INDUSTRIAL TRAINING REPORT - II

TRAINING ORGANIZATION DIMO (PVT) LIMITED

PERIOD OF TRAINING FROM: 20.10.2014 TO: 11.01.2015

FIELD OF SPECIALIZATION ELECTRICAL & ELECTRONIC

ENGINEERING

THUSHAN S.

E/10/361

i

Acknowledgements

It is a great pleasure to acknowledge the assistance of many people after having a great training with

the key professionals in the field of Electrical Engineering.

First of all I would like to take this opportunity to express my gratitude to all ladies and gentlemen

who have given their maximum involvement to complete the Industrial Training Session at Dimo (Pvt)

Ltd Successfully. Further I would like to extend my sincere gratitude towards the following personals

that rendered their kind support to enrich my training experience. Mr. Darshna Subasinghe (General

Manager – Power Solution Division, Dimo (Pvt) Ltd), for arranged the training at Dimo (Pvt) Ltd and

Mr. Nalin De Silva (Project Manager, Dimo (Pvt) Ltd) for his kind contribution in my training, At last

I would like to convey my heartiest thanks to Project Engineer, Electrical Engineers and all other staff

of Power Solution Division of Dimo (Pvt) Ltd.

Finally I would like to express my sincere gratitude to National Apprentice and Industrial Training

Authority (NAITA) for providing us the facilities to undergo a well standard training session, to

Industrial Training and Career Guidance Unit (ITCGU) of Faculty of Engineering as well as the Staff

of Department of Electrical and Electronic Engineering for guiding me throughout the training period.

Thank You,

S. Thushan,

Faculty of Engineering,

University of Peradeniya.

ii

CONTENTS

Acknowledgments i

Contents ii

List of Figures iii

List of Tables iv

List of Abbreviations v

Chapter 1 INTRODUCTION 1

1.1 Introduction of my training session 1

1.2 Introduction of DIMO 2

1.3 Engineering Services of Power Engineering Division 3

Chapter 2 WORK SITES 5

2.1 Introduction 5

2.2 General Overview of Project Sites 5

2.3 Standard Bidding for a Project 8

2.4 General Overview of Maintenance Sites 9

Chapter 3 INSTRUMENTS 12

3.1 Introduction 12

3.2 Transformers 12

3.3 Switchgears 15

Chapter 4 TECHNIQUIES USED 18

4.1 Introduction 18

4.2 Earth System 18

4.3 Cable Termination 22

4.4 Unloading Methods 23

Chapter 5 STANDARDS AND TESTS 24

5.1 Introduction 24

5.2 Testing and Commissioning 24

5.3 FAT 25

Chapter 6 SERVICES OF DIMO 27

6.1 Introduction 27

6.2 HV Panel 27

6.3 Transformer Service 28

6.4 Protection Relay Testing 28

6.5 Thermal Imaging 29

Chapter 7 CONCLUSION 30

iii

LIST OF FIGURES

Figure.1. 1 DIMO Logo 2

Figure.1. 2 Organization Chart of Power Solutions Division 4

Figure.2.1 Transformer and Switchgear of the Mobitel Site- welikada 5

Figure.2.2 Transformer and Switchgear of the Galle Face Hotel 6

Figure.2.3 Transformer and Switchgear of RIL Site 7

Figure.2.4 Transformer of Navy Base at LTL 8

Figure.2.5 Railway Crossing Signal Controlling System, Kosgama 10

Figure.2.6 Blasted Switchgear in HSBC Head Office 10

Figure.2.7 Collecting Oil Sample in Holsim-Puttalam 11

Figure.2.8 Oil Testing on Transformer 11

Figure.3.1 LTL transformers 12

Figure.3.2 Vacuum Circuit Backer Switchgear (8BK88 PLUS) 16

Figure.3.3 Compartments of 8BK88 PLUS 17

Figure.3.4 Circuit Breaker (Moveable) 17

Figure.4.1 Method of Connecting Equipment in Wenner Method 19

Figure.4.2 Method of Connecting Equipment in Schlumberger Method 20

Figure.4.3 Method of Connecting Equipment in Fall-of-Potential Test 20

Figure.4.4 Method of Connecting Equipment in Selective Testing 21

Figure.4.5 Test Current Paths in the Stakeless Method 21

Figure.4.6 Procedure for Cable Termination 22

Figure.4.7 Unloading of LTL Transformer 23

Figure.4.8 Unloading of TRAFO Cast-Resin Transformer 23

Figure.4.9 Unloading of SIMENS Switchgear 23

Figure.6.1 Thermo Graphic Images of Power System 29

iv

LIST OF TABLES

Table 3.1 Detail of the LTL Transformers 13

Table 3.2 Detail of the TRAFO Transformers 14

Table 3.3 Electrical data (Maximum Values) of 8BK88 PLUS 16

v

LIST OF ABBERVIATIONS

ABBREVIATIONS DESCRIPTION

CB Circuit Breaker

CT Current Transformer

DIMO Diesel & Motor Engineering PLC

EMF Electro Motive Force

EMI Electro Magnetic Interference

FAT Factory Acceptance Test

HSBC Hongkong Shanghai Banking Corporation

HV High Voltage

IEC International Electro technical Commission

IEEE Institute of Electrical & Electro Engineers

IFB Invitation for Bids

LTL Lanka Transformer Limited

LV Low Voltage

MV Medium Voltage

PCB Poly Chlorinated Biphenyl

RFI Radio Frequency Interference

RIL Ready ware Industry Limited

RMS Root Mean Square

SPI Secretariat of Personal Identification

VT Voltage Transformer

1

CHAPTER 01-INTRODUCTION

1.1 INTRODUCTION OF MY TRAINING SESSION

Under the course TR400-Industrial Training I was assigned as an apprentice at DIMO (Pvt) Ltd Power

Engineering Department. for a period of 12 weeks, from 20/10/2014 to 11/01/2015 by the Industrial

Training and Career Guidance Unit (ITCGU) of the Faculty of Engineering, University of Peradeniya

in collaboration with National Apprentice and Industrial Training Authority (NAITA). The training

places which were given to me are mentioned below.

PROJECT SITES

1. Mobitel, Welikada

2. Galle Face Hotel, Colombo

3. RIL, Colombo

4. Navy Base, Mullikulam

MAINTENANCE PLACES

1. German Cultural Centre

2. Shamudhra Hotel, Ghoshoda

3. SPI, Bathramulla

4. Railway Crossing, Kosgama

5. HSBC, Head Office

6. Holsim, Puttalam

7. Iceland Resident

2

1.2 INTRODUCTION OF DIMO

Diesel & Motor Engineering (Pvt) Ltd is a subsidiary of Diesel & Motor Engineering PLC which is a

leading company in Sri Lankan business arena. It is well known among people casually as “DIMO”.

Diesel & Motor Engineering Company Limited was founded in 1939 with a staff of 29. This focus

continued till 1945 when DIMO was incorporated as a Private Limited Liability Company. In 1964 it

was converted into a Public Quoted Company by listing at the Colombo Brokers' Association. It’s

proud to say that DIMO is a hundred percent Sri Lankan company which is headed by Mr. Ranjith

Pandithage, The Chairman. DIMO has its businesses spread in a wide range where all of them united

under the motto of “Expect Perfection”. More than 1,200 employees around the country work hard to

make this successful journey up to now. Now DIMO is among the top 15 corporate brands in Sri

Lanka. The group turnover for the period of 2010/2011 is 44.34 billion LKR.

Fig.1.1 DIMO Logo

DIMO – ASPIRATION

To be the corporate role model that inspires and touches the life of every Sri Lankan, every day.

DIMO - PURPOSE

To create value responsibly

DIMO - VALUES

RESPONSIBLE: To be a responsible corporate citizen.

RIGHTEOUS: To stand for righteousness with resolve.

RESPONSIVE: To be approachable and responsive to every stakeholder we serve.

RELIABLE: To be reliable and trustworthy, whatever we undertake to do.

RESPECTFUL: To always treat people with dignity and respect.

RESILIENT: To be resilient in adversity.

3

DIMO – SECTORS

Vehicles

Building management System

Fluid management

Mercedes- Benz Centre of Excellence –‘DIMO 800’

Total Marine Solutions

Agriculture Machinery

Construction & Mining Machinery

Power Solutions

Total Tyre Solutions

Auto Components & Accessories

Customer Products

Lighting Solutions

Storage Systems & Material Handling

Bosch Service Centre

Engine Overhaul & Machinery

Medical Engineering

Tools & Equipment

DIMO (Pvt) Ltd –DEPARTMENTS

Building Management Systems

Power Engineering Solutions

Medical Engineering Solutions

Marine, Industrial, Construction and Rail Propulsion Systems

1.3 ENGINEERING SERVICES OF POWER ENGINEERING DIVISION

1.3.1 Power generation & Power Plant Automation

Power Plant Automation Systems

Power Generators

Renewable Power Plants (Wind Farms)

Mini Hydro Power plants

1.3.2 Power Transmission & Distribution

Indoor, Outdoor Switchgears

Battery & Battery Chargers

4

Over Head & Under Ground Power Lines (Layering & Terminations)

LV Switchgear and Panels

1.3.3 Power Quality & Energy Management Systems

Energy Audits & Solutions

Capacitor Banks

Harmonic Filter Banks

1.3.4 Lightning Protection Systems

Plant Earthing & Lighting Protection Systems

Surge Protection Systems

DIMO (Pvt) Ltd – POWER SOLUTIONS - ORGANIZATION STRUCTURE

Fig.1.2 Organization Chart of Power Solutions Division

5

CHAPTER 02-WORK SITES

2.1 INTRODUCTION

In my training Period I was assigned to work in Project sites and Maintenance Sites. Some of the

project works started before I joined the training and some of them started middle of my training

period and continued after I completed my training as well. In maintenance works are the earlier

projects of DIMO which were handed over to the customers several years back, However still DIMO

do all the necessary maintenance works for the customer satisfaction. Because of that DIMO achieved

the 88% of the customer satisfaction in 2013/2014.

2.2 GENERAL OVERVIEW OF PROJECT SITES

2.2.1 Mobitel - Welikada

There was an existing system in the Mobitel site. However it is not enough for the current demand

and future projects of the customer. Therefore DIMO was requested to implement the new system in

two phases. The plan is first complete the first phase of the project and replace a part of existing

system and continue the rest of the work. This project was started before I joined and still continue

after I completed my project. The detail of the project is given below.

Project Number: - DPS188

Capacity of the transformers: - 2000 KVA (2 transformers)

Manufacture of the transformer: - LTL (Sri Lanka)

Type of the Transformer:- Oil Immersed Transformer

Voltage: - 11KV

Panel type: - 11KV Switch Board

Manufacture of the Panel: - SIEMENS

Fig.2.1 Transformer and Switchgear of the Mobitel Site- welikada

6

2.2.2 Galle Face Hotel Refurbishment

There was an existing system in the Galle face hotel. They like to Refurbishment the system because

of the future needs and extend the hotel. This project was started before I joint the training. However

the civil work was only completed in that period. Therefore I participates the rest of the work. Here

some part of the technical works similar to the earlier Mobitel site. But I learnt some new ideas from

this project as well. The detail of the project is given below.

Project Number: - DPS 245

Capacity of the transformers: - 1000 KVA (2 transformers)

Manufacture of the transformer: - TRAFO ELETTRO (Italy)

Type of the Transformer:- TES-R

Voltage: - 11KV

Panel type: - 11KV Switch Board

Manufacture of the Panel: - SIEMENS

Fig.2.2 Transformer and Switchgear of the Galle Face Hotel

7

2.2.3 RIL – Colombo

This is the new project of DIMO. Here, there is going to start a new industry. For that DIMO install a

new medium voltage power system. DIMO is responsible only for the transformer and switchgear

parts and another company do the low voltage implementations. This project also started before I joint

the training. However the civil work only completed. I participates the installation of transformer and

switchgear. The detail of the project is given below.

Project Number: - DPS 196

Capacity of the transformers: - 2000 KVA (2 transformers)

Manufacture of the transformer: - TRAFO ELETTRO (Italy)

Type of the Transformer:- TES-R

Voltage: - 11KV

Panel type: - 11KV Switch Board

Manufacture of the Panel: - SIEMENS

Fig.2.3 Transformer and Switchgear of RIL Site

8

2.2.4 Navy Base - Mullikulam

This is a small project. I participated from the beginning of this project; however it was not completed

when I leave from DIMO. I participated for the FAT and Side test visits. It is also a new project of

DIMO. In this project the major issue is that the transportation of the equipment from Colombo to

mullikulam and environmental conditions. The detail of the project is given below.

Project Number: - DPS 205

Capacity of the transformers: - 400 KVA (2 transformers)

Manufacture of the transformer: - LTL(Sri Lanka)

Type of the Transformer:- Oil Immersed Transformer

Voltage: - 11KV

Panel type: - 11KV Switch Board

Manufacture of the Panel: - SIEMENS

Fig.2.4 Transformer of Navy Base at LTL

2.3 STANDARD BIDDING FOR A PROJECT

In DIMO getting the project from the customer, organize the project; prepare all the legal details,

contracts also the responsibility of the engineer. Therefore am also was trained briefly about this

works. For these procedures DIMO follow the ‘Standard Bidding Document’ of Sri Lanka under

national shopping procedures. Documents for bidding are given below.

Invitation for Bids (IFB)

Instructions for Bidders

Standard forms (Contract)

Letter of Acceptance

Agreement

Performance Security

Advance Payment, Security

Retention Money Guarantee

9

Conditions of Contract

Forms of Bid and Qualification Information

Bidding Data and Contract Data

Specifications

Bill of Quantities and Schedules

Drawings

Standard forms

Works cope

Milestone payment

2.4 GENERAL OVERVIEW OF MAINTANENCE SITES

2.4.1 German Cultural Centre

This is one of the older projects of DIMO. There is a generator in that place. We went to that place in

03.12.2014 for their request. There we observed an error in the controller circuit and suggested them to

change the controller circuit as soon as possible.

2.4.2 Shamudhra Hotel, Ghoshoda

This is the new project of DIMO. For this medium voltage transformer installation DIMO Bring a

tasformer to that particular site and store there. Before we start the installation work customers request

us to come and check the conditions of the transformer. Because there is a sea near to the side. Then

we observed corrosion started in the new transformer. Therefore we decided to repaint the transformer

with the advice of the manufactures. For this purpose we went to the site in 05.12.2014 for repaint the

transformer.

2.4.3 SPI, Bathramulla

This is the new project of DIMO. It is building of ministry of defence. This project finished before I

joint the training. However we went to the site in 10.12.2014 for observe the current situation of the

site before handover to the customer. And prepare necessary documents for maintenance of the side by

the customer. Here DIMO used SIEMONS switchgears and TRAFRO Transformers.

2.4.4 Railway Crossing, Kosgama

This is the older project of DIMO. This is an automatic railway crossing signal control system. Here,

we observed that after the train passed the particular place the controller circuit was not reset and

remain the same stage continually. In my training period we tried many ways to solve the problem;

however we couldn’t fix the problem. Therefore we record a video the changes of the signals during

10

train passing the particular place and sent it to the manufacturing company for their advice and within

the period we did some temporary solutions for the railway crossing.

Fig.2.5 Railway Crossing Signal Controlling System, Kosgama

2.4.5 HSBC, Head Office

This is not a previous project of DIMO. However we were requested to investigate the blast occurred

in the switchgear and implements the system properly. Therefore we went to their office in 18.12.2014.

We get some advices from industrial consultants for this incident. We did insulation testing and thermo

graphical testing for identify the reason for the blast. Finally we identified the reason for the blast; that

is the ‘heat spot’ in the switchgear.

Fig.2.6 Blasted Switchgear in HSBC Head Office

11

2.4.6 Holsim, Puttalam

This is also a project of DIMO. It is one of the big projects as well. Here, we were requested to check

the temperature of the transformer because of the overheating observed by the customer. Therefore

DIMO discussed about this problem with the manufacture and senior engineers. Then we decided to go

there and plan to start the investigation from the oil test of the transformer. Therefore we went to

Holsim, Puttlam in 17.12.2014. And collected the oil sample and checked several tests. However we

couldn’t find any special dissolved gases from the oil sample. Then we analysis the problem with the

manufacture advise. Finally we identified that is not a saviour problem and it was occurred because of

Sri Lankan temperature change and the ventilation arrangement of the room where the transformer

installed. Therefore we advised to the customer to do proper ventilation arrangements for the place.

Fig.2.7 Collecting Oil Sample in Holsim-Puttalam

2.4.7 Iceland Resident

This is also one of the projects of DIMO. DIMO do necessary testing on the installed system annually.

Therefore we went to the site in 11.11.2014 for the transformer oil test. We checked all necessary tests

on the particular transformer and make sure that the transformer working perfectly.

Fig.2.8 Oil Testing on Transformer

12

CHAPTER 03- INSTRUMENTS

3.1 INTRODUCTION

DIMO (Pvt) Ltd provide high voltage and medium voltage installations. The projects can be classified

in to several categories according to the customer requirements. Such as Transformer project,

Generator project, Substation projects and Maintenance and Replacement projects. However there are

several instruments comes to the major role. Those are Transformer, Generator, Switchgear, Cables

and etc. In this chapter present several instruments which were used in the training period of me.

3.2 TRANSFOMERS

A transformer is an electrical device that transfers energy between two or more circuits through

electromagnetic induction. The working principal of the transformer is a varying current in the

transformer’s primary winding creates a varying magnetic flux in the core and a varying magnetic field

impinging on the secondary winding. The varying magnetic field at the secondary induces a varying

electromotive force (emf) or voltage in the secondary winding. We can select the transformer according

to our need. In my training period used transformers from two companies.

LTL Transformers – Sri Lanka

TRAFO ELETTRO – Italy

3.2.1 LTL Transformers

LTL is the transformer company in Sri Lanka. It is manufactured according to the international

standards. It is cheaper than other type of the transformer. DIMO choose the transformer for the project

with the requirement of the customer. The major advantage is select the LTL Transformer is if there

any problems in the transformer can easily solve with the help of the mother company. Performance

wise it has a good name in the industry. Here the sample of some LTL transformers.

Fig.3.1 LTL Transformers

13

In my training period DIMO used LTL transformer in two places. The basic detail of the transformer is

given below.

Table.3.1 Detail of the LTL Transformers

Basic Technical Features Unit Mobitel Site Navy Base

Capacity kVA 2000 400

Frequency Hz 50 50

No. of Phases 3 3

Primary Voltage V 11000 11000

Secondary Voltage V 415 415

Vector Symbol Dyn11 Dyn11

Temp Rise Winding

Top Oil

0C

0C

60

55

60

55

Method of Cooling ONAN ONAN

Impendence Voltage % 4.70 4.23

Excitation Current % 0.14 1.05

Standard IEC60076:2011 IEC60076:2011

Weight kg 6525 1625

3.2.2 TRAFO ELETTRO Transformers

TRAFO is a transformer company in Italy. DIMO uses this type of transformer from 2013. However it

performs well in the industry. But it is higher cost than LTL transformers. The major advantage is

there are two types transformers manufactured in this company. Those are given below.

Air insulated Transformer

Oil Insulated Transformer

14

In my training period I had the chance to work with only one kind of transformer. That is Air insulated

Cast-Resin transformer. The dry type transformers with HV windings cast in epoxy resigns under

vacuum have reached a high reliability due to the least technology progress. With these features, they

especially suitable for particular industrial applications: Foundries, Rolling mills, Refineries, Mines,

Offshore platforms, Tube railways and so on. The general characteristics are given below.

Reduced dimension

Humidity and adverse environment proof

Flame retardant & self-extinguishing

Almost no maintenance & environmentally safe

High short time overload capacity

Very low sound level

To be installed in the same room of circuit breakers

No necessity of low tank for oil

Possibility for forced air cooling to increase transformer capacity

Possibility to be assembled on side

High mechanical withstand capacity to resist power surges & short circuits

No special authorization for the transport

The basic detail of the transformer is given below.

Table.3.2 Detail of the TRAFO Transformers

Basic Technical Features Unit Galle Face Hotel RIL

Capacity kVA 1000 2000

Frequency Hz 50 50

Primary Voltage V 11000 11000

Secondary Voltage V 400 400

Vector Symbol Dyn11 Dyn11

Method of Cooling AN AN

Impendence Voltage % 5.9 7.4

Weight kg 3050 3850

15

3.3 SWITCHGEARS

In an electric power system, switchgear is the combinations of electrical disconnect

switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear

is used both to de-energize equipment to allow work to be done and to clear faults downstream. This

type of equipment is directly linked to the reliability of the electricity supply. One of the basic

functions of switchgear is protection, which is interruption of short-circuit and overload fault currents

while maintaining service to unaffected circuits. Switchgear also provides isolation of circuits from

power supplies. Switchgear is also used to enhance system availability by allowing more than one

source to feed a load. Switchgears can be classified into many categories. There are many insulation

medium can be used for switchgears. Such as Air, Oil, Gas (SF6), Hybrid, vacuum and Carbon dioxide

(CO2).

3.3.1 Benefits (General)

Saves lives

Peace of mind

Increases productivity

Saves money

3.3.2 Applications (General)

Power supply companies

Hotels

Shopping centres

Office buildings

Business centres

Water treatment plant

Metro Railways

Textile, paper and food

Industries

3.3.3 Vacuum Circuit-Breaker Switchgear (8BK88 PLUS)

In my training period DIMO used this type of switchgears according to the customer requirements.

This is medium voltage Switchgear. Normally it works up to 12 kV, and the insulation medium is air.

There are many safety roles included in the switchgear; isolation, secure against reclosing, verify safe

isolation from supply, Earth & Short circuit and Cover or barrier adjuster live parts. The technical

detail of the switchgear is given below in table 3.3

16

Table.3.3 Electrical data (maximum values) of 8BK88 PLUS

Ratings Rated Values (Max)

Rated voltage (frequency 50Hz) 12 kV

Rated current of feeders Upto1450 A

Rated current of the bus bar 2000 A

Rated power frequency withstand

voltage (rms) 1min.

28 kV**

Rated lightning impulse withstand

voltage (peak)

1.2/50 μs.

75 kV

Rated short circuit breaking current

(rms)

26.3 kA

Rated short time current (rms)

withstand (3 sec.)

26.3 kA

Rated short Circuit making current

(peak)

66 kA

Internal arc fault withstand capacity

(0.1 sec)

26.3 kA

Fig.3.2 Vacuum Circuit Backer Switchgear (8BK88 PLUS)

17

Fig.3.3 Compartments of 8BK88 PLUS

Fig.3.4 Circuit Breaker (Moveable)

To help ensure safe operation sequences of switchgear, trapped key interlocking provides predefined

scenarios of operation. For example, if only one of two sources of supply is permitted to be connected

at a given time, the interlock scheme may require that the first switch must be opened to release a key

that will allow closing the second switch. Complex schemes are possible. Normally customer selects

the suitable switchgear according to their protection requirement, cost, space of the site, sound level

etc.

18

CHAPTER 04- TECHNIQUES USED

4.1 INTRODUCTION

In my training period I had many experiences with installation of medium voltage power system.

Transformer, switchgear and high voltage cables are included in the installation. In those works

installation of earth system, cable termination, cable joint and unloading of instruments included.

Normally in most of the failures or damages in the power system occur due the mistakes in above

systems. Therefore DIMO do all necessary activities to succeed the maximum production of the system

and safety of the customer.

4.2 EARTH SYSTEM

In Electrical Engineering Ground or Earth is the reference point in an electrical circuit from which

voltage are measured, a common return path for electric current, or a direct physical connection to the

earth.

When talking about grounding, it is actually two different subjects: earth grounding and equipment

grounding. Earth grounding is an intentional connection from a circuit conductor, usually the neutral,

to a ground electrode placed in the earth. Equipment grounding ensures that operating equipment

within a structure is properly grounded. These two grounding systems are required to be kept separate

except for a connection between the two systems. This prevents differences in voltage potential from a

possible flashover from lightning strikes. The purpose of a ground besides the protection of people,

plants and equipment is to provide a safe path for the dissipation of fault currents, lightning strikes,

static discharges, EMI and RFI signals and interference. A safe grounding design has two main

objectives:

1. To carry the electric currents into earth under normal and fault conditions without exceeding

operating and equipment limits or adversely affecting continuity of service.

2. To ensure that the person in the vicinity of grounded facilities is not exposed to the danger of

electric shock.

There are four types of earth ground testing methods available.

Soil Resistivity (using stakes)

Fall-of-Potential (using stakes)

Selective (using 1 clamp and stakes)

Stakeless (using 2 clamps only)

19

4.2.1 Soil Resistivity

Soil Resistivity is the measure of how much the soil resists the flow of electricity. It is a critical factor

in design of systems that rely on passing current through the Earth’s surface. The soil resistivity value

is subject to great variation, due to moisture, temperature and chemical content. Typical Values are

Usual values: from 10 up to 1000 (Ω-m)

Exceptional Values: from 1 up to 10,000 (Ω-m)

Soil quality may vary greatly with depth and over a wide lateral area, estimation of soil resistivity

based on soil classification provide only a rough approximation. Actual resistivity measurements are

required to fully qualify the resistivity and its effects on the overall transmission system. Several

methods of resistivity measurement are frequently employed

4.2.1.1 Wenner method

Fig.4.1 Method of Connecting Equipment in Wenner Method

The Wenner four-pin method, as shown in Fig.4.1 above, is the most commonly used technique for soil

resistivity measurements. Using the Wenner method, the apparent soil resistivity value is given below.

Where,

ρE = measured apparent soil resistivity (Ωm)

a = electrode spacing (m)

b = depth of the electrodes (m)

RW = Wenner resistance

When measure as "V/I" as shown in Fig.4.1; If b is small compared to a, as is the case of probes

penetrating the ground only for a short distance (as normally happens), the previous equation can be

reduced like below.

20

4.2.1.2 Schlumberger method

Fig.4.2 Method of Connecting Equipment in Schlumberger Method

In the Schlumberger method the distance between the voltages probe is a and the distances from

voltages probe and currents probe are c .Using the Schlumberger method, if b is small compared

to a and c. and c>2a, the apparent soil resistivity value is:

Where,

ρE = measured apparent soil resistivity (Ωm)

a = electrode spacing (m)

b = depth of the electrodes (m)

c = electrode spacing (m)

RS = Schlumberger resistance

4.2.2 Fall-of-Potential

The Fall-of-Potential test method is used to measure the ability of an earth ground system or an

individual electrode to dissipate energy from a site.

Fig.4.3 Method of Connecting Equipment in Fall-of-Potential Test

21

4.2.3 Selective Measurement

Selective testing is very similar to the fall-of- Potential testing, providing all the same measurements,

but in a much safer and easier way. This is because with Selective testing, the earth electrode of

interest does not need to be disconnected from its connection to the site.

Fig.4.4 Method of Connecting Equipment in Selective Testing

4.2.4 Stakeless Measurement

The Stakeless measurement is about measure earth ground loop resistances for multi grounded systems

using only current clamps. This test technique eliminates the dangerous, and time consuming activity

of disconnecting parallel grounds, as well as the process of finding suitable locations for auxiliary

ground stakes. You can also perform earth ground tests in places you have not considered before:

inside buildings, on power pylons or anywhere you don’t have access to soil.

Fig.4.5 Test Current Paths in the Stakeless Method

22

4.3 CABLE TERMINATION

In all power projects cables comes to the biggest position. When connect the transformer and switchgear

to the system we need a protected and safe connection method of cables. In my training period when we

do the cable termination we followed instruction EPP 0277(I) -9/99 terminations for screened 3-core

polymeric insulated cable with armour 7.2 kV to 36 kV. Check the insulation level, condition of the cable

also an important part of cable termination. In high voltage applications small amount of dust may reduce

the level of insulation as well. Therefore have to clean the cable time to time in the termination also a

safety procedure. But it may different for other kind of cables. The procedure of the cable termination is

given below.

Fig.4.6 Procedure for Cable Termination

23

4.4 UNLOADING METHODS

Unloading of transformer and switchgear is an important think for a project. In my training period I

had experience about the unloading methods. There are several methods using for unlading. It is differ

for various instruments. When doing the unloading have to consider about the properties and

arrangement of the instrument inside the box and have to consider manufactures advices about the

device. Various kinds of unloading methods are given below. The lifetime of the instrument may

reduce because of the wrong unloading methods. It is a big responsible job of a project engineer.

Fig.4.7 Unloading of LTL Transformer

Fig.4.8 Unloading of TRAFO Cast-Resin Transformer

Fig.4.9 Unloading of SIMENS Switchgear

24

CHAPTER 05- STANDARDS AND TESTS

5.1 INTRODUCTION

In power system Standard and Tests are very important. In my training period I observed that all the

projects done by DIMO with the international standard. Normally after complete the project DIMO do

testing commissioning; and gives the report to the customer to check that for their satisfaction. DIMO

follows IEC standards and IEEE standards as well. However both of the standards are almost same.

Therefore in my training period all the measurements are taken with the maximum safety level. In all

transformer installation projects FAT is one of the important think for the manufacturing company,

customer and DIMO. More than these tests some other tests also precede by DIMO for maintenance

purposes and faulty identification.

5.2 TESTING & COMMISSIONING

Testing and commissioning is the last work in the project. The tests included in the test given

below.

5.2.1 HV Switchgear

Current (& Summation) Transformer

Insulation resistance test (with Insulation tester)

Winding resistance test (with Omicron CPC 100 primary injection kit)

Excitation Curve (with Omicron CPC 100 primary injection kit)

Burden test (with Omicron CPC 100 primary injection kit)

Ratio & Polarity test (with Omicron CPC 100 primary injection kit)

Voltage Transformer

Insulation Resistance test (with Insulation tester)

Ratio & Polarity test (with Omicron CPC 100 primary injection kit)

Burden test (with Omicron CPC 100 primary injection kit)

Bus bars and connections

Insulation resistance at 5kV DC (with Insulation tester)

Circuit Breaker

Static Contact Resistance test( with Omicron CPC 100 primary injection kit )

Insulation Resistance test ( 5 kV Insulation tester )

Protection relay

Overcurrent & Earth fault test (with Omicron CMC 356 secondary injection kit)

5.2.2 Power Cable

Insulation resistance test at 5 kV DC

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5.2.3 Power Transformer

Insulation resistance test at 5kV DC/1kV DC (with Insulation Resistance tester)

Winding resistance at central tapping and extremes (with Omicron CPC 100 primary injection

kit)

Turns ratio test at all tap positions (with Omicron CPC 100 primary injection kit)

Vector group test (with Omicron CMC 356 secondary injection kit and multi meter)

Magnetic Balance test ( with Omicron CPC 100 primary injection kit and multi meter)

Functional test of temperature control unit

5.3 FAT

The Factory Acceptance Test (FAT) is a major project milestone in an electrical installation project,

where the equipment and/or system integrator demonstrates that the system design & manufacturing

meets the contract or purchase Order specifications. Generally a substantial financial payment to the

vendor is triggered by a successful FAT; therefore the FAT must be conducted formally & be

witnessed by the system owner, with a formal record of discrepancies & non conformities & how they

are to be handled.

5.3.1 Major Requirements Include in the Contract for a FAT

The FAT must be witnessed by the system owner, project manager or designee.

The equipment should be fully pretest by the vendor before the witnessed FAT.

The FAT includes all equipment being supplied by the vendor.

The FAT procedure is to be presented to the system owner for approval at least two weeks

before the witnessed FAT, & should be derived from validation specifications as laid out in the

Functional Required Document.

5.3.2 Procedure of the FAT

Review the specification line by line while checking the equipment or drawings for compliance

with the specification, including any change orders.

Inspect for workmanship.

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Inspect for problems that can occur during installation or use the equipment, for example,

lifting points & safe access to components for maintenance, etc.

Test of the equipment per the vendor’s approved procedure; these should include functionality

testing & regulatory testing.

5.3.3 Tests included in FAT

Insulation Resistance Test

Voltage Ratio Test

DC Resistance Test

OIL Dielectric Strength Test

Separate Voltage Withstand Test

Induced Overvoltage Withstand Test

No Load Test

Full Load Test

Check of Phase Displacement

5.3 Transformer Oil Tests

Dissolved Gas-In-Oil Analysis

Insulation Overheating

Insulation Liquid Overheating

Corona

Arcing

Screen Testing

Dielectric Breakdown

Interfacial Tension

Color

Acidity

Power Factor

Water Content

PCB Tests

Metals-In-Oil

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CHAPTER 06- SERVICES OF DIMO

6.1 INTRODUCTION

DIMO (Pvt) Ltd provides many services to their customers. Therefore they can easily select what they

want. And DIMO provide warranty also to the customers after the installation.

6.2 HV PANEL

6.2.1 Breaker Operation Test

Breaker operation testing is one of the most important tests that can be used to test the circuit

breaker operation and to check the healthiness of the trip circuit. Following steps will take

during breaker operation testing.

Close Operation Test-Local-Remote

Trip (Trip Neutral Control)

Protection Trip

6.2.2 Functional Check

During functional testing we check for the healthiness of all the components involved in the

circuit breaker operation. Following tests will conduct in the Functional check.

Emergency Trip

Aux. Switch Operation

On- Off Indications (Lamp + Flag)

Trip/trip circuit healthy Lamp Indication

Limit Switch for spring charge motor

Test/Service Limit Switch

Operation Counter

6.2.3 General Servicing

Tight all mechanical & electrical connections to a standard torque

Cleaning of all contact points using relevant Chemical and applying contact grease

wherever required

Cleaning of all compartment inside the plants

Lubrication of all Moving Parts of the breaker Trolley

Testing of Insulation level (CB, CT,VT, Bus Bar)

Testing Circuit Breaker For the Operation

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6.3 TRANSFORMER SERVICE

Transformer is an aging asset, with the rising energy demand and the critical need to avoid

unplanned outages it is important to conduct routing monitoring of the transformers . There are

basically two options as mentioned below.

6.3.1 Transformer Testing

Turns ratio test

Winding resistance test

Insulation resistance test

Excitation test

6.3.2 Transformer General Maintenance

Cleaning the complete transformer and Tight all mechanical & electrical connections to a

standard torque.

Servicing of transformer Terminals using relevant Chemical wherever necessary

Check cables/nuts & bolts and other parts of the transformer physically

Testing for insulation levels of LV-HV, LV-E & HV-E

Testing for Earthing Resistance

Submitting a Condition & recommendation report for transformer after service & testing

Cleaning of the transformer yard

6.4 PROTECTION RELAY TESTING

After a relay is commissioned it’s important to carry out regular maintenance tests. Some of the

advantages of such testing can be stated as, it will pin point a defective relay before it fails to

act during a fault, relay coordination, its adaptability to latest power system as many feeders an

loads might have got added over the years after the relay was installed. Not every kind of relay

requires the same frequency of maintenance testing however it’s advised to have periodic

maintenance tests once every 6-12 months.

6.4.1 Standard Tests for Numerical Relays

Operational test/ trip test: - checks functionality of I/O logics with respect to design.

Alarm test: - checks the functioning of Alarm, which is to notify of the errors in the

internal circuit.

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6.4.2 Testing Principles

Primary injection: - High current is injected to primary side of the CT. Test carried out

covers CT, conductors, relays and sometimes circuit breakers as well. The relay unit to

be isolated from the power system. Usually this principal is used at commissioning and

also if the secondary of the CT is not accessible.

Secondary injection: - Relay is disconnected from the CT and the stepped down current

is directly injected to relay. Therefore no need the primary side of the CT to be

disconnected from the rest of the system.

6.5 THERMAL IMAGING

Thermography is a method of inspecting Electrical & Mechanical equipment by obtaining heat

distribution pictures. The inspection is based on the fact that most components in a system

increase in temperature when malfunctioning. While carrying out Thermographic inspection

faults are often identified by comparing heat patterns in similar components operating in similar

load. The increase in temperature in an electrical circuit could be due to loose connections or a

worn bearing in mechanical equipment. In case of terminations using close type terminals or for

terminations up to 6 sq mm in size running temperature above 45 deg. Centigrade at partial

loads , cell for inspection and necessary correction.

Fig.6.1 Thermo Graphic Images of Power System

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CHAPTER 7- CONCLUSIONS

The industrial training program at DIMO, One of the leading power service provider for Sri

Lanka was a great experience for me where I could have industrial training experience in

many aspects of power projects. Other than that, it was a great experience for me where I

could learn and practice ethics and social skills for an industrial environment and as well as I

could gain the insight to appreciate even the smallest, but honest , supportive and cooperative

contribution of the staff towards the success of a company and for a better working environment.

I was assigned to DIMO Power Solution for 10 weeks; I got a chance to have my training in a

well-planned way in DIMO at that period. I am very thankful to Mr. Darshna Subasinghe (General

Manager – Power Solution Division, DIMO (Pvt) Ltd), and Mr. Nalin De Silva (Project Manager,

DIMO (Pvt) Ltd) And I think it was better that I had the panel discussions at DIMO in my training

period after I being exposed to the field in some level because there I first tried to understand the

technologies and the system by own with the help of the staff and some introductory lectures from

the staff and then at the training centers I could confirm what I learned. It was actually motivated

me to learn things. I really appreciate all the staff members at DIMO who helped me to gain all

these experiences and the training Planning sect ion of DIMO for coordinating my training.

I think it would be great if Trainees could have more experience on the transformer installation, system

refurbishment, fault identification and other engineering sections so that they could be more

exposed to technologies and the challenges to be faced as engineers in the future.

Finally I would like to state that the training experience I had at DIMO organized by the Industrial

Training Unit of University of Peradeniya in collaboration with NAITA was up to my

expectations and it was a great experience for me which would definitely help me in my future

carrier.