Type WVE
Ratings 400 Amps 560 Amps Max * 560 Amps VWVE 560 Amps Max 560 Amps
369
 (amps) Max @ Max * Amps Max Max*
14.4 kV @ 4.8kV @ 14.4 @14.4kV @24.9kV @24.9-34.5kV @24.9-34.5kV
kV
25 3000** 3000** 3000** 3000** 3000** 3000** 3000**
35 4200** 4200** 4200** 4200** 4200** 4200** 4200**
50 6000 6000** 6000** 6000** 6000** 6000 6000**
70 6000 8400** 8400** 8400** 8400** 6000 8000
100 6000 12000** 10000 12000** 12000** 6000 8000

120 6000 12000 10000 12000 12000 6000 8000

140 6000 12000 10000 12000 12000 6000 8000
170 6000 12000 10000 12000 12000 6000 8000
200 6000 12000 10000 12000 12000 6000 8000
240 6000 12000 10000 12000 12000 6000 8000

280 6000 12000 10000 12000 12000 6000 8000

340 6000 12000 10000 12000 12000 6000 8000
400 6000 12000 10000 12000 12000 6000 8000
480 6000 12000 10000 12000 12000 6000 8000
560 6000 12000 10000 12000 12000 6000 8000

* Continuous current rating of Types WE, VWE, VWVE, and WVE can be extended to 800 amps with an
accessory.
**The phase-trip protective accessory on electronic control will extend these interrupting ratings to the maximum
rated value.

DIMENSIONS AND WEIGHTS

Diagram

For dimensions of reclosers with mountings, see Apparatus Catalog 280-85

Figure 11
DIMENSIONS OF TYPES RVE, RXE,VWE, VWVE, WE and WVE three-phase reclosers.

TABLE 28
Dimensions*
Recloser Type Without bushing current transformer accessory A (in.) B (in.)
RXE Standard or 17ʺ extra-creepage bushings 39½ 11
VWE 46½ 11⅛
WVE 40¼ 11⅛
RXE Standard bushings 42⅝ 11⅝
VWVE 49⅝ 11⅝
WVE 43⅜ 11⅝
370
 RXE 26½ ʺ extra-creepage bushings 44½ 12
VWVE 51½ 12
VWE 45¼ 12
With bushing current
Transformer accessory
RXE Standard or 17ʺ extra-creepage bushings 43⅞ 11¾
VWE 50⅞ 11⅞
WVE 44⅝ 11⅞
Standard bushings 47¼ 12½
54¼ 12½
48 12½
26½ ʺ extra-creepage bushings 49⅛ 12¾
56⅛ 12¾
49⅞ 12¾
Dimensions A and B are shown in Fig 11

TABLE 29
Weights and Oil Capacity
Recloser Type Weight oil * (lb) Oil Capacity (gal)
RVE 780 41
RXE 775 41
VWE 900 53
VWVE 900 53
WE 780 38
WVE 785 41
* Add 25lb for each bushing current transformer. Type ME electronic control weight is 60lb (single-size cabinet).
ZIMBABWE ELECTRICITY TRANSMISSION AND DISTRIBUTION COMPANY
FAULT REPORT No.: 2602 Form E86(a)
District……………………. Depot Code No: Date: Line construction

Name of Substation Supplying Feeder Feeder REF & Section No:

Type……………
1 Voltage at Fault KV 14 FOR LIGHTING DAMAGED TRANSFORMED ONLY:
2 Time of Interruption HRS Substation Name: Voltage Ration:
3 Time Reported HRS Transformer KVA
4 Time partially restored HRS Lighting Arrester Position: Not Fitted
5 Time fully restored HRS Line Side of isolator Load Side of Isolator
6 Maximum Duration of Interruption HRS D. Fuses Rating (Amps) Solid
15
7 EQUIPMENT OPERATED DESCRIPTION OF FAULTY AND ACTION TAKEN:
Type: Make:
No. Voltage
Rating Rip Setting
Section 8.9.10 refer to Section 7 only
8
No of Reclosing Operation: Available Occurred

9 Recloser Operation: Correct Incorrect N/A

10 Sectionallise Op: Correct incorrect N/A
11 Phases Affected Red Yellow Blue

IF PROTECTED OPERATION INCORRECT GIVE PROTECTION

DETAILS IN SECTIONS 12 and 13
12 OTHER ISOLATING GEAR WHICH OPERATE 16 WEATHER CONDITIONS
Type: Voltage SW No: Fine and Normal Cloudy
Prot Setting & CT Ratio: Hot Rain or Drizzle
13 OTHER ISOLATING GEAR WHICH FAILED TO OPERATE Cold Scattered Lightning
Type: Voltage SW No: Steady wind Severe Lightening
Prot Setting & CT Ratio: High Wind Other – (Specify)
17 SCHEDULE OF DAMAGED EQUIPMENT
Qty Make Type of Equip Serial No. Size Amp Voltage Details of Damage

371
18 TYPE OF LINE ON WHICH FAULT OCCURED 20 MONETARY OR SUSTAINED INTERRUPTION

33kv 010 22/11kv U.R 016 Monetary 301 Sustained 302

132KV 011 11Kv screened 017 21 DAMAGED MATERIAL (Insert Number X as indicated)

88Kv 012 11kv Underground 018 No of wood Poles 311 Recloser & Seat (x) 318
66KV 013 LV Overhead 019 No. of Arresters 312 Disconnects (x) 319
33Kv Screened 014 LV Underground 020 No. of “T” Formers 313 Cable Box/Joints (x) 320
19 33kv U.R 015 Service/Meter 021 Conductor (x) 314 U/ Ground Cable (x) 321
CAUSE OF FAULT Earthwire (x) 315 Meters 322
Lightning 201 Birds 208 Insulators (x) 316 Cts & VT 323
High Wind 202 Insects/Termites 209 Swgr.OCB’s (x) 317 Other Equipment 324
High Temperature 203 Animals / Reptiles 210 22 TYPE OF SUBSTATION AFFECTED
Rain or Flood 204 Grass Fire 211 For Lightning Damaged Transformers Only

Atmosph. Pollution 205 Corrosion 212 23 Terminal Sub 325 Underline Sub 326
Weathering & Deter 206 Dry rot 213 PROTECTION OPERATION
Trees 207 Unknown 214 Correct 331 Not Applicable 333
Mechanical Failure 261 Electrical Failure 262 Incorrect 332
Inadequate Precautions 271 Vandalism 274 Duration up to Partial No. of consumers
Restoration Affected
Electrical Overload 272 Outside Agency 275 Maximum Duration of No of Consumers
Interruption Affected
Switching Surge 273 Miscellaneous 276
ZESA Power Station 281 Cons Installation 283
Purchased Power 282

OPERATOR NETWORK MANAGER

372