FEDERAL UNIVERSITYOF TECHNOLOGY OWERRI

IMO STATE (PMB 1526)

A TECHNICAL REPORT
ON
STUDENT INDUSTRIAL TRAINING
(400 LEVEL)

DONE AT
TRANSMISSION COMPANY OF NIGERIA (AKANGBA SUB-REGION)
36, OFF ILLORIN STREET, ADELABU, SURULERE, LAGOS STATE,
NIGERIA.

BY
ONWUBU EMEKA PRINCEWILL
REG NO: 20161973083

SUBMITTED TO

DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING

SCHOOL OF ENGINEERING AND ENGINEERING TECHNOLOGY

IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE

AWARD OF BACHELOR OF ENGINEERING (B.ENG) DEGREE IN
ELECTRICAL AND ELECTRONIC ENGINEERING

AUGUST, 2021
 DEDICATION

I humbly dedicate this report to GOD Almighty for seeing me through my Industrial Work
Experience, and to my family for their support and encouragement. Also to My SIWES
Coordinator, Supervisor, the entire TCN crew for their full support and of course Transmission
company of Nigeria as well for an experience well shared
 ACKNOWLEDGEMENT

First and foremost, I want to acknowledge the Almighty; God that made it possible for me
to successfully complete my SIWES placement in this reputable organisation

And also thank my wonderful institution federal university of technology, owerri {FUTO}

me this great opportunity. I will ever remain grateful. My parent not left out for their
continual support throughout the training period.
 ABSTRACT
This is a report that contains information pertaining my SIWES period at TCN. It contains
information about the organizations, the activities I participated in, the challenges I
encountered, and observations and contribution made. Some of the activities I participated
Are annual maintenance of transformers and different substations under TCN Akangba and
protection and control of major power equipments
 TABLE OF CONTENTS
TITLE PAGE …………………………………………………………….......i

DEDICATION………………………………………………………………………………....ii

ACKNOWLEDGEMENT……………………………………………………………………...iii

ABSTRACT……………………………………………………………………………………...iv

TABLE OF CONTENTS………………………………………………………………….….v

TABLE OF FIGURES ………………………………………………………………….…….vi

CHAPTER 1: ABOUT SIWES.............................…………………………………………1

1.1 Definition and history of SIWES.....................................................................................1

1.2 ITF……………………………………………………………………………………….2

1.3 Aims and objectives .........................................................................................................4

1.4 Bodies involved in management of siwes........................................................................4

CHAPTER 2:COMPANY PROFILE…………………………………………………5

1.1 Transmission station at akangba work centre.....................................................5

1.2 Brief history of transmission company of Nigeria..................................................5
1.3 Transmission of electricity…………………………………………………………6
1.4 Organogram of TCN……………………………………………………………….7

CHAPTER 3: THEORETICAL FRAMEWORK.......................................................8

3.1 TRANSFORMERS……………………………………………………………….8
3.1.1 transformer components and their function................................................9
3.1.2 instrument transformer.................................................................................9
3.2 Electrical protection…………………………………………………………11
3.3 Test for transformers……………………………………………………………..19
3.4 Lines maintenance department…………………………………………………….30
3.5 Battery bank maintenance……………………………………………………….34

CHAPTER 4: INDEPENDENT SYSTEM OPERATION (ISO)..............................35

4.1 Some equipments associated with this department...............................................35

4.2 Experience gained in the department........................................................................37
4.2.1 She scada system......................................................................................................37
4.2.2 Daily inspection of equipments.................................................................................38

CHAPTER 5: CHALLENGES OF SIWES……………………………………………39

5.1 Recommendations ……………………………………………………………….39

5.2 Conclusions…………………………………………………………………………39

REFERENCES……………………………………………………………………………40
 TABLE OF FIGURES

L1ST OF TABLES
Tab 1.0 open circuit test
Tab 2.0 core balance tests
Tab 3.0 short circuit test
LIST OF FIGURES
Figure 1. power transformer
Figure 2. capacitor voltage transformer
Figure 3. current transformer
Figure 4. protective relay
Figure 5. circuit breaker
Figure 6 over current and earth fault protection circuit diagrams
Figure 7 buchholz relay diagram
Figure 8 restricted earth fault protection
Figure 9 winding resistance diagram
Figure 10 open circuit test
Figure 11 short circuit test
Figure 12 insulation resistance test
Figure 13 physical structure of a tower
Figure 14 ijora 132/33kv tower
Figure 15 suspension tower
Figure 16 angle tower
Figure 17 tension tower
Figure 18 110vdc battery bank
Figure 19 frequency counter
Figure 20 computer
Figure 21 control/protection panel
Figure 22 the scada system
 CHAPTER ONE
ABOUT SIWES

1.1 DEFINITION AND HISTORY OF SIWES

Student Industrial Work Experience Scheme(SIWES) was established by ITF in 1973 to solve

the problem of lack of adequate practical skills preparatory for employment in industries by
Nigerian graduates of tertiary institutions.

The Scheme exposes students to industry based skills necessary for a smooth transition from the
classroom to the world of work. It affords students of tertiary institutions the opportunity of
being familiarized and exposed to the needed experience in handling machinery and equipment
which are usually not available in the educational institutions.

Participation in SIWES has become a necessary pre-condition for the award of Diploma and
Degree certificates in specific disciplines in most institutions of higher learning in the country, in
accordance with the education policy of government.

Operators - The ITF, the coordinating agencies (NUC, NCCE, NBTE), employers of labour and
the institutions. 
Funding - The Federal Government of Nigeria
Beneficiaries - Undergraduate students of the following: Agriculture, Engineering, Technology,
Environmental, Science, Education, Medical Science and Pure and Applied Sciences.
Duration - Four months for Polytechnics and Colleges of Education, and Six months for the
Universities.

Highlight Number of Participating Institutions:

Universities 59
Polytechnics 85
The number of students that participated in SIWES from
Colleges of Education 62
Universities, Polytechnics and Colleges of Education at the end of
TOTAL 206
the 2007 fiscal year was 194, 890
1.2 INDUSTRIAL TRAINING FUND(ITF) was stablished in 1971, the Industrial Training
Fund has operated consistently and painstakingly within the context of its enabling laws, i.e.
Decree 47 of 1971. The objective for which the Fund was established has been pursued
vigorously and efficaciously. In the three decades of its existence, the ITF has not only raised
training consciousness in the economy, but has also helped in generating a corps of skilled
indigenous manpower which has been manning and managing various sectors of the national
economy. Over the years, pursuant to its statutory responsibility, the ITF has expanded its
structures, developed training programmes, reviewed its strategies, operations and services in
order to meet the expanding, and changing demands for skilled manpower in the economy.
Beginning as a Parastatal "B" in 1971, headed by a Director, the ITF became a Parastatal "A" in
1981, with a Director-General as the Chief Executive under the aegis of the Ministry of
Industry. The Fund has a 13-member Governing Council and operates with 6 Departments and
3 Units at the Headquarters, 27 Area Offices, 2 Skills Training Centres, and a Centre for
Industrial Training Excellence.As part of its responsibilities, the ITF provides Direct Training,
Vocational and Apprentice Training, Research and Consultancy Service, Reimbursement of up
to 60% Levy paid by employers of labour registered with it, and administers the Students
Industrial Work Experience Scheme (SIWES). It also provides human resource development
information and training technology service to industry and commerce to enhance their
manpower capacity and in-house training delivery effort.The main thrust of ITF programmes
and services is to stimulate human performance, improve productivity, and induce value-added
production in industry and commerce. Through its SIWES and Vocational and Apprentice
Training Programmes, the Fund also builds capacity for graduates and youth self-employment,
in the context of Small Scale Industrialisation, in the economy
1.3 AIMS AND OBJECTVES OF SIWES
1. Provide avenues for student to acquire industrial skills that may not be experienced
during their course of study.
2. Expose student to work methods and techniques in handling equipment and machineries
that may not be available in the university.
3. Prepare student for industrial work situation they are likely to meet after graduation.
4. Provide student with the opportunities to apply their educational knowledge in real work
situation, thereby bringing the gaps between theories for practice.
5. To make the transition from the schooling to world of work easier through enhancing
student contact for later job placement

1.4 BODIES INVOLVED IN THE MANAGEMENT OF SIWES PROGRAMME

 FEDERAL GOVERNMENT
 INDUSTRIAL TRAINING FUND (SIWES DIVISION)
 THE SUPERVISING/REGULATORY AGENCIES NUC (National Universities
Commission) NBTE (National Board For Technical Education NCCE National
Commission For College Of Education)
 CHAPTER 2

COMPANY PROFILE

2.1 TRANSMISSION STATION AT AKANGBA WORK CENTRE

Akangba work centre was commissioned in 1968, and is located at 38 Ilorin Street off Adelabu
road Surulere Lagos.

Akangba work centre is a 330/132/33Kv key switching station. As power comes in through a
double circuit of 330Kv from Ikeja –west which are stepped down to 132Kv by the 2 by
150MVA and 4 by 90 MVA transformers in the 330Kv switchyard.

In the 132Kv switchyard two outgoing lines each goes to Ijora, Isolo, Ilupeju, Itire and Ojo
transmission stations which are 132/33Kv stations. At the upstream, we have 4 by 60MVA
which is 132/33Kv transformer winding and 2 by 45MVA which also is a 132/33Kv transformer.

2.2 BREIF HISTORY OF TRANSMISSION COMPANY OF NIGERIA (T.C.N)

As part of the evolution in the power industry in Nigeria, the Federal government by decree No
24 0f 1972 created the National Electric Power Authority (NEPA). This was consequent upon
the merger of the electricity corporation of Nigeria (ECN) and the Niger dam authority (NDA).
In September 1990, the partial commercialization came into being with the appointment of a
managing director/chief executive to super intend over the corporation. Also the authority was
divided into four autonomous divisions namely; Generation and Transmission; Distribution and
sales; engineering; finance and Administration each division was headed by an executive
director.

The Federal Government of Nigeria (FGN) took further steps towards the restructuring of the
Nigeria power sector to establish an electricity supply that is efficient, reliable and cost effective
throughout the country that will attract private investment. Subsequently, another power reform
act was enacted in 2005, transferring the public monopoly of NEPA to Power Holding Company
of Nigeria (PHCN) which was unbundled into 18 business units (BU) viz; (11) distribution
companies; six (6) generation companies and one (1) transmission company.
The Transmission Company of Nigeria (TCN) is one of the successors of the unbundled PHCN
and is currently an asset held under custodianship of the Federal ministry of power. It will
initially remain public owned TCN has the responsibility of management of operation,
maintenance and expansion of 132Kv and 330Kv transmission systems. The bureau of public
enterprise (BPE) recently appointed a management contractor, Hydro International (MHI) for
TCN which took over the functions of transmission service provider, system operator and market
operator to undertake the overall management of TCN

2.3 TRANSMISSION OF ELECTRICITY

The process by which electrical energy is being transported from generating station to load
centre and injection sub stations through power lines and cables is known as electrical energy
transmission. In Nigeria, electricity generated from remote generating station is usually
transmitted at high voltage by overhead lines over a considerable distance to primary power
transforming systems and switching substations (330/132/33/11Kv) switchyards located at
reasonable and suitable points like Akangba work centre that has 330/132/33Kv switchyards.
O
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2.4 ORGANOGRAM OF TCN

Fig 3.5 ORGANOGRAM

AGM: Assistant General Manager

PM: Principal Manager

S/O: System operations

S.M: Senior Manager

PC&M: Protection control and metering

F/A: Finance/Accounts

H/R: Human Resources

OT TCN AKANGBA
 CHAPTER THREE

THEORETICAL FRAMEWORK

3.1 TRANSFORMER

A transformer is a static machine used from changing power from one circuit to another without
changing the frequency. A transformer efficiently converts electric power from one voltage level
to another. It consists of two coils coupled together magnetically for energy transfer.

Fig1. A power transformer

In an ideal transformer, the voltage on the input and output side are related by the transformer
turns ratio which is;

V1 = N1V2/N2
Where N1 and N2 are the numbers of turns in the primary and secondary side respectively and V 1
and V2 are the voltages on the primary and secondary windings.

In real transformers, not all flux couples between the windings so the voltage relationship
is thus;

V1 =(N1V2/N2) - XLI1

Where XL is the leakage current in ohms and I L is the current out of winding one(i.e. primary
winding).

3.1.1 TRANSFORMER COMPONENTS AND THEIR FUNCTION

1. The transformer coil or winding: The transformer is made up of primary and secondary
windings. The primary winding is connected to the supply and its function is to circulate
a current that will magnetize the core. The secondary windings supplies the load, its
function is to have the secondary voltage induced into it.
2. The transformer oil: It is obtained from the fractional distillation of crude petroleum.
That is why it is called mineral insulating oil. It serves the major purpose of liquid
insulation in electric power transformer for dissipation of heat i.e. acting as a coolant, in
preservation of the core and winding as these are fully immersed inside the transformer
oil and furthermore, it prevents direct contact with atmospheric oxygen in order to
prevent oxidation of the cellulose made paper insulation of windings.

3.1.2 INSTRUMENT TRANSFORMERS

These are high accuracy class electrical device used to isolate or transform voltage or
current levels. The most common usage of instrument transformers is to operate
instruments or metering devices from high voltage or high current circuits safely isolating
secondary control circuitry from high voltage or current. Instrument transformers include;
1. Capacitor voltage transformer VT (potential transformer); it is a type of instrument
transformer used for stepping down high voltage to a safe value or level which can be
fed and easily handled by metering and control devices since commercially available
relays and metres used for protection and metering are designed in low voltage.

Fig 2 A capacitor voltage transformer

2. Current transformer CT: This is a type of instrument transformer used for

measurement of alternating currents. When current in a circuit is too high to apply
directly to metering instruments, a CT produces a reduced current accurately proportional
to the current in the circuit which can be applied to measuring instruments. The CT is
commonly used for protection and metering.
 Fig 3 A current transformer

3.2 Electrical protection: PROTECTION CONTROL AND METERING

DEPARTMENT

Introduction

Protection of Transformer is very important to ensure a reliable power system. Power

transformer have a more reliable protection system compare to Small distribution transformers
due to the cost, size, numbers of feeders and its power capability. Distribution transformer can
be protected satisfactorily, from both technical and economic considerations,
and transformer accessory faults, On -load tap changer faults, Abnormal operation conditions,
Sustained or unclear external faults

Electrical Faults are faults which cause immediate serious damage such as phase to earth or
phase to phase faults, short circuits between turns of High voltage and Low voltage windings,
etc. The protection of these faults comprises of fuse protection, circuit breaker, differential
protection, over current protection, Buchholz protection, and restricted earth fault (REF)
protection, over fluxing relays etc.

1. PROTECTIVE RELAY
 A relay is an electrical device which responds to its input information in a prescribed way
and its contact operation causes a sudden change in associated control circuits. A
protective relay simply detects faults and triggers the circuit to prevent the fault from
damaging the transformer. Relay or relaying protection is used to prevent or minimize
damage to power system equipment and maintain continuous supply of electricity at
barest minimum cost.

Fff
Fig 4 protective relay

2. FUSES PROTECTION
Fuses commonly protect small distribution transformers from over current and are used typically
on transformers up to ratings of 1 MVA at distribution voltages. The fuse must have a rating well
above the maximum transformer load current in order to withstand the short duration overloads
that may occur. Also, the fuses must withstand the magnetizing inrush currents drawn when
power transformers are energized. Fuses are used in electric power systems, devices or
equipment for the protection of circuits. It is defined as an over-current device with a circuit
opening component heated and destroyed by `excessive' current passing through it. The fuse
should be able to carry normal current continuously, subject to its nominal rating without
deterioration and when subjected to excessive current, it should open the circuit reliably and
quickly.

3. CIRCUIT BREAKER
 During the operation of power system, it is often desirable and necessary to switch on and off
various circuits under both normal and abnormal conditions. With advancement of power
system, the lines and other equipment’s operate at very high voltages and carry very large
currents. The arrangement of switches along with fuses cannot serve the desired function of
switch gear in such high capacity circuits hence; the use of circuit breakers comes to play. A
circuit breaker is both a switching and current interrupting device used either to make or
break supply in microseconds. A circuit breaker can make or break circuit either manually or
automatically under the following conditions,no load, full load, and short circuit conditions.
Hence making it a very useful equipment for switching and protection of various part of
power system.

Fig 5 A circuit breaker

4. Over current and Earth Fault protection.

The philosophy of transformer over current protection is to limit the fault current below the
transformer through fault withstand capability. Over current/ Earth fault is commonly used for
protection from phase to phase and phase and ground faults basically for external fault. It is used
as primary protection where differential protection is not used and also as backup protection if
differential protection is used. This protection is applied against external short circuits and
excessive overloads and the relays used are time over current relays of the inverse type, of the
IDMT type or of the definite time.
Figure 6: over current and Earth fault protection circuit diagram

5. Buchholz Protection.
Whenever a fault in transformer develops slowly, for an incident fault (such as sparking, small
arcing, loose connections in conducting path etc.) and violently heavy faults, heat is produced
locally, which begins to decompose the transformer oil and thus to produce inflammable gas and
oil flow. This phenomenon has been used in the gas protection relay or popularly known as
Buchholz relay. This relay is applicable only to the conservator type transformer in which the
transformer tank is completely filled with oil, and a pipe connects the transformer tank to an
auxiliary tank or “Conservator" which acts as an expansion chamber. As the gas accumulates for
a minor fault, the oil level falls and with it a float which operates a mercury switch sounding an
alarm. When a more serious fault occurs within the transformer during which intense heating
takes place, an intense liberation of gases results. These gases rush towards the conservator and
create a rise in pressure in the transformer tank due to which the oil is forced through the
connecting pipe to the conservator. The oil flow develops a force on the lower float causing its
contacts to complete the trip circuit of the transformer breaker. Operation of the upper float
indicates an incipient fault and that of the lower float a serious fault.

Figure 7: Buchholz relay diagram

Precautions in Buchholz relay operation: The Buchholz relay may become operative not only
during faults within the transformer. For instance, when oil is added to a transformer, air may get
in together with oil, accumulate under the relay cover and thus cause a false operation of the gas
relay. For this reason, when the 'Gas' alarm signal is energized the operators must take a sample
of the gas from the relay, for which purpose a special clock is provided. Gases due to faults
always have colour and an odour and they are inflammable, also the gas can be remove by just
bleeding method using the bleeding nozzle installed in the transformer.

The lower float may also falsely operate due to the oil velocity in the connection pipe for internal
faults. This can occur in the event of an external short circuit when over currents flowing through
the windings, over-heat the copper and the oil, and cause the oil to expand. If mal-operation of
Buchholz relay due to overloads or external short circuits is experienced it may be necessary,
that the lower float is adjusted for operation for still higher velocities. In installing these relay,
the following requirements should be fulfilled.

a) The conductor connection on the contacts to the terminals on the cover must have paper
insulation, as rubber insulation may be damaged by the oil.
b) The floats must be tested for air tightness by for example, submerging them in hot oil to
create a surplus pressure in them.

c) The relay cover and the connection pipe should have a slope of 1.5 to 3 percent and not
have any protruding surface to ensure unrestricted passage of the gases into the conservator.
 Restricted Earth Fault Protection (REF)

Figure 8: Restricted Earth fault Protection (REF)

This is a unit protection system used as a form of protection provided to prevent the earth fault
relay EFR acting on spurious external faults and operates only when there is an internal earth
fault within the transformer and thus fast operating timer can be achieved.

1. An external fault on the star side will result in current flowing in the line CT of the affected
phase and a balancing current in the neutral CT and current in the relay is zero and hence relay is
stable. During an internal fault, the line current on the line CT gets reversed and hence relay
setting is instantaneous in operation.

2. The arrangement of residually connected CTs on the delta side of a transformer is only
sensitive to earth faults on the delta side because zero sequence currents are blocked by the delta
winding.

6. Differential Protection
This is a unit protection scheme for all power transformers rated at 5MVA and above. A
Differential relay compares the currents on both sides of the transformer. As long as there is no
fault within the zone of protection, the current circulates between the two CTs and no current
flows through the differential element. But for internal faults the sum of the CTs secondary
currents will flow through the differential relay making it to operate. Transformer differential
relays are subject to several factors, not ordinarily present for generators that can cause mal-
operation these factors are

a) Different voltage levels, including taps, which result in different primary currents in the
connecting circuits.
b) Possible mismatch of ratios among different current transformers. For units with ratio
changing taps, mismatch can also occur on the taps. Current transformer
Performance is different particularly at high currents.

c) A 30o phase angle shift introduced by Delta-star or Star-Delta connections.

d) Magnetizing inrush currents which the differential relay sees as internal faults.
All the above factors can be accommodated by the use of percentage differential relay and
current transformer design along with the use of auxiliary C. Ts, proper application and
connections.

8.Surge Diverters (lightning Arresters)

This is another form of protection in both power and distribution transformers for the protection
and lightning and over voltage that could occur in the system.

Lighting arrester are always placed at the incoming source of supply, some few meters before the
transformer, for each of the phases (red, yellow and blue phase) they are classified based on

1. Rated voltage

2. Rated current

3. Rated frequency.

9. Rod gap/ spark gap

This is a backup protection to lightning arresters. It is mounted on the transformer bushing.

Other Protective devices employed in Transformer are

10. Pressure Relief Value (PRV)

11. Winding Temperature

12. Oil Temperature

13. OLTC Buchholz

3.3 TESTS FOR TRANSFORMERS

High-voltage transformers are some of the most important (and expensive) pieces of equipment
required for operating a power system. The purchase, preparation, assembly, operation and
maintenance of transformers represent a large expense to the power system. When transformers
are received from the factory or reallocated from another location it is necessary to verify that
each transformer is dry, no damage has occurred during shipping, internal connections have not
been loosened, the transformer’s ratio, polarity, and impedance agree with its nameplate, its
major insulation structure is intact, wiring insulation has not been bridged, and the transformer is
ready for service. When transformers stay in service or trip due to fault it is also necessary to
check the condition of the transformer.

Tests perform on a power transformer

There are several tests that can be done on the transformer; however, a few common ones are
listed and discussed here.

1. Winding resistance test

2. Polarity test

3. Open circuit test

4. Short circuit test

5. Core balance test

6. oil test
 7. Insulation resistance test

8. Capacitance/ Tan delta test

9. Physical test

These test are classified into

1. Routine test

2. Field/Commissioning test

Routine test

These tests are conducted to confirm the operational performance of the transformer

1. Measuring the winding resistance

2. Short circuit test in all taps

3. Open circuit in all taps

4. Insulation resistance

5. Separate source voltage withstand test

Field Test and Commissioning test

These tests are conducted at the time of commissioning on a completely assembled transformer
after necessary drying out of the winding core and filling the oil.

 Measurement of insulation resistance and polarity index

 Ratio test on all the taps

 Short circuit test/ load losses on all taps

 Oil test
  Operation of tap changer manually and electrically on local and remote

 Operation of cooling fans/pump and motors

 Measurement of earth resistance of transformer ground namely neutral and body.

 Operation of buchholz relay for alarm and tripping.

1. Winding Resistance Test

This is done to determine the pure ohmic resistance from each phase windings and terminal
connection both in high and low voltage by applying a smallDC voltage to the winding and
measuring the current through the same. The ratio givesthe winding resistance, more commonly
feasible with high voltage windings. The transformer winding resistances can be measured either
by current-voltage method or bridge method. If digital measuring instruments are used, the
measurement accuracy will be higher. For low voltagewindings, a resistance-bridge method can
be used. From the D.C resistance, one can get theA.C resistance by applying skin effect
corrections.

Figure 9 : Winding Resistance by current – voltage Method

 2. Open circuit Test

This is also called Ratio test or no load loss test. We also get the magnetizing or excitation
current when this test is performed. The no load loss of a transformer isgrouped into three; iron
loss at the core of the transformer, dielectric loss at the insulating material and the copper loss
due to no load current. The last two are of small value and can be ignored, so only the iron losses
are considered in determining the no load losses.
Procedures of performing Ratio test/no load test/magnetizing current test/exciting current test
 Isolate the transformer from service
 Remove the high voltage and low voltage jump and disconnect the neutral from
earth/ground
 The secondary side (Low voltage) of the transformer is kept open circuited and voltage
(415v) is feed into the primary side (high voltage) to energise the transformer.
 The primary voltage V1 is measured and recorded in the three phases and in all the taps
using the voltmeter
 The secondary voltage V2 is measured and recorded in the three phases and in all the taps
using voltmeter.
 The primary current (Magnetizing or exciting current) is measured and recorded in the
three phases and in the entire taps using ammeter.

 Ratio=V1/V2 (each phase) Expected variation should be within 0.5%

fig 10 open circuit test

 3. Short circuit test
This is also called the load test and shows the general performance of the transformer.The test is
conducted on the high voltage (primary) side of the transformer where the low voltage
(secondary) side is short circuited. The supply voltage required to circulate rated current through
the transformer is usually very small and is of the order of a few percent of the nominal voltage
and this 5% voltage is applied across primary. The core losses are very small because applied
voltage is only a few percentage of the nominal voltage and hence can be neglected. Thus only
the full load copper loss is considered.

Procedures of performing short circuit test

 Isolate the power transformer from service.

 Remove the primary (High voltage) and secondary (low voltage) jumps and
disconnect neutral from earth/ground.
 Short low voltage phases
 Feed 415 supply voltage into the primary side (high voltage) to energize the
transformer supply.
 Measure current in neutral, primary line voltage, secondary line voltage primary
current, secondary current

If neutral current is near to zero transformer windings are operational.

Fig 11 short circuit test

 4. Core balancing Test

This is also called a magnetic balance test, it is conducted on Transformers to identify inter turn
faults and magnetic imbalance, usually done on the star side of a transformer.

Transformer failure can be attributed to the unbalanced distribution of flux in transformer core
due to interterm short circuits of windings, physical displacement of windings on the core due to
electromagnetic forces while in operation, transportation, etc.

Procedures of performing core Balance Test

 Keep the tap changer of the transformer in normal position

 Disconnect the transformer neutral from ground
 Apply single phase 220v AC supply across one of the winding terminals and neutral
terminal
 Measure the voltage in two other high voltage terminal in respect of the neutral terminal
 Repeat the test in each of the three phases

A single phase supply 240V is applied across a phase and a neutral, say Red (R), Yellow(Y) or
Blue (B) and neutral (N). The voltage is then measured between R-Y, R-B and Y-B (Primary) r-
y, r-b, y-b (Secondary).  The sum of these two voltages should give the voltage of the other. 
That is, R-B + Y-B will be equal to R-Y (Primary) and also r-b + y-b will be equal to r-y
(secondary).

The Magnetic balance test is only an indicative test for the transformer. Its results are not
absolute.  It needs to be used in conjunction with other tests.

5. Oil Test

The mineral oil in transformers is used not only as an insulating medium but also for cooling of
the windings and core. The test performed in a transformer are to determine the dissolve gas
analysis; acidity level, water content, sludge value, breakdown voltage, etc. The equipment used
to perform this test are Transport X, Megger oil tester.
 6. Insulation Resistance Test

This is also called Megger test; it measures the quality of insulation within the transformer. Some
variations will be obtained depending on the moisture, cleanliness and the temperature of the
insulation. It is recommended that tank and core should always be grounded when this test is
performed. Resistance is then measured between each winding and all other windings and
ground.

Procedures for performing Insulation Resistance

 Disconnect all the line and neutral terminals of the transformer

 Megger leads to be connected to Low voltage and High voltage bushing studs to measure
insulation resistance value in the Low voltage and High voltage windings

 Megger leads to be connected to High voltage bushing studs and transformer tank earth
point to measure insulation Resistance value in between the High voltage winding and
earth.

 Megger leads to be connected to low voltage bushing studs and transformer tank earth
point to measure insulationResistance Value in between the low voltage winding and
earth

fig 12 insulation resistance test

A TYPICAL EXAMPLE OF THE READINGS GOTTEN FOR THE VARIOUS
TRANSFORMER TESTS

OPEN CIRCUIT TEST

Tap Injected voltage Measured Magnetizing current
(primary) voltage (Imag)
positio
(secondary)
n

s/n R-Y Y-B B-R r-y y-b b-r R Y B N

1 359.2 360.8 356.9 82.5 82.2 81.8 43.8 43.5 40.7 127.8

2 361.0 360.8 357.1 85.3 82.4 82.9 45.2 45.1 42.2 125.8

3 360.7 360.7 357.4 85.0 84.1 82.7 44.6 44.4 41.8 132.9

4 361.0 355.7 357.7 83.0 85.2 82.0 46.5 46.2 43.4 128.5

5 359.7 361.6 356.9 78.5 82.9 84.7 48.0 48.0 45.3 141.9

6 360.3 360.2 356.7 86.7 87.1 85.5 50.1 49.7 46.8 147.7

7 360.0 359.7 356.2 89.4 88.2 87.4 51.1 50.5 47.7 150.8

8 358.5 359.2 352.0 89.4 88.9 87.6 51.6 51.5 48.5 153.7

9 359.4 360.0 355.3 89.9 89.2 90.0 53.2 53.6 50.5 158.8

10 358.9 359.8 355.7 91.6 90.5 89.8 55.3 55.0 51.5 157.9

11 358.3 358.4 354.6 93.3 91.2 91.6 45.6 42.6 41.9 134.7

12 358.1 357.8 359.2 96.5 92.6 92.0 46.4 46.2 42.9 135.8

13 357.9 359.1 358.4 94.3 94.4 94.4 47.9 47.2 43.6 145.8

14 358.3 359.0 358.3 97.2 96.5 94.3 51.0 49.9 46.9 149.8

15 358.4 359.0 359.2 95.8 98.4 97.3 51.5 51.9 49.5 146.3

16 358.0 358.7 359.4 99.9 99.7 98.7 65.6 63.0 61.1 167.4

17 367.9 364.0 364.1 103 102 100.2 66.0 66.0 61.8 178.7
Tap Injected voltage Measured Measured
positio current(primary current(secondary)
n )

S/N R-Y Y-B B-R R Y B R Y B CORE

BALANCING
1 363.0 368.0 359. 5.2 5.2 5.0 25.1 24.4 24.4
TEST
0
TAP 1
2 366.0 368.4 362. 5.4 5.3 5.1 25.5 24.8 24.8
R-N 211.5 Y-N 2213.3 B-N 209.5

3R-Y 390.4
363.0 R-Y 365.0 5.6R-Y 5.6 244.5
364.0 362. 5.2 26.0 25.2 25.2
6
Y-B 201.1 Y-B 264.0 Y-B 433
4 367.2 369.0 362. 5.8 5.7 5.4 26.5 25.7 25.6
B-R 262.0 B-R 100.5 B-R 192.1
8
r-y 74.5 r-y 82.8 r-y 89.5
5 366.4 366.0 363. 5.9 5.9 5.5 26.8 26.1 26.0
y-b 34.9 y-b 321.4 y-b 82.2

6b-r 83.4
367.1 b-r 60.8
368.0 362. 6.1b-r 6.1 8.35.8 27.2 26.6 26.5
4
Image 2.0mA Imag 1.1mA Image 1.7Ma
7 367.1 e366.0 384. 6.3 6.2 6.0 27.9 27.1 27.0
0

8 362.1 364.0 363. 6.5 6.5 6.3 27.5 27.4 27.4

3

9 366.7 367.3 362. 6.7 6.7 6.5 28.8 28.0 28.0

8

10 365.6 366.7 358. 6.9 6.9 6.6 29.2 28.5 28.4 SHORT

0 CIRCUIT TEST

11 360.7 363.0 357. 7.1 7.1 6.9 29.8 28.9 28.9

0

12 366.7 365.0 362. 7.4 7.4 7.1 30.2 29.4 29.3

0

13 366.5 367.1 361. 7.5 7.6 7.4 30.4 29.9 29.6

8

14 366.2 367.0 362. 7.8 7.9 7.6 31.2 30.4 30.3

3.4 LINES MAINTENANCE DEPARTMENT

This department basically works on everything concerning transmission lines and its
maintenance and also setting up new towers in various locations. The ones in which I
participated in are;
1.Tower maintenance: Tower maintenance mainly consists of clearing unwanted bushes around
the tower and checking for any burnt or damaged glass disc conductors, and any form of
detached conductors and these damaged conductors are changed to silicon composite conductors
on all the lines of all phases. The physical structure of a tower as shown in fig 2.2and 2.3 an
example of a tower and a tower at Ijora 132/33kv transmissionstation.

Fig 13and 14

SILICON COMPOSITE CONDUCTORS:

A silicon composite insulator used in transmission lines

EQUIPMENTS USED IN LINES AND TOWER MAINTENANCE

1. Hook ladder
2. G-shackle
3. tirfor
4. grounding stick and lead
5. silicon composite/glass disc
6. hammer
7. hand line
8. safety belts
9. binding wire
10. pull lift
11. tool box

a b c
 d e

a. Grounding stick, b. hook ladder. C. tirfor d. glass disc e. pull lift

me using a grounding stick to ground a line at ojo transmission

station 132/33kv
TRANSMISSION TOWERS

They consist of different types used in carrying power transmission lines for a 330kv
transmission tower they are spaced 400km apart, for a 132kv tower they are spaced 300km apart

1. Suspension towers: a structure carrying conductor

fig 15 suspension tower

2. Angle towers: these are used for diversions

Fig 16 angle tower

 3. Tension towers: these are parallel to the level of the conductors

Fig 17 tension tower

3.5 BATTERY BANK MAINTENANCE

Akangba work centre and other stations under it such as Itire, Ilupeju, Isolo, Ojo etc. have a
110vdc battery bank in the station this battery bank serves a very important purpose because;

 All electrical protection equipment’s such as relays, frequency meters, etc. work with
exactly 110vdc and not more than 5A
 When there is system collapse or the station goes off these protection devices will be able
to keep working and not go off and it enables the system operator to detect any fault from
the alarms

If not done the system operator cannot detect if any transformer has tripped or a circuit
breaker or CT has an issue and it could lead to hazards in a station or the station around it.it is
said to be the life support of the station

Fig 18A 110vdc battery bank at ilupeju 132/33kv transmission station

Each cell must not be less than 2.2v and there are 55 cells in each battery bank

fig 4.2 me topping the electrolyte level of the

battery cell
 CHAPTER FOUR

INDEPENDENT SYSTEM OPERATION (ISO)

The period spent in this department was 4 weeks. The broad responsibilities of this department
can be simply categorized into three functions, which are: Control, Monitoring and
Maintenance.

 Control: The elements of the switchyard can be controlled locally, manually or remotely.
This department is responsible for the isolationof elements in switchyard when work is to
be carried out in the switchyard. They are the ones that grant permission for work to be
carried out in the switchyard and guarantee that it is safe to work on an element after the
element has been isolated
 Monitoring: This department monitors the values of the energy consumed and help
maintain the stability of the grid by load shedding, which involves cutting down some of
the loads consuming more energy than the generating unit can handle in order to avoid
system collapse. This monitoring aspect of this department is achieved with the help of
SCADA (Supervisory Control and Data Acquisition).
 Maintenance: This is another very important task performed by this department. They
perform a daily routine check on the condition equipment in the switchyard. They check
and take note of pressure gauge of the circuit breakers, the surge arrester gauge, the
gauge of the VTs and CTs, the condition of the isolators and then the batteries in the
battery bank. They are the ones that report any anomaly in any equipment in the
switchyard to the department responsible for taking action. The relays in the control room
help a lot in the achievement of this goal, as they tend to alert the personnel on duty of
any fault in any equipment in the switchyard.

4.1 SOME EQUIPMENT ASSOCIATED WITH THIS DEPARTMENT

The major equipment employed by this department includes:

a. Frequency monitor: This equipment helps to read the frequency of the system
instantaneously. It displays the revolution per second of the motors in the generation
unit. This information helps in maintaining balance between energy generated and
energy consumed
b. Control panels: These are integrated circuits that contain the controls of the
protective elements of different lines and different transformers in the switchyard.
When these elements are operated from the control panel, they are said to be
remotely operated, when the controls on the panel are set to SCADA then these
elements can be operated remotely from a computer system. These protective
 elements include the circuit breakers and isolators. The control panels also contain
the controls of the capacitor banks and bus couplers.
c. Protection panel: These are integrated circuits that consist of different relays
responsible for sending trip signals when there is any fault in a line, transformer,
circuit breaker or any other element in the switchyard. They are essential for
monitoring and maintenance.
d. Computer systems: These are normal personal computers with normal windows
operating system used for data collection and cataloguing of data acquired from the
SCADA. They are also used for operating the elements in the switchyard remotely
when the control panel has been set to SCADA.

Fig 19 fig 20

.fig 21

Some ISO equipment

4.2 EXPERIENCE GAINED FROM THIS DEPARTMENT

1. The SCADA system

2. Daily inspection of equipment

4.2.1 THE SCADA SYSTEM

Supervisory Control and Data Acquisition or simply SCADA is one of the solutions available for
data acquisition, monitor and control systems covering large geographical areas. In the control
room, there are two computer systems set aside to perform this function. These two computers
contain the schematic representation of the equipment in the switchyard and display the electrical
quantities of the equipment in real time. The functions of the SCADA can be divided into three:

 Data acquisition: Data acquisition refers to acquiring or collecting data. In the control
room, one of the SCADA systems is set to capture the readings of the electrical
quantities of equipment in the switchyard every hour. This helps in keeping the record of
the power consumed by the station every hour and helps in the computation and
processing of the charge on the power transmitted per hour.
 Supervision: The SCADA system helps in monitoring the conditions and status of the
equipment in the switchyard. Whenever there is a fault on any equipment, the relay
responsible for identifying the fault sends an alarm to the SCADA system, this
information now helps in determining the best course of action
 Control: The SCADA system can also be used for controlling the equipment in the
switchyard remotely; this is achieved by setting the equipment in the switchyard to
remote, and then coming to the control panel and setting the equipment to SCADA, with
this setup the SCADA can be used to operate the equipment.
 fig 22

The SCADA system

4.2.2 DAILY INSPECTION OF EQUIPMENT

The system operation personnel carryout their duties in the control room for 24 hours a day and 7
days in a week, as such, the work in shifts. One of the first things any personnel does after taking
over a shift is to physically go into the switchyard and inspect the equipment to ensure that they
are in good condition; same thing is done for the equipment in the control room before the
personnel can continue their daily duties. Some of the inspections carried out include:

1. Taking note of the SF6 gas circuit breaker gauge pressure

2. Taking readings of the temperature of the transformers
3. Taking readings from the surge arrester gauge of any recent surge
4. Inspecting the batteries in the battery bank for any corrosion on their terminals

Inspection of the protection panel

 CHAPTER 5

CHALLENGES OF SIWES

1.We were not given proper safety kit which limited the level of work to be done at the
various stations

2. The time scheduled for work was always delayed due to transportation problems

3.there were system collapses from time to time which stopped the flow of work

5.1 RECOMMENDATIONS
I would recommend that various safety equipment’s should be given to the students in
order to prevent any form of accident while working at any switchyard and vehicles
should always be on ground and punctual to convey workers to the various work stations
and the time scheduled for work should be followed strictly
5.2 CONCLUSION

In conclusion the industrial training was a success and a lot was gained in the few months I
spent at TCN Akangba sub region I was able to have a clearer sight and understanding of what I
was taught in school
REFERENCES

 Electrical 4 u.com
 Google.com
 Tcn. Akangba
 Siwes jottings