ZAMBIA TANZANIA INTERCONNECTOR

PROJECT

11kV DISTRIBUTION LINES

TECHNICAL SPECIFICATIONS

Package 1 and 2

MARCH 2025

TECHNICAL SPECIFICATIONS

Page 1 of 52
CONTENTS

I Installation of 11kV OHL

II Wood Pole Supports
III Stays
IV Overhead Line Insulators
V Cross Arms
VI 11kV Overhead Line Construction Drawings

Page 2 of 52
 I. INSTALLATION OF 11KV OHL

Page 3 of 52
SPECIFICATION CONTENTS

DESCRIPTION ................................................................................................... PAGE NO

I. INSTALLATION OF 11KV OHL............................................................................ 3
1. SCOPE ........................................................................................................................ 8
2. GENERAL REQUIREMENTS ................................................................................ 9
3. MATERIAL - GENERAL....................................................................................... 18
4. CONSTRUCTION GENERAL .............................................................................. 21
5. ERECTION OF BARE CONDUCTOR LINES 11KV ........................................ 26
6. TESTING .................................................................................................................. 30
7. FORMS ..................................................................................................................... 31
II. WOOD POLE SUPPORTS ..................................................................................... 32
8. WOOD POLE SUPPORTS ..................................................................................... 34
9. TABLE OF WOOD POLES SIZES ....................................................................... 34
10. POLES....................................................................................................................... 35
III. STAYS ....................................................................................................................... 36
11. STAYS ....................................................................................................................... 38
12. APPLIED LOADS ................................................................................................... 38
13. TRANSVERSE LOADS .......................................................................................... 38
14. VERTICAL LOADS ................................................................................................ 38
15. LONGITUDINAL TERMINAL LOADS .............................................................. 39
16. SUPPORTS ............................................................................................................... 39
IV. OVERHEAD LINE INSULATORS ....................................................................... 40
17. GENERAL ................................................................................................................ 42
18. PIN INSULATORS FOR 11 KV LINES ............................................................... 42
19. TENSION INSULATORS FOR 11 KV LINES .................................................... 42
20. INSULATORS AND FITTINGS ............................................................................ 42
21. WITHSTAND FACTOR ......................................................................................... 42
22. FITTINGS................................................................................................................. 43
23. MARKING OF INSULATORS .............................................................................. 43
24. PORCELAIN INSULATORS ................................................................................. 43
25. INSULATOR CAPS AND PINS ............................................................................. 43
26. FERROUS METAL PARTS ................................................................................... 44
27. TENSION AND STRAIN INSULATORS ............................................................. 44

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28. SPINDLE .................................................................................................................. 45
V. CROSS ARMS.......................................................................................................... 45
VI. 11KV OVERHEAD LINE DRAWINGS ............................................................... 46

Page 5 of 52
 ABBREVIATIONS
ABC Aerial Bundle Conductor
ACSR Aluminium Conductor Steel Reinforced
Al Aluminium
BOQ Bill Of Quantities
BS British Standard ( a UK standards authority )
CNE Concentric Neutral and Earth cable
Cu Copper
DO fuse Drop Out fuse
HV High Voltage in this specification referring to the 11kV system
IEC International Electrotechnical Commission. An international (European)
Standards authority for electrical equipment
IPC International Standards Authority for equipment environmental protection
rating
ISO International Standards Organisation. A standards authority
kV Kilo Volt
LV Low Voltage in this specification referring to the 400V system
NEMA An American Standard
NRS Rationalised User Specification ( NRS project ) - a South African
Standards Authority
OHL Overhead Line
PG clamps Parallel Groove clamps
SA South Africa
SABS South African Bureau of Standards (a standard authority)
UV Ultra Violet

Page 6 of 52
 STANDARDS AND SPECIFICATIONS
The standards and specifications applicable and relevant to this specification in whole or in
part are as follows:
Overhead lines shall be erected in accordance with the specifications provided.
Table 1. Specifications, Standards and Codes of Practice
STANDARD/ DOCUMENTTITLE
SPECIFICATION
BS 0088 Fuses
BS 0215, Part 1 Aluminium Conductors
BS 0215, Part 2 Aluminium Conductors with Steel Rein forcing
BS 1872 Bushings
BS 2757 and IEC 85 Classification of Insulating materials Electrical Machinery and
Apparatus on the basis of Thermal Stability in service
BS 2914 and IEC 99-1 Surge Arresters
BS 3297 High Voltage Post Insulators
BS EN 792 Hot Dip (galvanised) Zinc Coatings
IEC 052 High-voltage testing
IEC 060 High Voltage Testing Techniques
IEC 129 Isolators
IEC 137 Bushings
IEC 270 High-Voltage Testing
SABS 0150 PVC Insulated Electric Cables and Flexible Cords
SABS 0177 Porcelain and Toughened Glass Insulators
SABS 0178 Non-current carrying Line Fittings for overhead Power Lines
SABS 0198 The selection, Handling and Installation of Electric Power Cable
of Rating not exceeding 33 kV
SABS 0679 Zinchromate Primer for Steel
SABS 0753 AND 05 Cross Arms
SABS 0833 Bushings
SABS 1035 and BS 223 High Voltage Bushings

Page 7 of 52
 1. SCOPE
1.1. SCOPE OF SPECIFICATION

Supports: Wood poles, 12 m, double

Conductors: Dog, ACSR
Insulators: silicone rubber, suspension/tension

This specification defines the general requirements for:-

 Erection of bare ACSR overhead lines, switchgear, distribution transformers,
fuses etc. associated works as required on the 11kV distribution systems.
1.2. ASSUMED EXTENT OF WORKS
For the purposes of this specification the following extent of works has been
assumed. The actual scope may vary as indicated in the tender document that
this specification forms part of. In the case where the scope in the tender
document and the technical schedules is in conflict with the assumptions in
this specification the contract requirements shall prevail. The scope of this
specification may change from time to time without prior notice. The
specification version however included with the tender document shall be the
legal document for the contract.
The assumed scope is:-
 The site survey of the overhead line routes for use in the Contractor’s detail
design.
 The supply of all sundry materials and equipment not provided by the
Employer required for the erection of the overhead lines, switchgear,
distribution pillars and all other items as required in the Specification and
Schedules.
 Taking Over from the Employer, delivery to site, erection, site testing and
setting to work in accordance with the manufacturer’s instructions the
equipment and materials as listed.
 Final route planning of the overhead lines, and site location of switchgears
and all other equipment together with the provision of the drawings for
wayleaves, municipal approval purposes and final records.
 The erection, site testing, setting to work and remedying of defects of the
items of work in accordance with the Specification and Schedules.
 The overhead line, distribution pillar and other equipment locations indicated
on the drawings are provisional and for Bid purposes only.
 The Contractor’s detail designs shall be submitted to the Project Manager for
approval.
 The Contractor must allow for all material, plant and labour required for the
supply and erection of the structures as indicated on the detail drawings and
as per the Bill of Quantities.
 Decommissioning of existing 11kV lines in the line route and installation of
new 11kV lines similar to the existing configurations.
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  Replacement of 11kV overhead lines with 11kV XLPE underground cables
complete with cable terminations and accessories where applicable for line
crossings (about 200m per crossing), unless the clearances are achieved in the
design for the higher voltage.

2. GENERAL REQUIREMENTS
2.1. SITE CONDITIONS
The site conditions for the 11kV lines scope shall be assumed to be as follows:
Item DESCRIPTION UNIT VALUE
1 Altitude of site above sea level m up to 1700

2 Ambient Temps:-
o
Maximum C 45
o
Minimum C -1
o
Shade (for cable rating purposes) C 30
o
Ground (for cable rating) C 20
3 Extreme Wind Speed m/s 28
Wind speed for OHL rating m/s 1.0
4 Isokeraunic Level days/ 86
year
5 Pollution Type Dust
6 Relative Humidity
Maximum % 80
Minimum % 39
7 Average Annual Rainfall mm 880
8 Hail Occasional
9 Sand Storms Occasional
10 Soil Thermal Resistivity Km/W 1.2
11 Max. Solar Radiation w/m2 1200

2.2. ELECTRICAL DESIGN DATA

Item Description Unit Nominal Voltage Level
33kV 11kV 0.4kV
1 Nominal system voltage phase kV 33 11 0.4
to phase
2 Highest system voltage kV 36 12 0,44
phase - phase
3 System Frequency Hz 50 50 50
4 Method of System Earthing Resist. Resist. Solid
(on 11 kV level E/C limited
1000 A)

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 Item Description Unit Nominal Voltage Level
33kV 11kV 0.4kV
4 Impulse withstand voltage -
(1.2/50 sec wave)
• Internal insulation kV 170 85
• External insulation, sea level peak 185 95
kV
peak
5 Power frequency withstand -
voltage 1 minute
• Internal insulation kV 70 28 2.5
peak 80 32
• External insulation, sea level kV
peak
6 Assumed highest switching N/A N/A -
surge
7 Substation clearances for
equipment not subject to
impulse tests mm 320 250 100
• Phase - earth mm 320 270 100
• Phase - phase mm 380 270 150
• Terminals across isolating
distance
8 Cable box clearances for fully
insulated shrouded terminals
Phase - earth mm 100 32 20
• Phase - phase mm 125 45 20
• Phase - earth over cable mm 250 125 25
surface
9 Transformers
Winding insulation Full Full
• Max flux density at any ratio T 1.8 1.8 -
or tap position
• Acceptable noise levels (1) dB 60 55
10 Insulation Distances for
Equipment, Bushings and
Insulators
• Min surface creepage mm 828 275
distance measured from live
metal to fixing base
• Min protected surface mm 289 97 -
creepage distance
• Min number of 254 mm dia 3 2 -
disc insulators in tension
strings
11 Surge Arresters
Min. rated voltage kV 39 15 -
• Nominal discharge current kA 10 10 -
(8/20 s)
• Class Distribution Min. 1.2 1.2 -
protective ratio

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2.3. OVERHEAD LINE CLEARANCES
Minimum Clearance from any point on or about the permanent equipment
where a person may be required to stand (measured from the position of the
feet).
Normal Operating To the nearest To the nearest part, not at
Voltage unscreened earth potential, of an insulator
live conductor supporting a live conductor.
in air. (m) (m)
not exceeding 15 kV 2.6 2.45
above 15kV but not 2.75 2.45
exceeding 33kV
above 33kV but not 3.0 2.45
exceeding 66kV
above 66kV but not 3.2 2.45
exceeding 88kV
above 88kV but not 3.6 2.45
exceeding 132kV
above 132kV but not 4.6 2.45
exceeding 275kV
above 275kV but not 5.3 2.45
exceeding 400kV
2.4. GROUND CLEARANCE
The following tables of conductor clearances are compatible with the existing
ZESCO practice and as provided for under the Energy Regulation Board
Code of Practice of 2022.

ROADWAYS
Normal Operating Over Road Other Areas except
Voltage between Line Vehicular Traffic where specified
Conductors (m)
Not exceeding 650 V 5.5 4.9
Over 650 V but not 5.8 5.2
exceeding 33 kV
Over 33 kV but not 6.1 6.1
exceeding 88 kV
Over 88 kV but not 6.7 6.7
exceeding 132 kV
Over 132 kV but not 7.0 7.0
exceeding 275 kV
Over 275 kV 7.3 7.3

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RAILWAYS

Nominal Operating Voltage between Line Min Height above Rail

Conductors (m)
Not exceeding 33 kV 7.65
Exceeding 33 kV but not exceeding 88 kV 7.95
Exceeding 88 kV but not exceeding 132 kV 8.55
Exceeding 132 kV but exceeding 275 kV 8.85
Exceeding 275 kV 9.15

2.5. OVERHEAD CONDUCTORS

BARE ACSR IEC 1089 (1991)
CODE Nominal Continuous Max SCC Used for
Name CSA Current for 1 sec
(mm2) Rating (A) (kA)
Gopher 25mm2 135 3.9 LV\11kV
Rabbit 50mm2 210 3.9 LV\11kV
Dog 100mm2 313 8.0 LV\11kV\33kV
Panther 200mm2 474 25.0 11kV\33kV\88kV
Bison 350mm2 659 27.5 33kV\88kV

Notes:
Assumptions for the continuous current rating:-
Item Factor
Maximum operating conductor temperature 80C
Operational conductor temperature 65C

2.6. XLPE CABLES 11 KV - 3 CONDUCTORS

The equipment and component supplied shall be in accordance with the latest
edition and amendments to, the following standards and specifications listed
below:

Standards Descriptions
IEC60502 Power cables with extruded insulation and their
accessories for rated voltages from 1 kV (Um =
1,2 kV) up to 30 kV (Um = 36 kV)

Page 12 of 52
 SANS (SABS) 1339 Electric cables - Cross-linked polyethylene
(XLPE) insulated cables for rated voltages 3,8/6,6
kV to 19/33 kV
IEC 60228 Conductors of Insulated Cables
IEC 60287 Electric cables - Calculation of the current rating
BS EN 60228 Conductors of Insulated Cables
BS-7870-4.20 Distribution cables with extruded insulation for
rated voltages of 11 kV to 33 kV- Three-core 11
kV cables
ASTM-D2843 Density of Smoke from the Burning or
Decomposition of Plastics
ASTM-D2863 Standard test method for measuring minimum
oxygen concentration to support candle - like
combustion of plastics (oxygen index)
IEC 60754 Test on gases evolved during combustion of
materials from cables
IEC 60332 Tests on electric and optical fibre cables under fire
conditions
IEC 60986 Short-circuit temperature limits of electric cables
with rated voltages from 6 kV (Um = 7,2 kV) up
to 30 kV (Um = 36 kV)
SANS(SABS) 6284 Test methods for cross-linked polyethylene
(XLPE) insulated electric cables
SANS(SABS) 6282 Test methods for bare conductors and conductors
of insulated electric cables
SANS (SABS) 1411-6 Materials of Insulated electric cables and flexible
cords
SANS(SABS) 6286 Test methods for sheathing of insulated electric
cables
SANS(SABS) 6291 Partial discharge measurements on power cables
SANS(SABS) 60754 Test on gases evolved during combustion of
materials from cables
SANS(SABS) 60332 Tests on electric and optical fibre cables under fire
conditions

• All cables shall be suitable for high ambient, Zambian Climatic conditions. Cables
shall be designed to withstand the mechanical, electrical, and thermal stresses
under the unforeseen steady state and transient conditions and shall be suitable
for proposed method of installation.
• Any material used on the cable should not be hygroscopic.
• Works Contractor to submit Manufacturers' complete cable technical
specification with bid. Values of parameters to be given for both in air and direct
burial underground.
• Conductor shall be of uniform, of good quality, free from defects Aluminium
copper.
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 • Insulation shall be Cross Linked Polyethylene (XLPE).
• Conductor screen and insulation screen shall both be extruded, semiconducting
compound and shall be applied along-with XLPE insulation in a single operation
by triple extrusion process. Method of curing for 11 kV and 3.3 kV cables it shall
be "Dry curing/ gas curing / Steam curing".
• Extruded Semi-conducting screening and metallic screening of copper tape shall
be generally as per IEC60502 (Part-II) with latest amendments. The semi
conducting compound shall be suitable for the operating temperature of the cable
and compatible with the insulating material.
• The insulation screen shall be an extruded layer of black semi-conducting
compound and continuously covers the whole area of insulation. The semi-
conducting screens should be effectively cross linked to achieve 90 ᵒ C cable
rating. The contact surface between insulation and insulation screen shall be
smooth and free from protrusion and irregularities.
• The interface between insulation and insulation screen shall be free of any voids.
Insulation screen shall be strippable type.
• Armouring - Material for armour for Single Core Cable shall be Aluminium wire.
• Armouring shall be as per relevant IEC and it shall have minimum 90% coverage.
• Breaking Load of the joints shall be minimum 95% of the normal armour.
• Acid Gas Generation - Max 20% (as per IEC 60754-1)
• Smoke density rating: 60% (As per ASTMD 2843)
• As per IEC 60332 part-3 (Category B)

Minimum bending radius shall be 10 D. Repaired cables shall not be

acceptable.
The operating voltage for earthed systems in this specification (defined by the
relationship U0/U (Um) recognized for the purposes of the standard) shall be
6.35/11 (12) kV.

U0: is the rated power frequency voltage between conductor and earth or
metal screen for which the cable is designed,
U: is the rated power frequency voltage between conductors for which
the cable is designed, Um: is the maximum value of the "highest system
voltage" for which the equipment may be used.

The type of insulating compound in this specification shall be Cross-linked

Polyethylene (XLPE). The conductor shall be copper circular, stranded and
compacted to Class 2. The conductor size shall be 185mmsq. The maximum
sustained conductor temperature including the sheathing compound shall be 90 °C.
The thickness of the conductor screen shall be as per SANS (SABS) 1339. The
resistivity of the conductor screen shall as per SANS (SABS) 1339.

Page 14 of 52
 • The termination and jointing kits shall be designed and manufactured to IEC
61442 and shall be heat shrinkable material suitable for use in terminating and
jointing XLPE cables having aluminium or copper stranded conductors.
• The components included in this specifications are for use in power cable
terminations and cable joints used on non-effectively earthed electrical systems
having a normal working voltage of 6.35/11 (12) kV.
• Joints and terminations shall be designed to carry any thermal and mechanical
forces will be developed during maximum three-phase faults currents
symmetrical and asymmetrical.
• Assembled components forming part of a cable system shall be capable of
operating under the normal and fault temperature conditions specified in the
relevant cable specifications.
• The termination and joints kits shall be complete with all components and
materials necessary for terminating and jointing of specified cable type and size.
• The jointing / termination system shall be designed to provide an easily
constructed and clearly understood method of installation. Key components shall
be available in a spare parts list.
• The components and materials for each category of termination and jointing kits
shall include the minimum following items: a. XLPE Joint:
i. Internal
insulation tubing
ii. Stress
control tubing iii.
Anti-track
tubing iv.
External
protective tubing
v. Compression and mechanical connectors for the
appropriate size of cable
vi. Sufficient duty earth strip/ wire gauze for earth continuity
vii. Constant tension clips
b. XLPE Termination:
i. Insulation
tubing ii.
Stress
control tubing iii.
Anti-track
tubing iv.
External
protective tubing
v. Compression and mechanical connectors for the
appropriate size of cable vi. Clear oil barrier tubing
vii. Resin that melts to cover voids and deter
moisture ingress viii. Sufficient duty earth strip

Page 15 of 52
 ix. Constant tension clips (earth
connection) x. Cable
breakout to separate cores
• The jointing and termination kits shall be designed and manufactured to ensure
that all components and materials shall be weather-resistant and suitable for use
in the atmospheric conditions of Zambia stated.
• The termination and jointing kits shall be free from defects that would likely cause
them to be unsatisfactory in service. The use of tapes to provide primary
insulation, screening, or stress control is not acceptable.
• The components and materials shall be manufactured to ensure high moisture
sealing capacity, resistance to fungal and insect attack, proper stress control, and
resistance tracking when in service.

2.7. SUPERVISION
All work on site shall be supervised by a sufficient number of representatives
of the Contractor who are fully experienced in work of the type covered by
the Specification.
2.8. RESPONSIBILITY OF CONTRACTOR
Before any of the Contract Works are made alive the Contractor shall satisfy
the Project Manager that any connections between the Contract Works and
other plant or apparatus are correct.
2.9. QUALITY OF MATERIAL
Only new and unused material of superior quality may be used. All materials
shall, where relevant comply with the applicable Standard and specification.
It should be noted that all materials supplied under this contract as being IEC,
BS or SABS approved shall bear the relevant approving body mark unless no
such mark is applicable for a specific item.
2.10. STANDARD OF WORKMANSHIP
The electrical installation of this contract must be carried out by qualified
electricians and cable jointers in accordance with the best modern methods.
The Project Manager reserves the right to reject any work which, in his
opinion, is not completed in a neat and orderly fashion and in accordance with
accepted practice.
2.11. WAYLEAVES AND ACCESS TO SITE
Wayleaves and access facilities subject to the requirements of landowners and
occupiers and subject to the provisions below will be provided by the
Employer to enable the Contractor to carry out the erection of the Works but
such facilities will not include facilities for storing material. The necessary
agreements for both the removal of obstructions such as trees and pipes and
for the removal or guarding of telephone and power lines will be arranged by
the Employer.
The Contractor shall, at his own expense, do what is necessary to make every
access suitable for his use and shall take all reasonable precautions to avoid
damage to land, property, roads, crops, field drains, fences, walls, hedges,
gates and the like and shall ensure that the work is adequately supervised so

Page 16 of 52
 that damage is reduced to the minimum. The Contractor will be liable for all
damage arising by or in consequence of the works except damage to crops
and shall pay compensation or make good at the option of the Employer. The
Contractor shall dispose of all spoil and surplus material after erection.
The Contractor shall at all times keep sites free from obstruction, waste
materials and rubbish and shall remove from the sites at his own expense all
surplus materials and temporary works as soon as they are no longer required
for the erection of the Works. On completion of the Works, the Contractor
shall leave the sites clean and in a workmanlike condition to the satisfaction
of the Project Manager.
The Contractor shall be responsible for maintaining agreed access routes,
without undue widening, in a usable condition for the duration of the Contract
and the wayleave grantor shall not be put to any inconvenience in gaining
access to his land or buildings and no unauthorised access route shall be taken
by the Contractor.
Adequate provision shall be made by the Contractor to prevent the straying
of, or damage to, livestock during the execution of the Works and until the
permanent reinstatement of fences, walls, hedges, gates and the like is
completed.
The Contractor shall be liable for any damage to or loss of livestock due, in
the opinion of the Project Manager, to failure to comply with the above
requirements.
By the date for access to the overhead line and underground cable routes
stated by the Contractor in his Master Programme, the Employer shall
(subject to the Contractor being then ready to commence work) provide over
the whole length of the routes such right of access for the Contractor’s staff
to carry out survey work, investigation of the general foundation conditions,
construction, testing and commissioning of the required Works in accordance
with the Specification.
The Contractor shall make all necessary arrangements (other than questions
of wayleaves and access) with the occupiers of the routes, but if any difficulty
shall arise the Contractor shall inform the Project Manager thereof. The
Project Manager shall thereupon take such steps as may be necessary to
resolve the difficulty.
The Contractor shall make any necessary arrangements and take any
necessary precautions where the routes cross roads, tele-communication lines
or cables, buildings, power lines or cables, orchards, gardens, or other
obstacles or ground over which erection cannot be carried out in the normal
manner. The Contractor shall provide all necessary temporary works to
overcome the obstacles and shall comply with all reasonable requirements of
the Authorities concerned.
The Contractor shall give the Project Manager at least 14 days notice of his
intention to install any service connection, to enable the Employer to make
the necessary arrangements for access to the consumer’s premises.
2.12. TREES
No trees shall be damaged, cut or pruned during the execution of the contract
unless specifically authorised by the owner of the stand/s nearest to the tree.

Page 17 of 52
 Should any trees have to be removed by the Contractor he shall arrange for
the complete uprooting and trimming of tree trunks as well as the stacking of
all trunks and branches. Holes caused by the uprooting shall be filled and
consolidated. Rubble shall be removed to leave the site neat and tidy. The
Contractor shall be held responsible for any damage which may occur during
the felling of trees.
Where trees are to be pruned, this shall be done neatly to the satisfaction of
the Project Manager.
2.13. EQUIPMENT NUMBERING
2.13.1. Numbering system
All major equipment such as switchgears, Sectionalisers, etc. as well as poles
shall be numbered. The numbering system shall be provided by the employer.
In the case where the employer does not have a suitable system the contractor
shall propose a system to be used.
The numbering system shall be agreed during the contract stage.
In general the pole numbering system shall be of such a nature as to reference
poles to the feeder and substation.
Transformer structures shall be identified by means of a similar unique zone
identification number.
2.13.2. Numbering method

All the marking tags shall be fastened on the equipment side facing the road
where applicable or shall face in the same direction where a road does not
exist alongside the overhead line.
This labelling must be done in the form of permanent letters using a stencil
and permanent, durable good quality spray paint. The height of the letters
must be at least 5 cm. and shall be clearly visible from ground level
The pole numbers will be black on a yellow background 50mm x 50mm. The
text will be thick, 25mm high numbers nailed to the pole 3500mm above
ground level facing the road.
In general these numbers shall be as indicated on the drawings but before
manufacture thereof, confirmation of the final numbers must be obtained
from the Project Manager.
The materials used for the numbering shall have a design life, matching that
of the equipment it is accompanying.
.
3. MATERIAL - GENERAL
3.1. ACSR-CONDUCTORS AND FITTINGS
ACSR-conductors to IEC1089 shall be used for overhead lines. The cross-
sectional area shall comply with the Detail Technical Specification.
The conductors shall be attached to the insulators by pre-formed ties or
compression fittings, in the case of sets of tension insulators. Double
distribution ties shall be used at each pin insulator for conductors over 50mm2
cross-section.

Page 18 of 52
3.2. CONDUCTOR ACCESSORIES AND FITTINGS FOR ACSR
CONDUCTOR
The following fittings shall be used with ACSR-conductor:
(a) Clamps
In all cases the clamps used for T-offs and jumper connections shall be a
Parallel Groove clamps (P.G. Clamps) suitable and rated for the particular
conductor. Non-oxide grease shall be used to prevent corrosive electro-
chemical reactions.
(b) Suspension Attachment
In all cases the conductor shall be attached to intermediate post and pin
insulators by means of an aluminium alloy wraplock tie suitable for the
particular conductor. It is important to note that the installation of a standard
neoprene sleeve which will prevent shaving of the conductor against the
insulator is a specific requirement.
(c) Strain Attachment (Dead Ends)
The Strain attachment shall consist of an aluminium alloy pre-formed dead
end and hot dipped galvanised thimble (open pattern). The pre-formed dead
end shall be attached to the strain insulator by means of a hot dipped
galvanised shackle.
3.3. JOINTS
Compression or automatic joint assemblies for conductors shall have a joint
sleeve for the steel core and also for the aluminium portion. They shall be
suitable to be used with modern types of compression dies. Joints using anti
corrosive preservatives are preferred. A quantity necessary for the erection of
the line as well as caulking guns shall be included in miscellaneous
accessories for this tender.
No joints in conductors shall be allowed in spans crossing streets, roads,
railway lines or telephone services.
3.4. REPAIR SLEEVES
These shall be of the compression type, sized correctly and of correct material
to be used with corresponding conductors.
3.5. INSULATORS AND FITTINGS
Great care shall be exercised when fitting insulators and components.
Insulators shall be chosen to provide the mechanical strength and insulation
level required by the line at every point. These may be: pin, line post, strain
or suspension type.
Insulators shall be spaced to provide the conductor clearance required.
Composite insulators and their pins complying with relevant standards shall
be used in straight line intermediate positions.
Disc or long-rod insulators shall be used in all strain, tension or angle
positions. Clevis-and-tongue or ball-and-socket type insulators complying
with BS3288 shall be used. Disc insulators may be of glass or porcelain.
Curved wood pole washers shall be fitted between the collars of insulator pins
and the cross-arm or pole and between the pin nut and the cross-arm or the
pole.

Page 19 of 52
 Insulators hooks shall be of an approved pattern and shall be manufactured
from BS 4360 grade 43 mild steel or forged.
Terminating and yoke straps shall be manufactured from BS 4360 grade 43
steel or forged to an approved design.
All steel or ironwork i.e. fittings, bolts, nuts, washers, etc., shall be hot dip
galvanised.
3.6. LINE POST INSULATORS
Mounting of the line post insulator units shall be by means of galvanised steel
M20 spindles, washers and locked nuts. Spindles shall have collars to prevent
stripping of the insulator threads during installation
All insulators shall be marked clearly and permanently with the
manufacturers name, the type and the date of manufacture.
3.7. LINKS
Links shall be provided within the MV rings positioned as shown on the
layout drawings. Line links shall be three single phase units to be operated by
means of a link stick.
The three single phase units shall be bolted to a sturdy "U" channel or cross
arm which in turn shall be clamped to the pole by means of two "U" bolts. All
metallic parts shall be hot dip galvanised after cutting, drilling and welding.
3.8. DROP OUT FUSES (DO'S)
These units shall be installed, one span away from where the line Tees-off
from the existing line.
Drop out fuses shall be rated as per schedule of material and shall be so
installed to ensure that melting of the fuse elements leads to the cut out link
being expelled from the line contacts.
Drop out fuses shall also be installed as indicated on the construction drawing
if such a drawing is provided in the Contract. In the case of the contractor
providing construction drawings the DO fuses shall be clearly indicated.
3.9. SURGE ARRESTERS
Surge arresters will be installed at the following places:-
a) All transformer 11kV sides and the 11kV incoming lines.
b) Incoming and outgoing side of a four pole structure.
c) Both sides of sectionalisers.
3.10. LINE DISCONNECTOR
Three-phase line disconnector, of the solid link type, shall be provided at all
points shown on the drawings.
The disconnector shall have insulators manufactured from vandal-resistant
Cycloalephatic resin filled with silanised silica, and shall be mounted on
galvanised steel cross-arms as indicated on the relevant drawings.
The actuator in question shall operate, causing all three links to operate via a
common operating shaft, thus isolating the secondary circuit.

Page 20 of 52
 4. CONSTRUCTION GENERAL
4.1. FOUNDATIONS, EXCAVATIONS AND BACKFILLING
The detail design of support foundations, where applicable, shall be submitted
to the Project Manager together with load calculations. It is the Contractor's
responsibility to do soil tests in order to establish load bearing and chemical
properties of the soil along the route.
All pole and stay excavations shall be 1 metre wide, 1.5 metre long and for
stays only have a depth of 1.5m : other dimensions shall correspond to the
specified pole planting depth.
If the ground structure does not permit deep excavation due to hard rock, a
concrete foundation of one cubic meter and minimum depth of 750mm shall
be provided or rock drills shall be used whichever method is approved.
Backfilling shall be carried out so that the material is properly consolidated
in layers of uncompacted thickness not exceeding 150mm. Each layer shall
be thoroughly compacted before the placement of the next layer
In sandy, other loose soil or marshy ground, cement or concrete shall be used
for consolidation and strength increases. No casting of concrete will be
allowed in wet soil.
All remaining material excavated, and not used for backfilling, shall be
removed from site.
Blasting shall not be permitted without the consent of the employer. It is
envisaged that it would rarely be used in special occasions.
All steel work below ground shall be galvanised. Steel work cast into concrete
shall be securely keyed.
The finish on foundations shall be smooth and neat, sloped to the outside to
ensure that no water shall assemble on top of foundations.

4.2. WOODEN POLE INSTALLATION

Wooden Poles shall be used throughout and shall be of the appropriate length.
The design and construction of structures shall comply in all respects with
internationally accepted safety factors.
During planting, all measurements shall be taken on that section of structure
protruding above ground level.
Poles, matching in appearance, length, diameter and straightness shall be used
in the construction of all two- pole and/or four-pole structures.
The standard of workmanship and accuracy of manufacture shall be such that
easy erection on site is guaranteed.

As guideline, Spans longer than 100m must be done using H-pole structures
for strength of the structure as well as better conductor clearance. Any long
stretches of intermediate poles must have a supported strain structure every 0.5 km.

4.2.1. Pole Dimensions

The pole dimensions listed in the table below shall be used. Poles not
complying with these dimensions shall be removed from site.
Page 21 of 52
 Table 2. Pole sizes
Pole Classificati Top Dia in Min Dia System usage
Length on mm 1.5m from
in min -max the Butt mm
Meters
7 Light 125-150 200 LV
7 Medium 140-170 200 LV
9 Light 125-150 180 LV
9 Medium 150-180 220 LV & 11kV
9 Stout 190-240 275 11kV & 33kV
10 Light 125-160 185 LV
10 Medium 150-180 230 LV & 11kV
10 Stout 190-245 285 11kV & 33kV
11 Light 125-160 195 LV
11 Medium 150-190 240 LV.Dual.& 11kV
11 Stout 190-250 295 11kV & 33kV
12 Light 125-165 200 LV
12 Medium 150-190 250 LV & 11kV
12 Stout 190-250 305 11kV & 33kV
14 Medium 160-205 260 LV & 11kV
14 Stout 195-255 335 11kV,33kV
16 Medium 170-215 305 11kV
16 Stout 200-265 365 11kV,33kV.

4.2.2. Pole Planting Depth

Poles shall be planted at the following minimum depths:
Table 3. Pole Planting Depth
Length (m) Planting depth (m)
5 1
7 1.2
9 1.5
10 1.6
11 1.8
12 2.0
14 2.3

Page 22 of 52
 Length (m) Planting depth (m)
16 2.6
Generally poles shall be planted in general not less than 1/6 of the pole length.
4.2.3. Installation of Poles
Poles shall be erected vertically plump, in line and sufficiently stayed to
maintain that position. The contractor shall employ suitable instruments to
ensure this
After erection, poles shall be thoroughly cleaned from all foreign material.
Kicking blocks shall be provided where ground with poor bearing qualities is
encountered.
All stay and pole holes shall be back-filled as specified in this specification.
Where so indicated, the soil shall be stabilised by the addition of a mixture of
cement in the ratio of 1:10 by volume.
Poles shall not be installed in clay soil or in swampy conditions without the
necessary precautions to stabilise the installation.
Excavations must be cleared of loose soil so that the butt end of the pole will
be resting on undisturbed soil. Generally, poles and stays shall be resting in
undisturbed soil.
If unsatisfactory conditions for the installation of poles and stays are
encountered during the excavations, the Project Manager shall be informed
without delay in order to facilitate alteration of the foundation design or
alteration of the route of the line.
If wooden poles are installed in a concrete, or other water retaining
foundation, the poles shall protrude through the concrete to ensure adequate
natural drainage to prevent rotting of the wooden poles in the foundation due
to the accumulation of water between the poles and the foundation.
4.2.4. Pole Spacing
If the spacing of the poles is not specified in the Detail technical Specification,
poles for 11kV line shall be spaced 100 m apart.
4.2.5. Mounting of cross arms
All cross-arms shall be mounted horizontal and in a proper fashion and at the
correct distance from the top of the pole.
4.2.6. Pole Drilling
As far as possible the drilling of poles must be avoided.
Poles will not be pre-drilled and insulator pin holes, etc., shall be drilled using
a template centrally disposed on the main diameter of the pole or cross-arm
and drilled truly vertically in both the transverse and longitudinal directions
of the line.
All holes drilled on site in wood crossarms or poles shall be properly treated
and coated with a mixture of creosote and tar and unused holes shall be
plugged.
4.2.7. Miscellaneous
H-pole structures shall be square and symmetrical.
Coach screws are to be installed where required i.e. below stay pole wraps.
Page 23 of 52
 All U-bolts and backstraps are to be fitted correctly.
All preforms are to be correctly wrapped.
4.3. STAYS
Where conductors terminate, or where the line deviates by more than 10 or
where shown on the drawings, normal 45 stays must be supplied to anchor
the poles. These stays shall consist of stayrods together with base plates.
Staywire shall be as per schedule of materials and furthermore stay insulators
guy grips, and pole top make offs are required.
Stays must be properly installed so that the stayed poles are vertical after
tensioning of the conductors.
Where normal stays cannot be installed and after approval by the Project
Manager use shall be made of struts. These struts shall comply with the
requirements for the specific type of wood pole and shall be selected to match
the line pole to which they are attached. The attachment of the strut to the line
pole shall be as shown on the drawings.
Alternatively in certain cases as shown on the drawings or after approval by
the Project Manager use may be made of a flying stay or short stay. This detail
will be supplied on request.
Where conductor brackets or cables etc. are attached to the wood poles such
attachments shall preferably be done with stainless steel strapping.
Prop-stays (struts) will only be permitted with the approval by the Project
Manager.
Stays shall be provided at all line terminations, angle poles, at tension poles
and at all road/rail crossings.
Where stays are to be erected within any residential property, short-stays shall
be used unless the stay is located directly on the boundary between two
houses. Alternatively, approval may be obtained for stub-stays.
Stays shall be installed at an angle of 45 to the horizontal, except where this
is not feasible due to external factors.
Stays shall be covered with an easily visible red painted steel pipe where the
stay present a hazard to passing traffic.
Complete stay assemblies comprising rods of at least 20 mm diameter and
2.4m long, turnbuckles, thimbles, washers and BS pattern 2 base plates at
least 450mm x 450mm shall be installed. Sufficient margin (at least 200mm)
for future adjustment of the turnbuckle shall be provided.
Stay rods shall be planted to a vertical depth of at least 1.5m. The hole shall
allow the rod and plate to be installed at the correct angle, and the base plate
shall be against undisturbed ground.
The stay plates shall be galvanised and reinforced and provided with a washer
of sufficient strength to ensure that the load is evenly spread over the plate
without deformation.
Should it become apparent that a stay, if erected in accordance with the
drawings, would require the stay rod and plate to be buried in yielding or
suspect ground the contractor shall propose an alternative method and
approval shall be obtained from the Project Manager.

Page 24 of 52
 Stays in rock may be drilled and grouted.
During backfilling, the material shall be properly consolidated.
In sandy or other loose soil or marshy ground, cement or concrete shall be
used for consolidation and increased strength.
Stay rods shall not be bent.
Stays shall be erected in line with the conductors at angle poles to cater for
pulls in both directions, or as indicated on drawings.
Approved "Pre-formed" line products may be used for anchors and other
applications, and shall be looped round the pole top, held in position by long
coach screws, and be wound around the main stay wire as specified by the
manufacturer.
"Crossby" clamps will not be permitted on final installations.
Porcelain stay insulators shall be installed in the stay wire as high as possible
above ground level but far enough away from the structure to ensure that the
portion of the stay below the insulator does not become alive.
Stay wire make-offs shall be painted with bitumastic paint on completion.
4.4. SPAN LENGTHS
The ruling line span length shall be as stated, and represents the mean
horizontal distance between all standard height poles over level ground.
Deviations in the length of spans from the ruling span length shall be first
submitted for approval prior to construction.
4.5. ANTI-CLIMBING GUARDING
Anti-climbing device shall be provided on all prop-stays (struts), overhead
links or drop-out fuses, at a height of 2m up to 3m above ground level. Where
barbed wire is used as anti-climb guarding, the wire shall be galvanised, the
coils shall be laid neatly and parallel to each other, and shall be fixed to the
pole at 90mm intervals with staples.
Where two or more stay wires are installed parallel to each other, anti-
climbing guarding shall be provided on both wires from a height of 2m to 3m
above ground level.
4.6. NUTS AND BOLTS
Bolts, nuts and washers shall be made of steel, and shall be galvanised. Nuts
and bolts shall have hexagonal heads. Bolts shall not be cut after
galvanisation. Rods cut on site shall be treated with corrosion resistant paint.
No electrochemical reaction or corrosion shall result where nuts and bolts are
in contact with non-ferrous materials.
Nuts shall be properly locked.
Lock-nuts shall be used on components subject to vibration.
Bolts and studs shall protrude at least at 5mm beyond the final nut, but shall
not be unnecessarily long.
All bolts used in the structure assembly shall be provided with washers at the
bolt head and at the nut.
Curved washers shall be used wherever nuts or bolts are in contact with
rounded wood surfaces.

Page 25 of 52
4.7. SETTING OUT PEGGING AND POSITIONING
Poles at street corners and intersections shall be set out to line up with the
poles in the adjacent street in order to provide perpendicular street crossings.
Remaining structures shall be placed in between these fixed structures to
conform as closely as possible to the required average spacing.
Intermediate pole structures shall, as far as it is practically possible, be
positioned equally distanced between terminal and angle structures.
Due cognisance of existing entrances, driveways, structures etc. shall be taken
in the positioning of pole structures.
The Contractor shall be responsible for the survey of the line routes as shown
on the reticulation layout drawings.
The Contractor shall inform the Project Manager, in writing, where deviations
form the planned routes are deemed necessary because of physical or other
obstructions.
The Contractor shall be responsible for the measurement and pegging of all
pole structures, stay and strut positions. All structure positions shall be
pegged prior to erection.
4.8. CLEARANCES
Clearances shall be as per the Employer Standard Specification.
Where power conductor must cross a telephone line double pin insulator
construction shall be used and vertical clearances shall be in accordance with
the relevant ZESCO Standard Specification or ERB Wayleave Code of
Practice of 2022.
4.9. CROSSINGS
All crossings shall be co-ordinated with the departments concerned.
Care shall be taken not to disturb existing telephone services.
Road and rail crossings shall be co-ordinated with the concerned authorities.
The local traffic department shall be notified prior to stringing and
precautions shall be taken not to endanger any road or rail transport action.
4.10. STRINGING OF CONDUCTORS
If possible the complete drum length shall be used on spans without the
necessity of cutting and rejoining. Joints shall only be allowed in sections not
crossing other public services such as rail, road, communications lines or
other power lines.
Should any doubt exist as to whether the conductor has been erected and/or
tensioned correctly the suppliers will be required to give their verdict and if
necessary the Contractor shall restring the conductor. Any conductor
damaged during stringing will have to be replaced at the Contractor's own
expense.
4.11. ELECTRICAL BONDING
Metal components within 50mm of each other shall be bonded together as a
precaution to reduce television and radio interference.

5. ERECTION OF BARE CONDUCTOR LINES 11KV

In general all relevant requirements stated in the previous sections shall apply.
Page 26 of 52
5.1. HANDLING OF THE BARE CONDUCTOR
The Contractor shall ensure that the conductor is not damaged during
installation and dragging of the conductor across the ground will not be
allowed.
5.2. CONDUCTOR CLEARANCES
The minimum conductor to ground clearances as stipulated in this
Specification shall be closely observed. Allowance shall be made for
conductor creepage and subsequent increased sag after a period.
The Contractor should note that in all cases clearances as per the specification
shall be applied to this installation and should be measured and the
appropriate form(s) completed.

5.3. CONDUCTOR SPACING

The minimum conductor spacing are:
Table 4. Minimum Conductor Spacing
Pole Conductor Spacing (mm) for Supply voltage of :-
Spacing (m)
0.23/0.4 11kV 33kV
kV
60 300 600
70 300 600
80 360 700
90 400 750 800
100 800 1100
110 820 1200
120 850 1500

5.4. ROAD CROSSINGS

The Contractor should note that at road crossings no special arrangements
will be required other than to ensure that structures on either sides of the
crossings are strain structures, properly stayed and fitted with either pistol
grips or arching horns.
5.5. SPANS SAGS AND STRAINING
The equivalent span of a strain length is given by the following formula :

Page 27 of 52
 (Leg)2 = (L1)3 + ... + (Ln)3
(L1 + L2 + ... + Ln)
Where : n = number of spans,
and Ln = the length of the nth span
The corresponding sag (S) of span with length L within the above strain
section shall be :
S = [(L)2 x Seq]/(Leg)2
The sag for an equivalent span length (Seq) shall be determined from the sag
chart for particular temperatures.
In case of very long strain sections these shall be strained in sections
consisting of 3 to 5 spans each. In this case the conductor shall be temporarily
anchored on the next structure adjacent to the concerned sub-strain section.
This pole shall be temporarily stayed if it is of the suspension type.
Suitable temporary arrangements for the staying of structures wherever
necessary, shall be made and such arrangements shall not impose overload
conditions on any portion of such structures. The cost of the provision and
labour of temporary stays shall be included in the tender price.
Extensive care shall be exercised when stringing, tensioning, clamping and
jointing of conductors that individual strands are subjected to the same forces
and the same movements as all other strands in that cross section, i.e. no
deformation of conductors by means of over-tensioning of individual strands
or bird caging of strands will be allowed. Auxiliary and temporary clamps or
handling devices used for erection purpose shall also be such that relative
movement of conductor strands is prevented.
When straining conductors, the equivalent span length method shall be used
with regard to the appropriate sag of each span length.
All equipment used for stringing such as sag charts and dynamometers shall
be in good condition and recently calibrated.
The temperature reading shall be taken in a 2m section of conductor where a
section of the core has been removed. The temperature shall be taken with the
thermometer inserted into the centre of the conductor and the conductor
positioned at cross arm height of the concerned strain section. The actual
reading shall be taken only after 2 hours and the time of temperature reading
and tensioning must be as close as possible.
A record shall be established giving reading of temperature, tension and sag
and their time of measurement for each strain section.
Manufacturer’s stringing and tensioning charts shall be used to erect
conductors. Conductors shall not be tensioned to more than 25 % of the
breaking strength of the conductor at -5.5 C with no wind.
All the conductors of the same line shall be tensioned simultaneously using
suitably rated chain-ratchet pullers and “come-alongs” specially designed for
the particular conductor.
Conductors shall be pre- stressed for not less than one hour before binding-
in.

Page 28 of 52
 Dynamometers, which shall be re-calibrated if so directed, shall be used only
for the initial tensioning of the conductors, the final regulation being carried
out by setting the conductors to correct sag.
5.6. ATTACHMENT OF INSULATORS AND HARDWARE
Insulators, strain and suspension hardware shall be secured to the structures
in accordance with the manufacturer’s instructions shown on the drawings.
Broken, cracked, scratched or chipped will not be accepted. All insulators
must be thoroughly cleaned before installation.
All split pins, security clips, locknuts or other locking devices shall be applied
in their intended manner of use, so as to prevent uncoupling of the items in
service.
5.7. STRINGING OF CONDUCTORS
The fullest possible use shall be made of the minimum conductor lengths
available in order to reduce the wastage of conductor.
The fullest possible use shall be made of the maximum conductor lengths
available in order to reduce the number of joints in the conductor to a
minimum.
It must be noted that no joints are permitted in spans where the line crosses
any proclaimed line or land.
The conductors, joints and clamps shall be erected in such a manner that no
bird-caging, over tensioning of individual strands or layers of the conductor
or other deformation of the strands or the complete conductor shall occur.
Conductors shall be run out and tensioned in such a manner as to reduce
contact with the ground or other obstruction to an absolute minimum. In
particular, under no circumstances shall the conductor be allowed to touch or
be dragged across stony ground, fences or other objects liable to damage the
conductor strands.
The conductor shall not be allowed to rub on any part of the structure, but
shall be placed in suitable aluminium jockey pulleys (neoprene lined) which
shall be designed to impose the smallest possible restraint on the free
movement of the conductor.
When running out conductor, the drums shall be supported on approved drum
jacks. Suitable means shall be used to prevent drum “ over-run”. Under no
circumstances shall conductor be run out from drums laid on a drum cheek,
as this would kink the conductor as it is pulled over the free cheek .
5.8. CONDUCTOR JOINTS AND TERMINATIONS
Midspan joints shall be kept to a minimum and where unavoidable, shall be
made with approved full tension line splices.
Where preformed helical armour rods, splices, dead-ends and stay make-offs
are used, extreme care shall be exercised in the handling and storage of these
items. It shall be stored in their original packing, under cover, until actually
used. When being installed, care shall be taken that abrasive grit is not lost
through mishandling.
It is a specific requirement that midspan joints shall only be made by a person
tested and certified as being competent to do such joints by either the
Contractor, Employer or the supplier of the joint.

Page 29 of 52
 Where phases are to be interconnected double “P.G.” clamps of a suitable size
shall be used.
All joints of conductors and earth wires shall be recorded and their exact
position indicated.
Trails and bridge wires must be neatly disposed and connected with clamps
or line taps with a minimum of two per connection or by means of other
approved mechanical connectors.
5.9. TOOLS AND EQUIPMENT
It must be noted that handling equipment of any sort which has previously
been used for the handling and erection of copper conductor shall under no
circumstances be used for the handling and erection of aluminium based
conductors, and vice versa.
The following tools (minimum per team) shall be provided by the Contractor
and shall be inspected and approved by the Project Manager before
construction commences:
1. Chain lever hoist
2. Come-alongs
3. Dynamometer
4. Thermometer
5. Ladders
If the Project Manager finds the equipment and tools for installation to be
unsuitable he will issue an instruction to the Contractor who will ensure that
adequate tools, suitable for the work, be obtained.

6. TESTING
6.1. GENERAL
The Contractor shall supply all equipment, leads, apparatus and everything
needed to test the 11kV circuits. Any additional test as specified in relevant
ZESCO Specifications would also be applicable.
All testing shall be carried out by the Contractor and witnessed by the Project
Manager.
All tests shall be documented by the Contractor and recorded in a format as
supplied by the Project Manager.
The Contractor shall give two working days' notice to the Project Manager of
his intention to carry out tests. If for any reason the Project Manager is unable
to witness the tests, the Contractor shall proceed with testing and record the
results of the tests in the prescribed manner. The test results shall be provided
to the Project Manager. The Project Manager reserves the right to order a re-
test if he is not entirely satisfied with the results presented to him at no cost
to the Client.
The "Test Report" form shall be completed and submitted to the Project
Manager for approval.

Page 30 of 52
6.2. EARTHING INSTALLATION
The Contractor shall measure and record resistance values of all earthing
installations, which results shall be cross-referenced to the identification
numbers of the transformers as per the transformer test report.
7. FORMS

TENSIONING OF LINES
11kV LINES

From Conductor Size Tension N/kG SAG Length

Poles Pole No
No

Page 31 of 52
 II. WOOD POLE SUPPORTS

Page 32 of 52
 SPECIFICATION CONTENTS

DESCRIPTION ................................................................................................... PAGE NO

8. WOOD POLE SUPPORTS ..................................................................................... 34

9. TABLE OF WOOD POLES SIZES ....................................................................... 34
10. POLES....................................................................................................................... 35

Page 33 of 52
 8. WOOD POLE SUPPORTS
Wood Pole supports shall comply with BS 1990 “medium” or other approved
standard.
The poles shall be European redwood, pine, fir, spruce, cedar, larch or other
approved timber, straight, sound, hard grown, free from large or dead knots
or other defects, and shall have the outer and under bark completely removed.
Trees grown in Northern Europe shall have been felled not earlier than 1
November and not later than 1 March, and all trees shall have been felled
when the sap is down. Zambian, Tanzanian and South African pine may be
applied. Straight impregnated African eucalyptus poles are acceptable.
All poles, foundation bulks and other wooden members shall be properly
seasoned and they shall be submitted to preservation treatment either by
pressure creosoting in accordance with BS 144 or by organic solvent or water-
borne types of preservatives in accordance with BS 1282 or other approved
standards. As a minimum the poles shall be pressure creosoted to a minimum
net retention of 115kg creosote oil per cubic metre of wood according to BS
1990: part 1.
The poles will be inspected, and if satisfactory, branded by the Engineer at
the pole yard, before any work is done on them.
Each pole shall retain the natural butt of the tree and no timber shall be cut
from this other than that necessary to accommodate the foundation bulks and
to give the butt a flat surface.
All poles shall be notched and drilled to templates, which shall be provided
by the Contractor, for the reception of crossarms and other fittings to ensure
tight and true fitting.
Unless otherwise specified poles shall be marked at a distance of 3 metres
from the butt end to indicate classification of pole, pole length in metres, date
impregnated (last two figures of year), and species code letter as agreed.
9. TABLE OF WOOD POLES SIZES
Suitable pole sizes applicable for general use are tabled below. However,
special design situations may warrant the purchase of poles greater in length
and size than those tabled. Under these circumstances the appropriate pole
length, class and diameter will be determined by the size and type of
conductor used in the construction along with its designed ultimate tension
and line profile details. The most suitable pole will be selected from the
appropriate pole tables.

Pole Classification Top Dia in Min Dia 1.5m System useage

Length mm from the Butt
in min -max mm
Meters
7 Light 125-150 200 LV & MV
7 Medium 140-170 200 LV & MV
9 Light 125-150 180 LV & MV

Page 34 of 52
 9 Medium 150-180 220 MV & 11kV
9 Stout 190-240 275 11kV & 33kV
10 Light 125-160 185 LV & MV
10 Medium 150-180 230 MV & 11kV
10 Stout 190-245 285 11kV & 33kV
11 Light 125-160 195 LV & MV
11 Medium 150-190 240 MV.Dual.& 11kV
11 Stout 190-250 295 11kV & 33kV
12 Light 125-165 200 LV & MV
12 Medium 150-190 250 MV & 11kV
12 Stout 190-250 305 11kV & 33kV
14 Medium 160-205 260 MV & 11kV
14 Stout 195-255 335 11kV,33kV
16 Medium 170-215 305 11kV
16 Stout 200-265 365 11kV,33kV.

10. POLES
Wooden poles shall be to BS1990 /SABS 753. The poles shall have minimum
top diameters of 150mm for 9m poles and 11m poles used for overhead line
construction. Poles for transformer substations shall have a minimum length
of 11m, and minimum top diameters of 190mm.
Poles 9m long shall be subjected to a fibre stress of 55 MPa when a cantilever
loading of 5.93 kN is applied; when the cantilever loading of a 11 m pole is
7.05 kN, the stress shall be 55 MPa.
Poles for transformer substations shall be at least 11m long, with a planting
depth of at least 1.8m.
Poles for MV conductors may be 10 m, 11 m or 12 m long. MV dual
construction poles shall be 12m long and shall be buried 2m into the ground.
Preservatives of the poles shall comply with the requirements for BS144 ,
BS4072 or type A1 of SABS 590 and the impregnation shall be carried out
using the empty-cell pressure process.
Poles shall be Loop tension banded at both ends.

Page 35 of 52
 III. STAYS

Page 36 of 52
 SPECIFICATION CONTENTS

DESCRIPTION ................................................................................................... PAGE NO

11. STAYS ....................................................................................................................... 38

12. APPLIED LOADS ................................................................................................... 38
13. TRANSVERSE LOADS .......................................................................................... 38
14. VERTICAL LOADS ................................................................................................ 38
15. LONGITUDINAL TERMINAL LOADS .............................................................. 39
16. SUPPORTS ............................................................................................................... 39

Page 37 of 52
 11. STAYS
Stays shall comprise stranded galvanised steel stay wire and shall conform to
the requirements of BS 183 where applicable or other approved standard and
be tested in accordance with BS 215 in so far as it applies to steel wires. The
steel guy wires shall be performed so that they remain inert and do not move
relative to each other when the guy is cut. The individual stay wire shall
have a breaking stress not less than Grade 1000 equivalent.
The provisions of the Specification in relation to conductor drums shall also
apply to stranded stay wire. The attachment of the stays to the supports shall
be made in an approved manner.
All stays shall be equipped with stay insulators with the characteristics as
given in the Technical Schedules. The stay insulators shall be positioned so
that they are lower in elevation than any bare live metal on the support.
The angle between the stays and pole shall not be less than 30 or more than
45.
Stay rods, stay blocks and stay foundations shall be of approved dimensions
and types. Stay rods shall be fabricated in galvanised steel to the requirements
of BS 4360 where applicable, or other approved standard.
12. APPLIED LOADS
The assumed maximum simultaneous working loads on the supports, based
on the appropriate angles of deviations and span lengths and with the
particulars given in the Technical Schedules shall be as follow:
13. TRANSVERSE LOADS
(i) Normal. The normal transverse load shall be the wind pressure
stated in the Technical Schedules acting at right angles to the lines on the
whole projected area of the phase and shieldwire conductors, over the wind
span and the transverse horizontal resultant of the maximum phase and
shieldwire conductor tensions, stated in the Technical Schedules, together
with the wind pressure stated in the Technical Schedules on the Projected area
of the poles and structural steelwork.. The full wind span shall be taken
regardless of the angle of line deviation.
(ii) Wind at 45. As (i) but with wind acting at 45 to the line. For wind
at 45 the length of conductor to be considered shall be taken as the projected
length at right angles to the wind direction.
14. VERTICAL LOADS
(i) Normal. For normal load conditions the mass of the phase and
shieldwire conductors, the mass of the insulators, insulator fittings, shieldwire
conductor fittings, spacers, dampers and ancillary apparatus where
applicable. It shall be assumed that the normal loads will include the actual
total mass of the specified weight span of the phase and shieldwire conductors
stated in the Technical Schedules.
(ii) Minimum. For minimum load condition the mass of phase and
shieldwire conductors shall be considered to be zero. For conditions of uplift
a net total uplift equivalent to the mass of the length of line and earth
conductors as specified.

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 15. LONGITUDINAL TERMINAL LOADS
(i) Normal Terminal. The longitudinal components of the maximum
phase and shieldwire conductor tensions stated in the Technical Schedules.
(ii) Section. One third of the maximum working conductor tensions
tatted in the Technical Schedules.
16. SUPPORTS
Each type of support shall be so designed that no failure or permanent
distortion shall occur in any part when tested with applied forces equivalent
to the specified maximum or minimum applied loads with the overload
factors specified maximum or minimum applied loads with the overload
factors specified in the Technical Schedules. Foundations shall be designed
for the most critical compression, overturning and uplift loads multiplied by
the appropriate factors of safety specified in the Technical Schedules.
The stresses in the various parts of all supports, extensions and foundations
structures shall not exceed the figures stated in the Technical Schedules. All
foundations shall make adequate provision for horizontal shear forces in the
region of the ground line.
Steel members on which a man may stand shall be capable of withstanding
an ultimate point load of 100 kg at any point on the member.
The Contractor shall be responsible at his own cost for identifying and
classifying at an early stage of the Contract the types and nature of ground
and sub-soil encountered along the line route. Investigations shall be carried
out to confirm or adjust the parameters given for Contract purposes in the
Technical Schedules for standard foundations. Subject to the approval of the
Engineer the parameters obtained from soil test shall be classified into typical
groups and employed in the designs of all foundations.
The designs for special foundations shall consider the actual maximum
loading to which the particular structure under consideration will be subject
in service due to its position on the transmission line profile. The specified
unbalanced loading and the assumptions of temperature and wind pressure
shall otherwise apply together with the specified factor of safety.
Each class of foundation specified in the Technical Schedules shall be tested
in accordance with the requirements of the Specification. Special foundations
shall be tested under an instruction from the Engineer.
The design of pole supports and foundations shall consider the presence of
cross bracing, the requirement of which shall be determined by the Contractor
in consideration of his overall design philosophy, and the ability of pole
mounted equipment to accommodate differential settlement. The tendered
price shall be deemed to be inclusive of the cross-brace which shall be
required for the H - poles.

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 IV. OVERHEAD LINE INSULATORS

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 SPECIFICATION CONTENTS

DESCRIPTION ................................................................................................... PAGE NO

17. GENERAL ................................................................................................................ 42

18. PIN INSULATORS FOR 11 KV LINES ............................................................... 42
19. TENSION INSULATORS FOR 11 KV LINES .................................................... 42
20. INSULATORS AND FITTINGS ............................................................................ 42
21. WITHSTAND FACTOR ......................................................................................... 42
22. FITTINGS................................................................................................................. 43
23. MARKING OF INSULATORS .............................................................................. 43
24. PORCELAIN INSULATORS ................................................................................. 43
25. INSULATOR CAPS AND PINS ............................................................................. 43
26. FERROUS METAL PARTS ................................................................................... 44
27. TENSION AND STRAIN INSULATORS ............................................................. 44
28. SPINDLE .................................................................................................................. 45

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 17. GENERAL
Pin, post and reel type insulators shall be brown glazed porcelain and shall generally
comply with the requirements of the following publications:
11kV Line Post IEC 273
11 kV Tension Unit IEC 305, IEC 120, IEC 372-1
11 kV Pin BS 137/ IEC 61109
Tension insulators shall be either of strings of toughened glass or porcelain disc
insulators or comprise epoxy resin long rod type units. The design of insulators and
fittings shall be such as to avoid local corona formation and no significant radio
interference shall be exhibited. The insulator units and the complete insulator sets
shall conform to the electrical and mechanical design criteria given in these
specifications.
In addition to the above requirements a proportion of disc and pin insulators shall
be the vandal proof type of either silicon or EPDM rubber construction as specified
in the Technical Schedules.
18. PIN INSULATORS FOR 11 KV LINES
Pin type insulators for use on 11 kV shall have as a minimum the electrical
characteristics required in Technical Schedules and they shall be fitted with
galvanised mild steel spindles having a minimum failing load of 10kN. The
threaded portion of all insulator spindles shall fit a nominal 27.5 mm hole.
Spindles for pilot insulators shall have a minimum failing load of 700N. Conductor
sizes to be accommodated shall vary from 6.0 mm to 19.0 mm diameter with
preformed distribution ties.
All pin insulators shall comply with the requirements of anti-fog type insulators.
19. TENSION INSULATORS FOR 11 KV LINES
Tension insulator sets shall be either made up of strings of toughened glass disc
insulators of 254 mm diameter and fixing centres at 140 mm of 16 mm ball and
socket couplings or of epoxy resin long rod type insulators of equivalent electrical
and mechanical performance.
All disc insulators or their equivalents shall comply with the requirements of anti-
fog type units and shall have a minimum failing load of 80 kN.
The tension strings shall generally be 10-15 % longer than suspension strings. If
cap and pin insulators of the same size are used, their number should be 1-3 greater.
The testing shall be performed according to IEC 383.
20. INSULATORS AND FITTINGS
Suspension and tension insulator sets shall consist of composite type insulator units
with a minimum creepage of 25 mm/kV of the highest system voltage per phase.
21. WITHSTAND FACTOR
Complete tension insulator sets, including fittings shall have a minimum withstand
factor of 2.5 based upon the ultimate mechanical strength.

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 The ultimate mechanical strength of an insulator set shall be the load at which any
part of the insulator string fails to perform its function of providing a mechanical
support without regard to electrical failure.
Individual insulator units shall have a minimum withstand factor of 2.5 based upon
the combined electro-mechanical strength of the insulator unit. This is defined as
that load at which any part of the insulator fails to perform its function either
electrically or mechanically when voltage and mechanical stresses are applied
simultaneously.
22. FITTINGS
Ball and socket connections shall be provided with specially designed security clips
which effectively locks the connection against accidental uncoupling without
detracting from its flexibility. The security clip shall be of stainless steel.
The design shall be such as to permit easy removal for replacement of insulator
units under live line conditions without the necessity of removing the entire string
from the crossarm. All split pins for securing the attachment of fittings of insulator
sets shall be of bronze or stainless steel and shall be backed by washers. Plated split
pins shall not be used.
All bolts and nuts on insulator string fittings shall be galvanised as specified and
shall be locked in an approved manner. Split pins shall comply with the
requirements in standard IEC 372
23. MARKING OF INSULATORS
Each insulator shall have marked upon it the manufacturer’s name or trade mark,
the date of manufacture or firing indication of the guaranteed electro-mechanical
strength and other such marks as may be required to denote each batch for the
purpose of sample tests.
Unless otherwise approved the insulators submitted as a batch for a test shall bear
the same marks.
These marks shall be imprinted and not impressed. For porcelain the marks shall be
imprinted before glazing. When a batch of insulators bearing a certain identification
mark has been rejected no further insulators bearing this mark shall be submitted
and the Contractor shall satisfy the Engineer that adequate steps will be taken to
mark or segregate the insulators constituting the rejected batch in such a way that
there shall be no possibility of the insulators being re-submitted for test or supplied
for the use of the Purchaser.
24. PORCELAIN INSULATORS
All porcelain shall be sound, free from defects and thoroughly vitrified. The glaze
shall not be depended upon for insulation. The glaze shall be smooth, hard, of a
uniform shade and shall cover completely all exposed parts of the insulator.
Insulators and fittings shall be unaffected by atmospheric conditions due to weather,
proximity to the coast, fumes, ozone, acids alkalis, dust or rapid changes of air
temperature between minus 40C and plus 75 C under working conditions.
25. INSULATOR CAPS AND PINS
The caps of insulator units shall be of malleable cast iron or of forged steel having
the necessary strength to enable the complete unit to comply with this Specification.
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 The pins shall be made of forged steel or other suitable material of such quality that
the finished unit shall comply with this Specification. They shall be round and free
from cracks, surface flaws, lamination and other defects.
The design of the unit shall be such that stresses due to expansion and contraction
of any part of the insulator shall not lead to deterioration.
The porcelain shall not engage directly with hard metal. Cement used in the
construction of an insulator shall not fracture by virtue of expansion or loosen by
contraction and proper care shall be taken to locate the individual parts correctly
during cementing. The cement shall not give rise to chemical reaction with metal
fittings and its thickness shall be as uniform as possible.
26. FERROUS METAL PARTS
All ferrous metal parts except those of stainless steel shall be hot dipped galvanised
to give an average coating of zinc equivalent to 610 g per sq metre.
27. TENSION AND STRAIN INSULATORS
These shall be disk or long rod suspension insulator, reliable in service under
circumstances of varying stress and vibration. Insulator surfaces shall be smooth to
prevent adhesion of atmospheric contaminants. All metallic components shall
consist of high grade material, ensuring a safe tensile strength for insulator units.
Nominal voltage : 11kV
Type: Composite
Unit length : 300mm
Dry flash over voltage : 95kV
Wet flash over voltage : 71kV
Puncture withstand voltage 170kV
Impulse withstand voltage
Positive : 95kV
Negative : 100kV
Min failing load : 45kN
Dry arc distance : 300 mm
Minimum Creepage Distance: 340 mm

Mechanical fittings shall be of the clevis tongue type. Unless otherwise specified
long rod insulators offered shall have a clevis end fitting on the earth side, and a
tongue en fitting on the live side. Further the clevis and tongue shall be 90 twisted
relative to one another.
Pre-formed galvanised steel dead end wire-wraps with insulated thimble loops shall
be used in conjunction with 38 mm galvanised thimbles fixed to the strain insulator
tongue by means of galvanised offset shackles.

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 28. SPINDLE
Only M20 Spindles threaded from hot drawn rod, with forged collar, will be
accepted.
The collar shall be provided with two flat surfaces on the diameter. The flat surfaces
shall be suitable for a 32mm spanner to be used during installation.
The threaded portion of the spindle above the collar, and its threaded female counter
part in the insulator, shall be designed as an assembly. The two shall be made to
mate as perfectly as possible in order to avoid partial discharges which develop
when a cavity exists between the spindle and the insulating material.
All spindles to be hard stamped with manufacturer’s name and type of insulator for
which it is intended.

V. CROSS ARMS
This section covers the general requirements for the design, materials,
manufacturing, testing, and inspection for the Galvanized steel cross-arms to be
used on the overhead distribution line network.
The equipment and component supplied shall be in accordance with the latest
edition and amendments to, the following standards and specifications listed below:

Standards Descriptions

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 EN 10025 Hot-rolled products made of
non-alloy structural steels
Technical delivery conditions
ISO 898 Mechanical properties of
fasteners
ASTM Standard Specification for zinc
A123 (hot galvanized) Coating on
Products Fabricated from Rolled,
Pressed, and Forged Steel
Shapes, Plates, Bars and Strips

Steel to be used will be of grade S275 according to EN 10025. Bolts and other
connecting material will be grade 5.6 or 8.8 according to EN ISO 1461.

After the fabrication has been entirely completed, steel cross-arms shall be hot dip
galvanized to minimum of 630 g/m².

All hollow members shall be galvanized both inside and outside surfaces. No
double dip galvanising process is allowed.

Bolts, washers, & nuts shall be galvanized to full length to minimum 320 g/m².

Nuts may be re-tapped after galvanizing and then shall be suitably protected from
rust by grease. Galvanizing shall be performed in accordance with ASTM standard
A 123.

VI. 11KV OVERHEAD LINE DRAWINGS

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List of ZESCO Drawings, included in the Bid Documents for information purposes.

Description of Drawings

1. Intermediate Pole 11kV Earthed Structure

2. Section Pole 11kV Earthed Structure

3. Pin Angle 11kV Earthed Structure

4. 11kV Tee-Off Structure

Please note: All drawings in this Section are for information and bidding purposes only

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