REPORT ON STUDENT INDUSTRIAL WORK EXPERIENCE SCHEME

HELD AT

TRANSMISSION COMPANY OF NIGERIA

330/132KV STATION

IKEJA WEST SUB REGION,

IPAJA AYOBO, LAGOS STATE.

BY

WAHAAB FATAI ADISA

MATRIC NO: 12/57PH/106

A PROPOSAL SUBMITTED

TO

DEPARTMENT OF PHYSICS AND MATERIAL SCIENCE

COLLEGE OF PURE AND APPLIED SCIENCES

NOVEMBER 2015

.

1

CERTIFICATION

This is to certify that Wahaab Fatai Adisa with matriculation number 12/57ph/106

of the department of Physics and Material Science, Kwara State University,

Malete has successfully undertaken his SIWES program and that this report is

originally written by him.

............................. ................................

Mr. FALUYI DATE

(Supervisor)

............................. .................................

Prof. AINA DATE

(Head of department)

............................. .................................

Mr. ADEGOKE DATE

(Industry based supervisor)

2

REPORT OVERVIEW

This report is based on Student Industrial Work Experience Scheme (SIWES)

undertaken at the 330/132KV transmission station of Ikeja West Sub Region,

located at Ipaja Ayobo, Lagos State. Being one of the sub stations of the

Transmission Company of Nigeria (TCN) the company’s core functions include

the provision and management of transmission services, system and market

operations.

This report encompasses the totality of technical exposure and workplace

experience garnered from the core departments which inludes; Electrical Main-

tenance Department (EMD), Protection, Control and Metering (PCM) and

Lines department in the station. This report also give the basic maintenance

and safety procedures, especially in the switch yard.

Activities at the Transmission stage of electricity generation and distribution

which is at the intermediate position of the entire cycle is the main focus of this

report.

3

ACKNOWLEDGMENT

All Glory be to Almighty Allah the Lord of the universe for his infinite mercies

on me, and peace be unto prophet Muhammad (S.A.W), his household and all

his companions among mankind.

I sincerely appreciate the contributions of all my supervisors and the whole

maintenance staff at Ikeja West for their thorough supervision and guidance of

my SIWES, which really made the program a quality and fulfilled one for me.

May Almighty Allah bless and reward them accordingly(Ameen).

My sincere gratitude and appreciation goes to the entire household of Alhaji

Abdulwahab Adigun for the invaluable love, concern,guidance, moral and fi-

nancial support, prayers and encouragement bestowed on me. May Almighty

Allah spare their lives and reward them abundantly (Ameen).

4

Contents

TITLE PAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1 INTRODUCTION 8

1.1 Background of SIWES . . . . . . . . . . . . . . . . . . . . . . . 8

1.2 Aims and Objectives of SIWES . . . . . . . . . . . . . . . . . . 8

1.3 Impacts and Importance of SIWES on Students Life . . . . . . . 10

2 DESCRIPTION OF TRANSMISSION COMPANY OF NIGE-

RIA (TCN) 12

2.1 Location and Brief History of Transmission Company of Nigeria 12

2.1.1 TCN 330/132kV Station Ikeja West Sub Region . . . . . 14

2.2 Organizational Structure of TCN- Ikeja West . . . . . . . . . . . 15

2.3 Departments and their Functions . . . . . . . . . . . . . . . . . 16

3 DESCRIPTION OFWORKDONE AND EXPERIENCE GAINED

DURING THE SIWES PROGRAM 20

3.1 Electrical Maintenance Department . . . . . . . . . . . . . . . . 20

3.2 Protection, Control and Metering Department . . . . . . . . . . 27

3.3 Lines Department . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4 DETAILED DESCRIPTION OF THE EQUIPMENTS USED,

THEIR FUNCTIONS AND USAGE 32

5

5 SUMMARY, CONCLUSION AND RECOMMENDATION 38

5.1 Challenges Encountered . . . . . . . . . . . . . . . . . . . . . . 38

5.2 Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5.3 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

6

List of Figures

2.1 Ikeja West Switch Yard . . . . . . . . . . . . . . . . . . . . . . . 14

2.2 Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.1 Installation of 110V Battery Bank . . . . . . . . . . . . . . . . . 22

3.2 Suge Arrester . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.3 Gas Circuit Breaker . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.4 Views of Oil Circuit Breaker . . . . . . . . . . . . . . . . . . . . 27

3.5 Current Transformer . . . . . . . . . . . . . . . . . . . . . . . . 28

3.6 Current Transformer Analysis . . . . . . . . . . . . . . . . . . . 29

4.1 Primary Current Injection Test Set . . . . . . . . . . . . . . . . 32

4.2 Gas Leakage Detector . . . . . . . . . . . . . . . . . . . . . . . . 33

4.3 Views of the Oil Dielectric Test Set . . . . . . . . . . . . . . . . 34

4.4 How Thermovision Camera works . . . . . . . . . . . . . . . . . 35

4.5 Electrical Toolbox . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.6 Current Transformer Analyzer . . . . . . . . . . . . . . . . . . . 36

4.7 Omicron CMC356 . . . . . . . . . . . . . . . . . . . . . . . . . . 37

7

Chapter 1 INTRODUCTION

1.1 Background of SIWES

The Students Industrial Work Experience Scheme (SIWES), is a skills devel-

opment program initiated by the Industrial Training Fund (ITF), in 1973 to

bridge the gap between theory and practice among students of engineering and

technology in Institutions of Higher Learning in Nigeria. It provides for on-the-

job practical experience for students as they are exposed to work methods and

techniques in handling equipment and machinery that may not be available in

their Institutions.

At inception in 1974, the Scheme started with 784 Students from 11 Institu-

tions and 104 eligible courses. By 2008, 210,390 Students from 219 Institutions

participated in the Scheme with over 112 eligible courses.

One of the primary goals of the SIWES is to help students integrate leadership

development into the experiential learning process. Students are expected to

learn and develop basic non-profit leadership skills through a mentoring rela-

tionship with innovative non-profit leaders.

By integrating leadership development activities into the Industrial Training

experience, we hope to encourage students to actively engage in non-profit

management as a professional career objective.

1.2 Aims and Objectives of SIWES

The following are some of the objectives of SIWES:

8

1. SIWES will provide students the opportunity to test their interest in a

particular career before permanent commitments are made.

2. SIWES students will develop skills in the application of theory to practical

work situations.

3. SIWES will provide avenue for students in institution of higher learning to

acquire industrial skills and experience in their course of study.

4. SIWES students will develop skills and techniques directly applicable to

their careers.

5. SIWES will aid students in adjusting from college to full-time employment.

6. SIWES will provide students the opportunity to develop attitudes conducive

to effective interpersonal relationships.

7. SIWES will increase a student? sense of responsibility

8. SIWES students will be prepared to enter into full-time employment in

their area of specialization upon graduation.

9. SIWES students will acquire good work habits.

10. . SIWES students will develop employment records/references that will

enhance employment opportunities.

11. SIWES Students will be able to outline at least positive specific goals with

several staff members by comparing performance with job duties and de-

velop a draft plan with staff to accomplish performance needs, supervision

plan and rewards.

12. SIWES will provide students the opportunity to understand informal orga-

nizational interrelationships.

9

13. SIWES Students will be able to develop a draft agency or project budget

and will be able to identify methods of obtaining revenue to support the

budget.

14. . SIWES Students will be able to develop a model policy that gives current

front-line leaders the permission and expectation to work with other staff on

convict resolution and explain how this works to current front line leaders.

15. SIWES Students will be able to describe different skills leaders can use

to foster commitment and collaboration with both internal and external

constituents.

The above objective of SIWES shows that proper implementation by institution

and industries will help to ascertain the student level of practical capability in

line with the business ethics and characteristics in office environment.

1.3 Impacts and Importance of SIWES on Students Life

Science students need actual work experience and technical exposure in order

to fit in to the ever advancing technological era we are in. Industrial training

will enable students to learn how to apply theories learnt in school to real life

situation in order to appreciate the value of science.

1. Students learn how to apply the latest technology in their professional call-

ings.

2. It helps to develop entrepreneurship skills in the students.

3. To expose students to critical skills, quality control measure and safety

regulations in their field of work.

10

4. To control characters, morals and relationship of students towards work

11

Chapter 2 DESCRIPTION OF TRANSMISSION COMPANY OF NIGE-

RIA (TCN)

2.1 Location and Brief History of Transmission Company of

Nigeria

As part of the evolution in the power industry in Nigeria, the Federal Govern-

ment by Decree No.24 of 1972 created the National Electric Power Authority

(NEPA). This was consequent upon the merger of the Electricity Corporation

of Nigeria (ECN) and Niger Dams Authority (NDA).

In September 1990, the partial Commercialization came into being with the

appointment of a Managing Director/Chief executive to superintend over the

corporation. Also, the Authority was divided into four autonomous divisions

namely: Generation and Transmission; Distribution and Sales; Engineering; Fi-

nance and administration. Each division was headed by an Executive Director.

The Federal Government of Nigeria (FGN) took further steps towards the

Restructuring of the Nigerian Power Sector to establish an electricity supply

that is efficient, reliable and cost-effective throughout the country and which

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 eleven (11) Distribution Companies, six (6) Generation Companies and one

(1) Transmission Company.

The Transmission Company of Nigeria (TCN) is one of the eighteen (18)

successors of the unbundled PHCN following the conclusion of the privatization

12

in November 2013, and is the only company that the Federal Government retain

ownership of, currently an asset under the custodianship of the Federal Ministry

of Power, it will initially remain publicly owned. TCN is responsible for:

• the management of operation

• maintenance and expansion

of the 132kV and 330kV transmission system. The Bureau of Public Enterprise

(BPE) recently appointed a management Contractor, Manitoba Hydro Inter-

national (MHI) for TCN which took over the functions of Transmission Service

Provider(TSP), System Operator(SO) and Market Operator to undertake the

overall management of TCN.

TCN’s operations cover the whole country and administratively it is divided

into 8 Transmission Regions: Benin, Enugu, Port-Harcourt, Bauchi, Kaduna,

Shiroro, Osogbo and Lagos that contain various Work Centers amongst which

are:

• Ikeja West W/C

• Shiroro W/C

• Akangba W/C

• Ganmo W/C

• Papalanta W/C

• Egbim W/C

• Jebba W/C

13

2.1.1 TCN 330/132kV Station Ikeja West Sub Region

Ikeja West Sub Region is a 330/132kV Transmission Station located at Ayobo

Ipaja Lagos under the Lagos Region, the station contains one of the Regional

Control Centers (RCCs). There are five 150MVA transformers in the Switch

Yard (as at the time of this report) of which two are connected in parallel and

the other three also connected in parallel making up two bus bar, two reactors

and of course a Control room. The Station receives electricity supply at 330kV

(primary) receiving end of the Switch Yard from Generating Station, steps it

down with the help of the step down transformers and feed the Transmission

Sub Stations at 132kV at the (secondary) sending end of the Switch Yard.

The station feeds various sub stations like Agbara TS, Ayobo TS, Ogba TS,

Alausa TS and Alimosho TS 132KV with a monitored frequency of 50Hz to

mention a few. Transmission services comes in between the Generating Station

and Distribution Stations and it involves many stages and various protection

in place.

Figure 2.1: Ikeja West Switch Yard

14

Figure 2.2: Control Panel

2.2 Organizational Structure of TCN- Ikeja West

Below is the Organizational structure of TCN Ikeja West Sub Station.

AGM(T)

HR( SM) SCADA (AGM ISO) PM (T)

Security

Canteen Service

Transport

COMM (PM)

ISO

AYOBO (TS)

PCM (SM)

EMD (SM)

LINES (SM)

TRANSPORT

ISO

HSE (Officer 1)

KEY:

• AGM (T): Assistant General Manager (Transmission)

• PM (T): Principal Manager (Transmission)

15

• HR (SM): Human Resources (Senior Manager)

• SCADA: Supervisory, Control and Data Acquisition

• COMM (PM): Communication (Principal Manager)

• ISO: Integrated System Operations

• EMD: Electrical Maintenance Department

• PCM: Protection, Control and Metering

• HSE: Health Safety and Environment

• TS: Transmission Station

2.3 Departments and their Functions

There are five main Departments as listed below:

1. Electrical Maintenance Department (EMD)

2. System Operation

3. Protection, Correction and Metering Department (PCM)

4. Lines

5. Communication

According to the Company policy, SIWES and IT students are usually posted

to all the aforementioned departments in order to gain the maximum experi-

ence possible and to understand the duties of the various departments and the

Station as a whole, so by implication I was posted to all the maintenance and

operations departments in the order of the list below. Below are the functions

16

of the various departments:

ELECTRICAL MAINTENANCE DEPARTMENT

The Electrical Maintenance Department as a maintenance department is con-

cern with

• Installation

• Repair

• Maintenance

of the various electrical devices (e.g transformer,circuit breaker, isolator, etc.).

The department is responsible for the maintenance of all the electrical equip-

ment in the station and other attached sub station. On various occasions the

EMD do go to other sub stations like Alimosho TS, Ogba TS, Agbara TS,Alausa

TS, etc that receive power from Ikeja West Station in other to maintain, repair

and install electrical devices.

PROTECTION, CONTROL AND METERING DEPARTMENT

This is a technical department saddled with the responsibility of ensuring

correct and efficient protection of the various component and devices in the

station, because prevention is not only better than cure, it is also cheaper. The

department actualizes this by carrying out correct circuit connection, installa-

tion,programming and wiring of protection and metering devices like Circuit

Breaker, Current Transformers, Relay and so on and complete installation of

17

other protective equipments, which is why the department always work with

their Circuit Diagram designed by the manufacturer of the device being worked

on like Crompton greaves, Areva, and so on. The department also conducts

various scheduled maintenance and tests on power equipments.

LINES DEPARTMENT

This department is concerned with monitoring and maintaining the trans-

mission lines from the station to the designated substation. The department

carries out its duty by conducting scheduled inspection. Patrol on different

lines during which the sky wires, conductors, insulators and the transmission

towers as a whole are inspected for any fault and fix any such anomaly on the

line or transmission tower.

SYSTEM OPERATION

The main responsibility of the System Operator is to operate the transmission

system by monitoring and operating switching devices like breaker, isolators,

e.t.c in a safe and reliable manner. Its function also includes load shedding,

granting of outage permit for the maintenance crew, taking load and energy

readings and so on.

COMMUNICATION DEPARTMENT

This department is responsible for communication between transmission sta-

tions and National Control Center (NCC), maintenance of the 48V battery

18

bank used for communication, Power Line Carrier Communication(PLCC), in-

spection for fault in the control room and filling of trouble report.

19

Chapter 3 DESCRIPTION OFWORKDONE AND EXPERIENCE GAINED

DURING THE SIWES PROGRAM

Activities and Work done at the Various Departments

As outlined earlier I was posted to all the five core departments in order to

experience and take part in all the various activities.

3.1 Electrical Maintenance Department

Starting with the Electrical Maintenance Department which was actually my

first department in the station, the activities of the this department encom-

passes installation, maintenance and repair of electrical devices.

INSTALLATIONS

Installation is a process whereby a system with parts and accessories are

assembled and fixed(connected) to make the system ready for operation, below

are the installation work i took part in.

Installation of Battery Bank

Battery Bank-the heart of the station.

Firstly, i would like to clarify the concept of Battery Bank. A battery is a

connection of two cells, while a battery bank is the connection of above two

cells.

In other to make a battery bank of 110V,400Ah(DC), 55 pieces of cell each

rated 2V,400Ah were made available.The cells were arranged on a pallet in the

battery house in a series connection,that is positive terminal of a cell connected

20

to the negative terminal of the next cell.After having attained a tight connec-

tion, a multimeter (also referred to as AVO meter ) was used to measure the

actual individual voltage and this individual voltages were summed up to obtain

110V total voltage.

The 110V battery bank is used as a backup for the operations of various equip-

ment in the station that makes use of direct current,like the Circuit breaker,

Isolator, Relay, e.t.c. There is also a 48V battery bank that also supplies the

required DC supply to the Alarms and also for communication. These battery

banks are constantly charged to full capacity by the associated charger,these

battery banks supply the equipment by converting the AC supply from the

battery charger to the required DC while still on charging mode. This process

is maintained until there is system collapse whereby the whole station looses

supply, the battery bank then pick up the task by supplying it’s stored current

to the vital equipment.

21

Figure 3.1: Installation of 110V Battery Bank

Installation of Polymer-housed Metal Oxide surge Arrester without

Gaps for 330/132kV Autotransformer

A Surge Arrester is a device designed to protect electrical equipment from tran-

sient over-voltages, to limit the duration and amplitude of the follow current.

It is normally connected between line and earth and close to the equipment it

is to protect(usually transformers).

• It should behave as a perfect insulator for the highest system voltage to

ground.

• It should discharge any over-voltage into the ground safely.

• It should restore itself as an insulator after discharging the excess voltage.

The new Surge Arrester’s resistance was first tested with the High Voltage

Insulation Tester(Mega) in order to ascertain the capability of the equipment to

22

serve its purpose, after which its base was fixed on the supporting base structure.

The Surge Counter was installed in series between the Surge Arrester and earth,

lines connection was made ensuring continuity in the wires, the Arrester and

Surge Counter was properly earthed.

Figure 3.2: Suge Arrester

REPAIR

Circuit Breaker: A circuit breaker is an electrical device used as a switch

(to open and close ) for power entering a line under normal and abnormal

condition.It can also be used to feed a line. Circuit breakers are classified based

on different criterion.

• According to their Quenching Medium

1. Air circuit breaker

2. Oil circuit breaker

3. Vacuum circuit breaker

23

4. SF6circuitbreaker

• According to their Services

1. Outdoor circuit breaker

2. Indoor circuit breaker

• According to the Operating Mechanism

1. Spring operated circuit breaker

2. Pneumatic circuit breaker

3. Hydraulic circuit breaker

• According to Voltage level of Installation

1. High Voltage circuit breaker

2. Medium Voltage circuit breaker

3. Low Voltage circuit breaker

Overhaul of Gas Circuit Breaker

We repaired the Alimosho Line2 Outdoor Gas circuit breaker whose operating

mechanism (hydraulic: compressed oil) was faulty by first earthing the line with

the earthing cable, then the gas pressure was released and likewise the oil of

the operating mechanism(Hydraulic). The three moving part of the operating

mechanism was removed and replaced with a better one, because the former

has been blocked with some particles that thwarted its normal operation.

Finally, the breaker was coupled and the gas refilled back to 6.2kg and also

the oil siphoned back into the accumulator.The Leakage Detector was used to

inspect the breaker for any leakage of the gas before it was put back to work

24

after it has passed the leakage test.

Figure 3.3: Gas Circuit Breaker

The significant of the overhaul is summarized below:

• To achieve the normal operation of closing and/or opening of the circuit

breaker.

• To hold the circuit breaker in closed position by toggles or latches until the

tripping signal is received.

• To allow the circuit breaker to open without delay immediately on receiving

tripping signal.

• To perform the auto-reclosure cycle (if installed or fitted on CB).

• To perform the related functions such as indication and control

General Maintenance of Isolator

Isolator is an electrical device used to break or stop the flow of current.

We carried out the general maintenance of the nine gang isolator and reactor

isolators at the 330kV receiving end in the switch yard. After obtaining the

guarantee item and permit to work, the lines were opened and de-energized,

25

and earthed with the earthing cable. All the movable part of the isolators

were lubricated, the contact points thoroughly brushed and greased to avoid

corrosion.

MAINTENANCE

Maintenance of Indoor Oil Circuit Breaker

As part of the duties of the EMD crew, we carried out the maintenance of

the 132kV indoor oil circuit breaker at Alimosho station. The first step was

to test the interrupter’s insulation with an instrument known as High Voltage

Insulation Tester(usually called Mega),then the oil tank was pulled out in order

to siphon out the carbonated oil. Then the interrupter slot extending to the

oil tank and the oil tank itself were thoroughly cleaned and rinsed with a new

transformer oil before replacing the new transformer oil to the oil tank.

Finally another insulation test was done to ascertain the ability of the breaker

to withstand the high voltage without damage and it gave the required reading

on all the interrupters.

(a) Oil Circuit Breaker (b) Oil Circuit Breaker

Figure 3.4: Views of Oil Circuit Breaker

26

3.2 Protection, Control and Metering Department

There are also very crucial work experience I gained in the Protection, Control

and Metering department (PCM), entailing various tests, maintenance, obser-

vations and installations.

Protection Tests

Primary Current Injection Test on Current Transformer(CT)

The Current Transformer(instrument transformer) is a Metering and Pro-

tection transformer, they are used with ammeters, watt meters, power-factor

meters, watt-hour meters, compensators, protective and regulating relays and

the trip coil of circuit breakers. One current transformer can be used to operate

several instruments, provided that the combined burden does not exceed that

for which the transformer is designed and compensated. The current trans-

former is connected directly in series with the line.

Figure 3.5: Current Transformer

27

The primary current injection test is a pre-commissioning test on CT carried

out by supplying a quantity of current (60A) through the test set(PCITS) to

the primary side of the CT and taking the value of the output current at the

secondary side. This is done for the three CT’s on the three phases of the

line. The CT has a rated turns ratio of 2000:1A, meaning an input of 2000A of

current through the primary delivers 1A through the secondary side.

The purpose of the test is to practically ascertain the turns ratio of the current

transformer, the observed readings were compared with the theoretical value

calculated using the formula below:

xA =1AX60A

2000A= 30mA (3.1)

The test was also carried out on the secondary feeder breaker to ascertain the

maximum volt it can withstand.

28

Current Transformer Analysis

The current Analyzer is an equipment used to analyze the current transformer,

it analyzes and display various information about the current transformer like;

turns ratio,power factor, burden Voltage,e.t.c. The test set was connected to

a DC power supply(240V) and used to analyse the three cores of the current

transformer, the required settings was also done and the test set showed the

condition of the cores and the result saved in the test set’s memory.

Figure 3.6: Current Transformer Analysis

Oil Insulation Test

The Oil Insulation test was carried out on various samples of transformer

oil in order to confirm if they are fit to be used as insulating medium in high

voltage devices(Transformer, Grounding Transformer, Breaker, e.t.c).

The test was conducted using the Oil Dielectric Test Set, the oil test sample

was poured into the small container of the test set, rinsing the container with

small portion of the oil before filling the container up to required level and the

29

container placed in the test set. A voltage rise of 2kV/s was applied for a gap

of 2.5mm between the two electrodes in the oil sample. The test gives the the

dielectric breakdown voltage of the oil sample, that is, the voltage at which the

oil insulation breaks down and becomes conducting. The test was repeated five

more times for each oil sample, in an interval of five minutes between successful

tests and there average taken.

Test S/N Sample GT15 Sample GT17 Sample GT20 Sample T4

1 10.4 45.4 37.6 16.7

2 20.8 41.6 28.2 18.3

3 24.2 44.2 32.2 18.3

4 23.2 33.8 30.8 14.0

5 31.1 34.8 36.6 15.2

6 28.6 36.4 38.8 12.8

Average 23.05kV/mm 39.37kV/mm 34.63kV/mm 15.88kV/mm

Table 3.1: Oil insulation test result

The purpose of the test is to confirm if the oil insulation strength is within

the required value range, normally not less than 30kV/mm to know if the oil is

still suitable for further use.

3.3 Lines Department

This department is concerned with monitoring and maintaining the transmis-

sion lines from the station to the designated sub station.

Inspection of Agbara Station for Hot Spot Using Thermovision Camera

30

A thermovision camera (thermal imaging camera) is a device that forms an

image using infrared radiation, similar to a common camera that forms an image

using visible light. Instead of the 450750 nanometer range of the visible light

camera, infrared cameras operate in wavelengths as long as 14,000 nm (14 m).

The higher an object’s temperature, the more infrared radiation is emitted as

black-body radiation.

The transformer and conductors at Agbara station was inspected with the

thermovision camera in order to detect hot spots that needs to be attended

to in other to avoid any pending danger that might occur as a result of the

abnormal temperature.

Replacement of Detached Conductor and Burnt Clamp on the Wave trap

Firstly, Wave Traps are used at sub-stations using Power Line Carrier Com-

munication (PLCC). PLCC is used to transmit communication and control

information at a high frequency over the power lines. This reduces need for a

separate infra for communication between sub-stations.

A conductor on the wave trap at the 132KV side of Ikeja West switch-yard got

burnt and detached from fault returning from the secondary side, the associated

clamp was also burnt and welded. The line was first discharged and earthed

before the burnt clamp was removed, the plate cleaned and filed before replacing

it with a new one. The detached cable was also connected back to the clamp.

31

Chapter 4 DETAILED DESCRIPTION OF THE EQUIPMENTS USED, THEIR

FUNCTIONS AND USAGE

There are various equipment used in each departments,especially in the Elec-

trical Maintenance Department, the Protection, Control and metering Depart-

ment and Lines viz:

Primary Current Injection Test Set (PCITS)

The PCITS is a computerized electrical equipment used to ascertain the turns

ratio of the primary to secondary. The equipment uses alternating current sup-

ply (230V DC) to operate, the test set is used to inject a measured current to

the primary of the CT while the output Volt is measured from the secondary

in order to confirm the turns ratio.

Figure 4.1: Primary Current Injection Test Set

Gas Leakage Detector

The Gas Leakage Detector (also known as Sniffer) is a device used to detect

leakage of gas from the cylinder and the entire breaker to avoid wastage of the

gas.

32

Figure 4.2: Gas Leakage Detector

Oil Dielectric Test Set

The Oil Dielectric Test Set is an equipment used to measure the dielectric

strength of insulating oil (transformer oil) which is an implication of the in-

sulating property of the oil. The test set operates with alternating current, it

contains a small oil container in which there are two electrodes with a gap be-

tween them. The test set has a LED display system and various control buttons

like start, pause, stop, e.t.c.

The test set works by placing the sample to be tested in the small container

which is then placed into the test set, with the gap between the electrode been

set to the required test specification. Then a voltage difference rise of 0.5kV/s,

2kV/s, 3kV/s depending on the test specification is applied across the electrode

in the oil sample. By switching on the set and clicking the start button, the

voltage difference across the electrode in the oil sample begin to rise until the

33

dielectric breakdown voltage of the oil is reached, at this instance the LED

display unit display and hold the breakdown voltage.

(a) Oil Dielectric Test Set (b) Oil Dielectric Test Set

Figure 4.3: Views of the Oil Dielectric Test Set

Thermovision Camera

A Thermovision Camera (also called an infrared camera or thermal imag-

ing camera) is a device that forms an image using infrared radiation, similar

to a common camera that forms an image using visible light. Instead of the

450750 nanometer range of the visible light camera, infrared cameras operate

in wavelengths as long as 14,000 nm (14 m).

Generally speaking, the higher an object’s temperature, the more infrared

radiation is emitted as black-body radiation. The Thermovision Camera can

detect this radiation in a way similar to the way an ordinary camera detects

visible light. It works even in total darkness because ambient light level does

not matter.

The device is put to use in order to detect areas of high temperature (hot-

spot) by first selecting the desired theme and also a specific value is required

as the environment temperature which the device will use as a criterion for

34

determining region of high, low or normal temperature. The device will then

form an image displaying various color which can be looked up in the color code

set of the theme in use, with this the hot-spots are detected.

(a) Thermovision Camera (b) Detection of Hot-spot

Figure 4.4: How Thermovision Camera works

Electrical Tool Box

The tool box is an essential part of the maintenance equipment containing a

wide range of tools such as different sizes of spanner for loosening and tighten-

ing bolt and nut, screw driver to loose or tighten screws, arc saw for cutting

metallic materials, pliers and cutter for cutting and knotting cable wire, insu-

lation tape, paper tape and so on.

Figure 4.5: Electrical Toolbox

35

Omicron Current Transformer Analyzer

Omicron CT Analyzer is a device used to analyze and determine the status of

a current transformer, ranging from power factor, turns ratio, core balance and

so on. CT Analyzer works with three phase (415V AC) power supply, and it has

three pairs of cable connected across the cores of the current transformer being

analyzed, after making the required connection, some preliminary settings are

required like giving the nomenclature of the CT, its location and station after

that the analyze button is clicked for the process to begin. The device also has

an external storage in which it stores the the data of the analyzed CT which

can be removed and stored in a Laptop for easy assess to the data when needed.

Figure 4.6: Current Transformer Analyzer

Omicron CMC356

Omicron CMC356 is a versatile device that can be used to simulate current

and voltage through a relay to trip test a breaker when conducting a test. This

device works with a software installed on a PC and also makes use of three

phase supply, it has one voltage output and two current output. It is usually

put to use when installing or maintaining a protection relay like overcurrent or

differential relay in which case the software on the PC is used to set the amount

36

of current required, while the trip current has been set on the relay. With the

current output of the Omicron connected to the input of the relay, the required

current is then simulated through the relay. In the case of a distance relay

that makes use of both voltage and current, both voltage and current output

of Omicron CMC356 is connected to the voltage and current input of the relay

respectively.

Succinctly put, Omicron CMC356 acts like Voltage transformer(VT) and Cur-

rent transformer(CT) under test condition to supply the current and voltage

required for the relay to operate that would have be supplied by the real VT

and CT under normal condition.

Figure 4.7: Omicron CMC356

37

Chapter 5 SUMMARY, CONCLUSION AND RECOMMENDATION

It is indeed a worthwhile experience in general, considering my level of involve-

ment in some technical work and being able to witness the various application

of the theoretical aspect of education which i am conversant with. I also got to

understand the process of generating, transmitting and distributing electricity

which is a nucleus of most of our activities during this program.

5.1 Challenges Encountered

Although my SIWES program has been a fulfilled one it is not without its own

challenges. The most challenging issue is that SIWES student are not allowed

to take part in some technical work especially when it requires climbing tower

or gantry in the switchyard due to the fact that are not insured, because all the

staff have been insured against any hazard that might occur in the switchyard

and the station at large.

Part of the challenges is also the fact that some of the staff don’t really want

to involve SIWES student when doing the less dangerous work that are also

technical, sometimes we had to beg our way through so as to get the experience

while they gladly call upon us anytime they have a laborious work like having

to transfer battery cells from one battery room to another.

5.2 Recommendation

I recommend that a mechanism that would enable students to get a place of

attachment early be put in place because some student have to stay at home

up to a month or thereabout before finally getting a place of attachment. I

38

also recommend thorough supervision of student so that they can have full

involvement in the technical work in order to appreciate the application of

their theoretical knowledge.

5.3 Safety

There is popular quote that says ”Working safely is like breathing, when you

stop you die”. In view of this there is a safety policy in the station whereby

before any maintenance work is done the maintenance department first collect

permit from the operator in the control room who makes sure to isolate the line

which is to be maintained. The maintenance crew having collected the permit

can then go into the switchyard to work.

Even with the fact that the line has been isolated there is still presence of

residual charge enough to knock a man down due to high voltage that was

passing through the conductor, this is where the maintenance department also

ensure safety of the workers by first discharging the line with the grounding

cable and then earthing the line either with permanent or temporary ground

so that any dangerous voltage flows to the ground without hurting the person

working on the line.

5.4 Conclusion

This program has made me realize the importance and usefulness of the theory

thought in school and the versatility of physics. The program has also imbibe

good working ethics in me because i had to work with different set of people,

and i can handle some equipments efficiently all thanks to this program.

39