Industrial Training Report-II-DIMO

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.

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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

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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

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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

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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

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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.

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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

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 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

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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

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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
 Manufacture of the transformer: - TRAFO ELETTRO (Italy)
 Type of the Transformer:- TES-R
 Voltage: - 11KV
Fig.2.2 Transformer and Switchgear of the Galle Face Hotel

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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.
 Manufacture of the transformer: - TRAFO ELETTRO (Italy)
 Type of the Transformer:- TES-R
 Voltage: - 11KV
Fig.2.3 Transformer and Switchgear of RIL Site

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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.
 Manufacture of the transformer: - LTL(Sri Lanka)
 Type of the Transformer:- Oil Immersed Transformer
 Voltage: - 11KV
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

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 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

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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

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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

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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

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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
0
C
0
C
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

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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

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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

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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)

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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.

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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)

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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.

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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

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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

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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

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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

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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

25
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.

26
 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

27
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

28
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.

29
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

30
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 section 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.

Industrial Training Report-II-DIMO

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