VISHWA INT (1).pdf

VISVESVARAYA TECHNOLOGICAL UNIVERSITY, BELAGAVI-590018, KARNATAKA
Internship Report On
“STUDY OF RELAY TESTING”
A report Submitted in partial fulfillment of requirements for the award of degree of
BACHELOR OF ENGINEERING IN
ELECTRICAL & ELECTRONICS ENGINEERING
Submitted By
NAME
VISWANATHA R
Internal Internship Guide
Under The Guidance of
USN
4SM19EE409
External Internship Guide
Dr. KUMARASWAMY B G M.E.,Ph.D., Mr.DEVARAJA B
Prof.,& Head. Dept., of E&E
S.J.M.I.T. Chitradurga.
220/66/11 KV,R T Sub Division
KPTCL Chitradurga
S.J.M INSTITUTE OF TECHNOLOGY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
(Affiliated to Visvesvaraya Technological University, Belagavi, Recognized by AICTE,
New Delhi and approved by Government of Karnataka)
2021-22

S J M Vidyapeetha ®
S.J.M INSTITUTE OF TECHNOLOGY, CHITRADURGA
(Affiliated to Visvesvaraya Technological University, Belagavi, Recognized by AICTE,
New Delhi and approved by Government of Karnataka)
P.B No.73,NH4 Bypass Road,Chitradurga-577502
NAAC Accredited with ‘B++’ Grade
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
CERTIFICATE
This is to Certify that the internship entitled “STUDY OF RELAY TESTING” is a benefited
word carried out by VISWANATHA R (4SM19EE409), studying in final year BE in Electrical
and Electronics Engineering at SJMIT, Chitradurga, during the year 2021-22 is a record of student’s
own work carried out under our guidance. It is certified that all suggestions indicated have been
incorporated in the report and one copy of it being submitted to the library. The internship report has
been approved as it satisfies the academic requirement in respect of internship work. If is further
understood that by this certificate the under signed do not endorse or approve any statement made,
opinion expressed or conclusion drawn there in but approve the internship only for the purpose for
which it is submitted.
…………………….………. ………......…………………… …………………………….
Signature of Co-ordinator Signature of the H.O.D Signature of the Principal
Mrs. Sushmita Deb Chaudhury M.Tech., Dr.Kumaraswamy.B.G M.E.,Ph..D Dr.P.B.Bharath M.Tech., Ph..D
Asst. Prof., Dept.,of E&E Prof.& H.O.D Dept of E&E Principal of S.J.M.I.T
External viva
Name of the Examiners Signature with date
1. .................................….. 1.…………………………
2. ……………………… 2….......................................

ACKNOWLEDGEMENT
I heartily express the deep sense of gratitude to his holiness Dr. Shivamurthy Murugha
Sharanaru, the President, SJM Vidyapeetha, Sri Bruhanmatha, Chitradurga, for providing us all the
facilities with blessings.
We remain indebted forever to all the Management Authorities of SJM Vidyapeetha®,
Chitradurga, for the encouragement and support in carrying out this internship successfully.
We would like to heartily thank Administrator, HRDC, KPTCL, and Bangalore for giving
us the opportunity to do an internship within the organization. It is indeed with a great sense of
pleasure and immense sense of gratitude, we would like to thank all the people of the organization who
worked along with us and created enthusiastic working environment.
We express sincere and heartfelt thanks to our External Internship guide Mr. Devaraja B.
Assistant Executive Engineer (Electrical), RT Sub division, KPTCL, Chitradurga, for his valuable
guidance, support and encouragement throughout in completing this internship successfully.
We extend our sincere and heartfelt thanks to Dr.P.B.Bharath M.Tech.,Ph.D. Principal, SJMIT,
Chitradurga, for providing us the right ambience and constant inspiration in carrying out this internship
successfully.
We heartily express our gratitude to Dr. Kumaraswamy.B.G M.E. Ph.D Head of the Department,
Electrical & Electronics Engineering, SJMIT, Chitradurga, for his encouragement and support in
carrying out this internship successfully.
We express sincere and heartfelt thanks to our internal internship guide
Mrs. Sushmita Deb Chaudhary M.Tech., Asst. Prof., Dept., of E & E SJMIT Chitradurga. in
completing this internship successfully.
We thank all the Teaching faculty, Non-teaching faculty, supporting staff of Electrical &
Electronics Engineering Department SJMIT, Chitradurga and all those who have helped us directly or
indirectly in completing this internship successfully.
INTERNSHIP ASSOCIATE
VISWANATHA R 4SM19EE409

CANDIDATE DECLARATION
I am VISWANATHA R (4SM19EE409), student of Electrical and Electronics Engineering at SJM
Institute of Technology, Chitradurga, hereby declare that we own full responsible for the information
provided in this work titled “STUDY OF RELAY TESTING” submitted to Visvesvaraya Technological
University and HRDC, KPTCL, Bangalore. To the best of our knowledge, this internship work has been
submitted in full to KPTCL for the award of certificate.
We have completely taken care in acknowledging the contribution of others in this academic work.
We further declare that in case of violation of intellectual property rights and particulars declared, found
at any stage, we, as the candidates will be solely responsible for the same
Date:
Place: Chitradurga
Name of the Students USN Signature
VISWANATHA R 4SM19EE409

ABSTRACT
The report an overview of 220 KV Substation. It includes electricity transmission and
distribution process at KPTCL Chitradurga substation. It is an assembly of apparatus which is
installed to transmission and distribution of electric power. It has an outdoor substation, different
equipment used in substations, lighting arrestors, isolators, current transformers etc. Transformers
which is being used here is shell type transformer for step down purpose. Different instruments
transformers voltage, current and CVT are also being used.
Protective relays and devices have been developed over 100 years ago to provide “last
line” of defense for the electrical systems. They are intended to quickly identify a fault and isolate
it so the balances of the system continue to run under normal conditions. The selection and
applications of protective relays and their associated schemes shall achieve reliability, security,
speed and properly coordinated. Mean while, protective devices have also gone through significant
advancements from the electro mechanical devices to the multifunctional, numerical devices of
present day. As the protected components of the electrical systems have changed in size,
configuration and their critical roles in the power system supply, some protection aspects need to
be revisited (i.e. the use of protection systems to reduce arc flash energy in distribution systems).
This presentation reviews the established principles and the advanced aspects of the selection and
application of protective relays in the overall protection system, multifunctional numerical devices
application for power distribution and industrial systems, and addresses some key concerns in
selecting, coordinating, setting and testing of smart relays and systems.

CONTENTS
Chapter No Title Page No
1 Introduction 1-1
2 Overview of 220/66/11KV SRS Chitradurga 2-2
3 Single Line Diagram of 220/66/11KV SRS Chitradurga 3-3
4
4.1
Brief description of equipment in Substation
Bus bars
4-18
4.2 Lightening Arresters
4.3 Capacitor Voltage Transformer
4.4 Wave Trap
4.5 Isolators (GOS)
4.6 Circuit Breakers
4.7 Instrument Transformers
4.8 Power Transformer
5
5.1
Relay & Protection
Types of Protective Relay
19-30
5.2 Transformer protection relay,
5.3 Earth-fault relay,
5.4 Overcurrent relay
5.5 Distance relay
6 Station Earthning 31-33
7 Maintenance of Substation 34-35
8 Fire Extinguisher 36-37
9 Experience & Outcomes of INTERNSHIP 38
10 Conclusion 39
11 Do’s and Don’ts 40-41

Study of Relay Testing Of Substation 2021-22
Dept. of E & E Engg, SJMIT, Chitradurga Page 1
CHAPTER 1
INTRODUCTION
Now days the electrical power demand is increasing very rapidly. For fulfilling
demand the various power generating stations are constructed. According to the constructional
principles, the generating stations are constructed. These generating stations are far away from
the load centers. It is delivered to consumer through a large network of transmission and
distribution. At many place in the line of power system, it may be desirable and necessary to
change some characteristics
Ex: voltage, frequency, power factor of electric supply.
For transmitting the generated power requires long and high voltage transmission
networks. Generally, the voltage in transmission is of higher order, thus SUBSTATION is
used. In substations, the voltage level is reduced to 66/11KV with the help of various
equipment.
For example: generating voltage i.e., of 11KV the power stepped up to the high
voltage 66KV then to 220KV for transmission of electric power. Similarly near the consumer
localities, the voltage may have stepped down to utilization level.

CHAPTER 2
Overview of 220/66/11KV SRS Chitradurga
220/66/11kv receiving station, Chitradurga
Main supply for this station is comes from 400kV station located at Guttur and from
400kV PGCIL Beeranahalli. Substation via 220kV station located at Thallak comprises of
five no. of power transformers, three are of 100MVA 220/66/11kV, other two transformer is
of 66/11kV 12.5MVA. Where in 220kV is step downed to 66kV using 100MVA
transformers. The 66 kV bus transmits power to 15 no’s of downstream 66/11kV Substations
viz.
1. Chitradurga
2. Pandrahally
3. H.D.pura
4. Chitrahalli
5. Holalkere
6. Hireguntanur
7. Sirigere
8. Bharamasagara
9. Madanayakanahally
10. Turuvanuru
11. Ramagiri
12. Balenahally
13. Aimangala

CHAPTER 3
Single Line Diagram of 220/66/11KV SRS Chitradurga
Figure: Schematic diagram of the 220kV RS, Chitradurga.
Guttur and Thalak are 220kV lines.
T1 and T2 are 100MVA transformers which are in parallel operation. T3 is 100MVA
transformer connected to 66kV bus 2.

CHAPTER 4
Brief Description of Equipment In Substation
4.1 BUS BARS
Bus bar is a system of electrical conductors in a generating or receiving station on which
power is concentrated for distribution. It is made up of a (copper, brass or aluminium) in the
form of a metallic strip or bar. The bus bar used in 220KV SRS is usually of Flexible ACSR
or aluminum stranded busbar supported by two ends by strain insulators.
In substation, it is often desired to disconnect a part of the system for general
maintenance and repairs. Isolators operate under no load condition. If any fault occurs
through it, then circuit breaker is tripped off and the faulty section of busbar is easily
disconnected from the circuit.
The two lines in the bus are separated by a small distance by a conductor having a connector
between them. This is so that one can work at a time and other works only if the first is
having any fault.
In SRS 220/66/11KV substation aluminum buses are used due to its low cost and have
ability to withstand high mechanical strength and higher level of conductivity. Two busbars
used in both 220KV and 66KV power line.
There are two types of Bus bars:
• Main bus bar: It is connected with relays and a number of measuring instruments.
• Auxiliary bus bar: It is connected with equipment’s and the switches used for connecting
feeders.
The following are the important bus bars arrangements used at substations:
• Single bus bar system
• Double bus bar system

Study on Relay Testing Of Substation 2021-22
Maintenance of Bus bar
• Check the tightness of the wire connections, which is connected to the circuit breakers.
• Clean the bus bar and switchboard area with the help of vacuum cleaner.
4.2 Lightning Arresters
Lightning Arrester is
Figure:4.1 BUS BAR
a device designed to protect electrical equipment from high
transient voltage surges. They are the most effective means of protecting an electrical
apparatus against traveling voltage waves caused by lightning and switching. So, these
are placed in beginning of the substation.
Operation:
• It works on the principle of non-linear resistance.
• The Zno inside the LA connects the corner ring with the ground. In normal voltage
behaves like an insulator, when surge strike Zno melts down and creates a
conductive path.
Types of Arresters
1. Rod gap arrester
2. Horn gap arrester
3. Multi gap arrester
4. Expulsion type LA
5. Valve type LA

Specifications:
Substation
rated
voltage
220kv 66kv 11kv
Lighting
arrester
rating
198-216kv 60kv 9kv
Where Found:
LA is found in all phase line of each feeder
circuit and also, it is at inlet and outlet of Main
Transformer.
If protection fails lightning arrester
introduces thousands of kilovolts that may damage
the transmission line.
Surge Counter:
Surge counter will automatically record
Number of lightning and switching surge discharges
of station class surge arresters on five digital
cyclometer dials. It is mounted at the base of
lightning arrester.
Lightning arresters discharge current passes through
a shunt arrangement to charge a capacitor, discharge
of this capacitor through solenoid operates the
cyclometer count.
Fig:4.2 Lightning arrester
4.3 Capacitor Voltage Transformer
A capacitor voltage transformer (CVT) is a transformer used in power systems to step-
down extra voltage high voltage signals and provide low voltage signals either for
measurements or to operate a protective relay.

These are high pass filters (carrier frequency 50Hz to 500Hz) pass carrier frequency to
carrier panels and power frequency parameters to switch yard. In its most basic form, the
device consists of three parts: two capacitors across which the voltage signal is split, an
inductive element used to tune the device and a transformer used to isolate and further step-
down the voltage.
Fig:4.3 Capacitor voltage transformer
In practice the first capacitor C1, is often replaced by a stack of capacitors connected
in series. This results in a large voltage drop across the stack of capacitors, that replaced the
first capacitor and a comparatively small voltage drop across the second capacitor C2, and
hence the secondary terminals.
CVT’s are primarily used for voltage measurement, providing voltage signals to
metering units, protection relay devices, and automatic control devices. CVT’s are typically
single-phase devices used for measuring voltages in excess of 100KV
voltage transformers would be uneconomical.
where the use of
4.4. WAVE TRAP
Wave trap is an instrument using for trapping of the wave. It is also called as Line
trap. It is connected in series with the power line. It blocks the high frequency carrier waves
(24KHz to 500KHz) and let power waves (50Hz to 60Hz) to pass through.
It helps in trapping the high frequency communication signals on the line from the
substation and diverting them to the telecom / tele protection panel in the substation control

room through coupling capacitor.
Wave trap is used to create high impedance to the carrier wave high frequency
communication entering in to unwanted destinations typically substation. Carrier wave
communication uses up to 150 kHz to 800 kHz frequency to send the all the communication.
This is relevant in Power Line Carrier Communication (PLCC) systems for
communication among various substations without dependence on the telecom company
network.
Design:
• Wave Trap is placed at the beginning of substation
• It consists of inductor coil in series with power line
• Wave traps are in cylindrical shape.
• It consists of main coil, tuning device and protective device
• Main coil: it is outer part of the Wave Trap
• It is made from Standard aluminum cable
• Tuning and protective device mounted inside the main coil
Uses:
• To prevent the transmission of high frequency carrier signal of power line
Communication to unwanted destination.
• It acts as a barrier for filter to prevent signal losses.
• To attenuate the shunting effects of high voltage lines.
=
Fig:4.4 Wave Trap

4.5. Isolators (GOS)
An Electrical Isolator is a manually operated mechanical switch that capable of
opening or closing a circuit meant for repair from a healthy section in order to avoid
occurrence of more fault. Hence it is also called as disconnector. Isolator does not have any
system to avoided arching during disconnection. Because isolators work when it is in no-load
condition or small amount of load is present and it is dangerous to operate in full load
condition.
There are different types of isolators such as single-break isolator, double-break isolator,
pantograph isolator, bus isolator, line isolator, etc.
In SRS, both single or centre-break and double break isolators are used. The isolator
consists three stacks of post insulator and having two contacts that is male and female
contacts. The male contact is a moving contact and female contact is spring-loaded figure
contact. If the contacts isolate at the centres then it is Centre break isolator and if the
contacts are isolated at both ends of the isolator then it is a Double break isolator.
The standard values for rated duration of short time current capacity to withstand for
isolator and earthing switch is normally 1 second. A value of 3 seconds is also sometimes
specified. For 33KV, horizontal type isolating switches are used. The rated normal current is
630A at 36KV. For 11KV, both horizontal and vertical mounting isolating switches of 400A
at 12KV are used.
Opening operation:
In the beginning, open the major circuit breaker.
Then divide or separate the load from a system with isolator opening.
Close the earth switch. Earth switch can become with an interlock system with isolator.
That’s means when isolator is open only that time earth isolator will be closed.
Closing operation:
Detach the earth switch.
Shut the isolator.
Shut the circuit breaker.

Isolator maintenance:
• Checking of the male/female contacts for good condition and proper
connections.
• Checking proper alignment of male & female contacts & rectify if required.
• Lubrication of all moving parts on regular basis.
• Tightness of all earthing connections.
• In case of isolators with earth switch, check electrical and mechanical interlock i.e.,
isolator can be closed only when earthing switch is in open condition and vice versa.
Voltage class: 220KV, 66KV, 11KV
Make: GR Power Gear and HVELM Industries
Fig:4.5 Vertical swing single/Centre Break Isolator & Horizontal swing double break isolator

4.6. Circuit Breaker
Circuit Breaker is a manually operating or by remote control electrical switch designed to
protect an electrical circuit from damage caused by overload or short circuit. When a high current
or voltage is interrupted, an arc is generated. The length of the arc is proportional to the voltage
while the intensity (or heat) is proportional to the current.
Circuit Breaker contains both fixed contacts and moving contacts. When a fault occurs on
any part of the system, the trip coils of the breaker get energized and the moving contacts are
pulled apart by some mechanism, thus opening the circuit.
Classification of circuit breaker:
• Oil Circuit Breaker
• Air Circuit Breaker
• SF6 Circuit Breaker
• Vacuum Circuit Breaker
Operating mechanism used for the operation of breaker:
 Spring: Both for closing and tripping operations.
 Pneumatic: compressed air pressure for both closing and tripping operations.
 Semi-pneumatic: Closing of breaker by spring and tripping by pneumatic.
 Hydraulic: Compressed hydraulic oil pressure for both closing and tripping.
 Presently, oil and air circuit breakers are outdated at SRS DVG substation.SF6 and
vacuum circuit breakers are used.
SF6 CIRCUIT BREAKER
A circuit breaker in which sulphur hexafluoride (SF6) gas is used as the arc quenching
medium known as SF6 circuit breaker. These circuit breakers are available for the voltage ranges
from 33KV to 800KV and even more.
Working of SF6 Circuit Breaker:
In the closed position of the breaker, the contacts remain surrounded by SF6 gas at a pressure
of about 6.0 bars. When the breaker operates, the moving contact is pulled apart and arc is struck
between the contacts. The movement of the moving contact is synchronized with the opening of a
value. The value permits SF6 gas pressure from the reservoir to the arc interruption chamber. High
pressure flow of SF6 gas rapidly absorbs the free electrons in the arc path. It forms immobile

negative ions which are ineffective as charge carriers. The result of that medium between the
contacts quickly builds high dielectric strength and causes the extinction of the arc. After the
breaker operation (i.e., arc extinction), the value is closed by the action of set of springs.
Properties of SF6 gas:
• Very high dielectric strength.
• Low decomposition by arcing.
• High thermal and chemical inertia.
• Superior arc extinguishing capacity.
Name plate details of SF6 CB fig:4.6 SF6 Circuit Breaker
VACUUM CIRCUIT BREAKER
A circuit breaker in which vacuum is used as the arc quenching medium, known as vacuum
circuit breaker. They are employed for 11KV outdoor applications with limited rate of 100MVA.
The switching on and closing operation of current carrying contacts and an arc interruption takes
place in a vacuum chamber in the circuit breaker which is called Vacuum Interrupter.
Working of Vacuum Circuit Breaker:
When the contacts of the breaker are opened in the vacuum, an arc is produced between the
contacts by the ionization of metal vapours of contacts. The arc is quickly extinguished because
the metal vapours, electrons and ions produced during arc are diffused in a short time. The arc
extinction in a vacuum breaker occurs with a short contact separation (0.625cm) because of very

fast rate of recovery of dielectric strength.
Properties of Vacuum Circuit Breaker:
• High insulating strength.
• They do not need periodic refilling of oil or gas.
• Rapid recovery of high dielectric strength.
Fig:4.6.1 Vacuum Circuit Breaker
Maintenance of circuit breaker:
• Tightness of power connections & control wiring connections.
• Checking of contact resistance, close open timing, insulation resistance.
• Checking of air pressure for pneumatic operated breaker (leakages if any).
• Checking of gas pressure for SF6 circuit breaker (leakages if any).
• Checking of controls, interlocks & protections like checking of pole discrepancy system i.e.
whether all the three poles are getting ON-OFF at the same time.
• Cleaning of auxiliary switches by CTC or CRC spray and checking its operation.
4.7. INSTRUMENT TRANSFORMERS
Instrument Transformers are defined as the instruments in which the secondary current or
voltage is substantially proportional to the primary current or voltage and differs in phase from it
by an angle which is approximately zero for an appropriate direction of connection.
The line in sub-station operates at high voltage and carries current of thousands of amperes.
The measuring instruments and protective devices are designed for low voltage (generally 110v)
and current (about 5A). Therefore, they will not work satisfactory if mounted directly on the

power lines. This difficulty is overcome by using Instrument Transformers, on the power lines.
There are two types of instrument transformer:
 Current Transformer
 Voltage Transformer
4.7.1. Current Transformer
Current transformers are used to obtain reduced current from the power systems for the
purpose of measurements, control and protection.
➢ Current transformers are used for both metering and protection purposes.
➢ Depending upon the type of protections adopted, number of secondary cores required
will be decided.
➢ All 11kV feeders require 2 core CTs for metering and protection.
➢ All 11 kV Banks, 66kV lines and 110kV lines and 11033-11kV and 6611kV power
transformers requires 3 core CTs for metering, Primary protection (Distance
protection for lines and Differential protection for Transformers) and Backup
protection (Over Current and Earth fault protection).
➢ 220kV class CTs are of 5 cores for metering, Primary protection (Distance
protection), Backup protection (Over Current and Earth fault protection) and 2 cores
for Bus bar protection (Main and Check zones).
➢ 400kV class CTs are of 5 cores for metering, Primary protection (Main-I Distance
protection), Backup protection (Main-II Distance protection only) and 2 cores for
Bus bar protection (Main and Check zones).
➢ Accuracy Class of each secondary core differs depending upon the type of
protection.
➢ If the type of protection is same then the class of such cores will be same.
➢ While ordering the accuracy class, VA burden, Instrument safety factor (ISF-for
metering core), Accuracy limiting factor (ALF for backup protection core) and knee
point voltage, Excitation current and Rct for primary protection cores will be
specified.

• Specifications of HVCT:
Type : 08KF-245
Frequency : 50HZ
HSV/NSV : 245/220 Kv
Insulation Level : 460/150 Kv
Oil Weight : 160 kg
Total Weight : 720kg
Ith : 40 kA/1sec
Idyn : 1000 kAp
Fig:4.7.1 Name plate of Current transformer
CT Polarity:
The polarity of CT is determined by the direction in which the coils are wound around the core
of CT (clockwise or anti clockwise) and by which way the secondary leads are brought out of the
transformer case.
• The primary of the CT is always marked as P1 and P2.
• The CT shall be mounted such that the primary current always flows from ‘P1 to P2’.
Maintenance of Current transformer (CT):
• Checking of oil level& leakage, rectify the same immediately.

• Checking of insulation resistance.
• Power connection tightness.
• Secondary connection tightness.
• Cleaning and bushings/insulators.
• Check the proper earthing of body connection.
• Check the earthing of CT secondary core star points.
• Check the working and stainless steel bellows.
• Check the nitrogen pressure in case of nitrogen filled CT.
4.7.2 Potential Transformer (PT)
Potential Transformer is a type of instrument transformer which is used to step down the
voltage to a safe value so that this low voltage can be used for low rating relays & meters.
Construction: It consist of a primary winding and
secondary winding. The primary winding has large
number of turns & secondary winding has much less
turns depending on the secondary out voltage. Standard
secondary output voltage is 110V or 400V etc. while
primary voltage may be much higher like 11KV or
33KV etc.
Working principle: It works on the principle of
transformer; It is just like a small step-down
transformer which reduces voltage in secondary
winding. It is connected parallel in electrical circuit.
Fig:4.7.2 Potential transformer
Burden of PT: Burden of PT is the total VA load on
secondary winding of PT.

Advantages of PTs:
1. PTs help in reducing the cost of electrical system as by installing it in the system so that low
voltage metering/protection equipment could be used.
2. It improves the safety of a person working as he has to deal with low voltage equipment.
Application of PTs:
1. It is used for synchronizing of generators and metering purposes.
2. It is used for protection of circuits/feeders/impedance of generators.
3. It is used for synchronizing of generators.
Types of PTs:
• According to phases, VTs are of two types – 1) Single Phase & 2) Three Phase
• According to design – Electromagnetic type, Capacitor type & Optical type.
Maintenance of Potential transformer (PT):
• Checking of insulation resistance.
• Check the proper earthing of body connection.
• Check the secondary fuse condition & replace if required by proper ratings.
• Cleaning of bushings/insulators.
• Power connection tightness.
• Secondary connection tightness.
• Check the working of stainless-steel bellows.
4.8 Power Transformer
It is a static device, use to step up or step down ac voltages and to transfer electrical power from
one voltage level to another. Tap changers are used for voltage control. Usually transformers for
outdoor use are oil filled. For large capacity, three single phase units are used to form a three
phase bank.
Transformer is used to boost voltage levels so as to decrease line losses during transmission.

Accessories for Power Transformer
3 ph, 50Hz, Core type 3 winding Star/Star/Delta transformer vector
group:YNynOd11,OLTC(on-load tap changer),bushing CT for tertiary of
ratio:1000/1A,5P20,15VA,ONAN,ONAF/OFAF with fan control cubicle, Numerical RTCC
(Remote tap changing control)panel with optic fibre temperature sensor, oil etc. complete with
2*50% separate radiator bank on left side and terminal connector suitable for Moose ACSR on
primary and double Drake ACSR secondary side of transformer and Neutral connectors suitable
for 02Nos of 75mm x 10mm copper flats 100MVA, 220/66/11KV.

CHAPTER 5
Introduction to Protective Relays
Protective relays work in concert with sensing and controlling devices to accomplish their
function. Under normal power system operation, a protective relay remains idle and serves no active
function. But when fault or undesirable condition arrives Relay must be operated and function
correctly.
A power system consists of various electrical components like Generator, transformer,
transmission lines, isolators, circuit breakers, bus bars, cables, relays, instruments transformers,
distribution feeders and various types of loads. Faults may occur in any part of power system as a
short circuit and earth fault. Fault may be single line to ground, double line to ground, line to line,
three phase short circuit etc. This results in flow of heavy fault current through the system. Fault
level also depends on the fault impedance which depends on the location of fault referred from the
source side. To calculate level at various points in power system, fault is necessary.
The protection system operates and isolates the faulty section. The operation of the protection
system should be fast and selective i.e., it should isolate only the faulty section in the shortest
possible time causing minimum disturbance to the system. Also, if main protection fails to operate,
there should be a backup protection for which proper relay co-ordination is necessary. Failure of a
protective relay can result devastating equipment damage and prolonged downtime.
Definition: The relay is the device that opens or closes the contacts to cause the operation of the
other electric control. It detects the intolerable or undesirable condition with an assigned area and
gives the commands to the circuit breaker to disconnect the affected area. Thus protects the system
from damage.
Functions of Protective Relay
These are the main functions of protective relay:
1. To sound an alarm or to close the trip circuit of a circuit breaker so as to disconnect Faulty
Section.
2. To disconnect the abnormally operating part so as to prevent subsequent faults. For e.g.
Overload protection of a machine not only protects the machine but also prevents Insulation
failure.
3. To isolate or disconnect faulted circuits or equipment quickly from the remainder of the
system so the system can continue to function and to minimize the damage to the faulty part.
For example – If machine is disconnected immediately after a winding fault, only a few coils

may need replacement. But if the fault is sustained, the entire winding may get damaged and
machine may be beyond repairs.
4. To localize the effect of fault by disconnecting the faulty part from healthy part, causing least
disturbance to the healthy system.
5. To disconnect the faulty part quickly so as to improve system stability, service continuity and
system performance. Transient stability can be improved by means of improved protective relaying.
6. To minimize hazards to personnel
Working Principle of Protective Scheme
Protective relaying senses the abnormal condition in a part of power system and gives an alarm or
isolates that part from healthy system. Protective relaying is a team work of CT, PT, protective relays, time
delay relays, trip circuits, circuit breakers etc.
Protective relaying plays an important role in minimizing the faults and also in minimizing the damage
in the event of faults.
Basic connections of circuit breaker control for the opening operation. Figure above shows
basic connections of circuit breaker control for the opening operation. The protected circuit X
is shown by dashed line. When a fault occurs in the protected circuit the relay connected to CT
and PT actuates and closes its contacts.
Current flows from battery in the trip circuit. As the trip coil of circuit breaker is

energized, the circuit breaker operating mechanism is actuated and it operates for the
opening operation.
Desirable Qualities of Protective Relaying
1. Selectivity,
2. Discrimination
3. Stability
4. Sensitivity,
5. Power consumption
6. System Security
7. Reliability
8. Adequateness
9. Speed & Time
Types of Relays
Types of protection relays are mainly:
A. Based on Characteristic:
1. Definite time Relays.
2. Inverse definite minimum time Relays (IDMT)
3. Instantaneous Relays
4. IDMT with Instantaneous.
5. Stepped Characteristic
6. Programmed Switches
7. Voltage restraint over current relay
B. Based on logic:
1. Differential
2. Unbalance
3. Neutral Displacement
4. Directional
5. Restricted Earth Fault
6. Over Fluxing

Dept. of E & E Engg, SJMIT, Chitradurga Page22
7. Distance Schemes
8. Bus bar Protection
9. Reverse Power Relays
10. Loss of excitation
11. Negative Phase Sequence Relays etc.
C. Based on actuating parameter:
1. Current Relays
2. Voltage Relays
3. Frequency Relays
4. Power Relays etc.
D. Based on Operation Mechanism:
1. Electro Magnetic Relay
2. Static Relay
➢ Analog Relay
➢ Digital Relay
➢ Numerical / Microprocessor Relay
3. Mechanical relay
➢ Thermal
➢ OT Trip (Oil Temperature Trip)
➢ WT Trip (Winding Temperature Trip)
• Bearing Temp Trip etc.
➢ Float Type
➢ Buchholz
➢ OSR (oil surge relay)
➢ PVR (pressure valve relay)
• Water level Controls etc.
➢ Pressure Switches

➢ Mechanical Interlocks
➢ Pole discrepancy Relay
E. Based on Applications
1. Primary Relays
2. Backup Relays
Types of Relay based on Relay Operation Mechanism
1. Electromagnetic Relay
Electromagnetic relays are further categorized under two following categories.
1.1 Electromagnetic Attraction Relay
This Relay works on Electromagnetic Attraction Principle
1.2 Electromagnetic Induction Relay
This Relay works on Electromagnetic Induction Principle
2. Solid State (Static) Relay
Solid-state (and static) relays are further categorized under following designations:
2.1 Analog Relay
In Analog relays are measured quantities are converted into lower voltage but similar
signals, which are then combined or compared directly to reference values in level
detectors to produce the desired output.
2.2 Digital Relay
In Digital relays measured ac quantities are manipulated in analogue form and
subsequently converted into square-wave (binary) voltages. Logic circuits or
microprocessors compare the phase relationships of the square waves to make a trip
decision.
2.3 Numerical Relay
In Numerical relays measured ac quantities are sequentially sampled and converted
into numeric data form. A microprocessor performs mathematical and/or logical
operations on the data to make trip decisions.
Purpose of Protection
The purpose of the protection is to detect electrical faults and abnormal conditions. It is
made to protect human beings and properties around the electrical network and that for
the protection must be fast and sensitive. Operation must be selective to minimize

power outages. Protection needs to be reliable and simple and must cover fully the
protected network.
Purpose of Controlling the Electrical Network
The purpose to control the electrical network is to be able to perform maintenance,
tests, development, troubleshooting and to minimize power outages from the
customers. The control of the electrical network is done by circuit breakers and
disconnectors that can cut-off the power from the line. A breaker is used to cut-off high
currents while a disconnector is used to make a clear separation between the
disconnected points of the line to ensure safety. Breakers and disconnectors need a
controlling unit, such as a protection relay that orders them to close or open. This
controlling unit takes orders from e.g. the SCADA operator but can also operate by
itself by means of protection.
The ABB line differential relay has the following protection and supervision functions:
➢ Stabilized differential low stage,
➢ Instantaneous differential high stage,
➢ Over current stage for overload protection,
➢ Over current stage for backup protection,
➢ Directional and non-directional earth fault protection,
➢ Auto-reclosing,
➢ Current circuit supervision and
➢ Protection communication supervision
Most commonly used relay types are as follows in substation
1. Transformer protection relay,
2. Earth-fault relay,
3. Overcurrent relay,
4. Distance relay,

1. Transformer Protection Relay
Generally Differential protection is provided in the electrical power transformer rated more
than 5MVA.
The Differential Protection of Transformer has many advantages over other schemes of
protection.
1. The faults occur in the transformer inside the insulating oil can be detected by
Buchholz relay. But if any fault occurs in the transformer but not in oil then it cannot be
detected by Buchholz relay. Any flash over at the bushings are not adequately covered by
Buchholz relay. Differential relays can detect such type of faults. Moreover Buchholz
relay is provided in transformer for detecting any internal fault in the transformer but
Differential Protection scheme detects the same in faster way.
2. The differential relays normally response to those faults which occur inside the
differential protection zone of transformer.
Differential Protection Scheme in a Power Transformer
Principle of Differential Protection
Principle of Differential Protection scheme is one simple conceptual technique. The
differential relay actually compares between primary current and secondary current of power
transformer, if any unbalance found in between primary and secondary currents the relay will
actuate and inter trip both the primary and secondary circuit breaker of the transformer.
Suppose you have one transformer which has primary rated current Ip and secondary current Is.
If you install CT of ratio Ip / 1A at the primary side and similarly, CT of ratio Is/1A at the
secondary side of the transformer. The secondaries of these both CTs are connected together in
such a manner that secondary currents of both CTs will oppose each other.
In other words, the secondary’s of both CTs should be connected to the same current coil
of a differential relay in such an opposite manner that there will be no resultant current in that
coil in a normal working condition of the transformer. But if any major fault occurs inside the
transformer due to which the normal ratio of the transformer disturbed then the secondary
current of both transformers will not remain the same and one resultant current will flow
through the current coil of the differential relay, which will actuate the relay and inter trip both
the primary and secondary circuit breakers. To correct phase shift of current because of star-
delta connection of transformer winding in the case of three-phase transformer, the current

transformer secondaries should be connected in delta and star as shown here.
At maximum through fault current, the spill output produced by the small percentage
unbalance may be substantial. Therefore, differential protection of transformer should be
provided with a proportional bias of an amount which exceeds in effect the maximum ratio
deviation.
2. Earth-fault relay
Restricted Earth Fault Protection of Transformer
An external fault in the star side will result in current flowing in the line current
transformer of the affected phase and at the same time a balancing current flows in the
neutral current transformer, hence the resultant current in the relay is therefore zero. So
this REF relay will not be actuated for external earth fault. But during an internal fault, the
neutral current transformer only carries the unbalance fault current and operation of
Restricted Earth Fault Relay takes place. This scheme of restricted earth fault
protection is very sensitive for internal earth fault of electrical power transformer. The
protection scheme is comparatively cheaper than differential protection scheme.
Restricted earth fault protection is provided in electrical power transformer for
sensing internal earth fault of the transformer. In this scheme, the CT secondary of each
phase of an electrical power transformer are connected together as shown in the figure.
Then common terminals are connected to the secondary of a Neutral Current Transformer
or NCT.
The CT or Current Transformer connected to the neutral of a power transformer is called

Neutral Current Transformer or Neutral CT or simply NCT. Whenever there is an
unbalancing in between three phases of the power transformer, a resultant unbalance current
flow through the closed path connected to the common terminals of the CT secondary’s. An
unbalance current will also flow through the neutral of the power transformer and hence there
will be a secondary current in Neutral CT because of this unbalance neutral current.
In Restricted Earth Fault scheme the common terminals of phase CTs are connected to the
secondary of Neutral CT in such a manner that secondary unbalance current of phase CTs,
and the secondary current of Neutral CT will oppose each other. If these both currents are
equal in amplitude there will not be any resultant current circulates through the said closed
path. The Restricted Earth Fault Relay is connected in this closed path. Hence the relay will
not respond even there is an unbalancing in-phase current of the power transformer.
3. Overcurrent Relay
Definition: The overcurrent relay is defined as the relay, which operates only when
the value of the current is greater than the relay setting time. It protects the equipment of
the power system from the fault current.
Depending on the time of operation the overcurrent relay is categorized into following
types.
 Instantaneous Overcurrent relay
 Inverse time Overcurrent Relay
 Definite Time Overcurrent Relay
 Inverse Definite Time Overcurrent Relay

 Very Inverse Definite Time Overcurrent Relay
 Extremely Inverse Definite Time Overcurrent Relay
 Instantaneous Overcurrent relay
Instantaneous Overcurrent Relay
The relay has no intentional time delay for operation. The contacts of the relay are closed
instantly when the current inside the relay rises beyond the operational value. The time
interval between the instant pick-up value and the closing contacts of the relay is very less.
The most significant advantage of the instantaneous relay is that it has low operating time.
It starts operating instantly when the value of current is more than the relay setting. This
relay operates only when the impedance between the source and the relay is less than that
provided in the section.
The most important feature of the relay is their speed of operation. The relay protects the
system from earth fault and also used for protecting the
system from circulating current. The instantaneous
overcurrent relay is placed in the outgoing feeder.
Inverse-Time Overcurrent Relay
The relay operates only when the magnitude of their
operating current is inversely proportional to the
magnitude of the energize quantities. The operating
time of relay decreases with the increases in the current.
The operation of the relay depends on the magnitude of
the current
The characteristic curve for the relay is shown in the figure below. The relay will not
operate when the value of current is less than the pick value. The relay is used for the
protection of the distribution lines. The inverse time relay is of three types.
Inverse Definite Minimum Time Relay
The relay whose operating time is approximately proportional to the fault current is
known as the IDMT relay. The operating time of the relay is maintained by adjusting the
time delay setting. The IDMT relay uses the electromagnetic core because it can easily
saturate for the current having larger magnitude than pick up current. The relay is used for
the protection of the distribution line.

Very Inverse Relay
The inverse characteristic of the relay is more than the IDMT. Such type of relay is
used in the feeder and on long transmission lines. The relay is used in the places where there
the magnitude of the short-circuit current fall rapidly because of the large distance from the
source. It is used for sensing the fault current which is free from the fault location.
Extremely Inverse Relay
The characteristic time of the relay is extremely large as compared to the IDMT and
the Very inverse relay. This relay is used for protecting the cable, transformer, etc. The relay
can operate instantly when the pickup value of the current is more than the relay setting time.
The relay provides faster operation even under the fault current. It is used for sensing the
overheating of the machines.
The inverse time relay is used in the distribution networks and the power plants. The
relay gives the fast operation in the fault conditions because of their fault time characteristic.
4. Distance Protection Relay
Distance protection relay is the name given to the protection, whose action depends on
the distance of the feeding point to the fault. The time of operation of such protection is a
function of the ratio of voltage and current, i.e., impedance. This impedance between the
relay and the fault depends on the electrical distance between them. The principal type of
distance relays is impedance relays, reactance relays, and the reactance relays.
Distance protection relay principle differs from other forms of protection because their
performance does not depend on the magnitude of the current or voltage in the protective
circuit but it depends on the ratio of these two quantities. It is a double actuating quantity
relay with one of their coil is energized by voltage and the other coil is energized by the
current. The current element produces a positive or pick-up torque while the voltages element
has caused a negative and reset torque.
The relay operates only when the ratio of voltage and current falls below a set value.
During the fault the magnitude of current increases and the voltage at the fault point
decreases. The ratio of the current and voltage is measured at the point of the current and
potential transformer. The voltage at potential transformer region depends on the distance
between the PT and the fault.
If the fault is nearer, measured voltage is lesser, and if the fault is farther, measured
voltage is more. Hence, assuming constant fault impedance each value of the ratio of voltage

and current measured from relay location comparable to the distance between the relaying
point and fault point along the line. Hence such protection is called the distance protection or
impedance protection.
Distance zone is non-unit protection, i.e., the protection zone is not exact. The distance
protection is high-speed protection and is simply to apply. It can be employed as a primary as
well as backup protection. It is very commonly used in the protection of transmission lines.

CHAPTER 6
STATION EARTHING
Concept of earthing:
The electrical earthing is done by connecting the non-current carrying part of the equipment
or neutral od supply system to ground. Mostly, the galvanised iron is used for the earthing. The
earthing provides the simple path to the leakage current. The short circuit current of the
equipment passes to the earth which has zero potential. Thus, protects the system and equipment
from damage.
For outdoor substation, a main earthing ring should be provided round the substation
which should be connected to all earth electrodes. The ring should be laid so as to have shortest
connection from transformers, circuit breakers etc.
Importance of earthing:
• The earthing protects the personnel from the short circuit current.
• The earthing provides the easiest path to the flow of short-circuit current even after the
failure of the insulation.
• The earthing protects the apparatus and personnel from the high voltage surges and lightning
discharge.
• The earthing ensures that the ground potential rise of the substation does not have any
dangerous effects on the nearby communication stations.
➢ Earth mat: Earth mat is made by joining the number of rods through copper conductors
copper conductors. It reduced the overall grounding resistance. It is mostly used in a placed
where the large fault current is to be experienced.
Fig:6 Earthing pit fig:6.1 Earth mat Layout

Types of earthing: Earthing can be divided into Neutral earthing and Equipment earthing
Neutral Earthing: It deals with the earthing of the system neutral to ensure system security and
protection that the neutral points are held at earth potential and return path is available to neutral
current.
Points to be earthed: Transformer neutral is to be earthed to two separate and distinct earth
electrodes interconnected with substation earth mat.
Equipment Earthing: It deals with earthing of non-current carrying parts of equipment’s to
ensure safety to personnel and protection against lightning. Points to be earthed: All non-current
carrying metallic parts of equipments, structures, enclosures, overhead shielding wires, flanges
of bushings, cores of transformer, cable sheaths, pipes etc.
JELLY SPREADING:
Spreading of baby granite jelly of 20/25 mm size of thickness of 100mm over the area of the
substation is extremely useful in controlling the step and touch potential in addition to the
following advantages.
• It avoids the movement of reptiles.
• It hampers the growth of weeds in the station yard.
• It drastically reduces the escape of moisture from the soil, the presence of which keeps the
resistivity of the soil low.
Advantages of Jelly spreading:
• Provides high resistivity surface layer (Prime objective)
• Impediment to the movement of reptiles.
• Prevents formation of oil pool from leaked oil.
• Discourages growth of weeds.
• Helps in retaining moisture in the under-laying soil.
• Discourages running of person in the switch yard.
Step Potential: Step potential is the potential difference between the feet of a person standing
on the floor of the substation, with 0.5 m spacing between the one step, during the flow of fault
current through the ground system.

Estep = (RB + 2RF) IB
Where,
Rb- Body resistance,
Rf- Foot resistance,
Ib- Current passing the body.
Touch Potential: Touch potential is the potential difference between the fingers of a raising
hand touching the faulted structure and the feet of the person standing on substation floor.
The person should not get a shock even if the ground structure is carrying fault current,
i.e., the touch potential should be very small. Hence touch potential and step potential should
be below 45V, so that a person walking on substation floor does not get shock to high step
potential.
Step Potential Touch Potential

CHAPTER 7
MAINTENANCE OF SUBSTATION
Substation maintenance is a key part of any plant’s maintenance program. Failures in key
components such as racking mechanisms, meters, relays and buses are the most common cause
of unplanned outages. Transmission, distribution and switching substations generally have
switching, protection and control equipment and one or more transformers. By having proper
maintenance, the station equipment’s can be safeguarded so that the equipment will give its
maximum efficiency and reliable operation.
Maintenance may be defined as the upkeep of the substation electrical equipment in proper
working and efficient condition to derive the following:
1. Reliable and efficient operation
2. Optimum utilization
3. Availability
4. Reduced down time
5. Detection of premature faults
6. Minimizing revenue loss etc.
The maintenance schedule of an SRS substation is as follows:
• The batteries in the battery room are daily inspected for their specific gravity that should lie
in between 1180-1220 and each cell should carry a voltage in between 1.8-2.2V, the float
voltage must be 2.25 +0.02V.
• The SF6 gas pressure will be inspected by the staff and in which lower gas pressure will be
noted down out of 3 limbs. This pressure limit should be around 6 bar rel.
• The transformer winding and oil temperature readings of 3 phases are taken down. If the
temperature is beyond the rated value then the transformer load will be reduced by load
scheduling.

General maintenance:
• Checking of DC emergency lamps in control room.
• Tightening of cable connections, cleaning of bus bars, panels, vermin proof of cable entry in
DC panels.
• Painting of transformers, Breakers, structures etc. once in 5 years.
• Inspection / Overhauling of OLTC in transformers 25,000 operations or 2 years, whichever is
earlier, with oil replaced or as recommended by the transformer supplier.
• Replacing of Fire extinguisher after every usage or if not operated, once in a year.
• Painting of name plates, phase indicators, Bay indicators and earth electrodes.
• Inspection of outdoor yard for any Arcing / oil leakages.
• Cleaning of C & R panels, AC panels, DC panels and battery charger.
• Earth resistance testing of all equipment’s especially of transformer neutral, LAs, etc.

CHAPTER 8
FIRE EXTINGUISHER:
“Fire is a rapid, self-sustaining oxidation process accompanied by the evolution of heat and
light of varying intensity”. Fire results from the combination of fuel, heat and oxygen when a
substance is heated to a certain critical temperature called the “Ignition Temperature”. The material
will ignite and continue to burn as long as there is fuel, the power temperature and a supply of
oxygen (air).
➢ Classification Fires is mentioned below:
Class A Fires: There are files involving solid materials (such as wood, cloth, paper, rubber, etc),
normally of an organic nature (compounds of carbon), in which combustion generally occurs with
the formation of glowing ambers, where the cooling effect of water is essential for extinguishment of
fire.
Class B Fires: These are fires involving flammable liquids e.g., kerosene, naphtha, LDO, mix oil,
gasoline, where blanketing effect (A layer of foam over the surface of burning liquid) is essential for
extinguishing fire.
Class C Fires: These are fires involving gases e.g. LPG, Methane, Ethylene, Propylene, Hydrogen
etc. Fire can be put out either by dry chemical powder or carbon dioxide gas. Here isolation of
leaking source is essential.
Class D Fires: These are fires involving combustible metals, such as magnesium, titanium, sodium.
These fires can be put out with the help of special dry powders. Ordinary DCP of Foam or Water is
of no use on such fires.
Electrical Fires: According to latest concept, electrical fires do not constitute a particular class. Any
fire involving electrical equipment is a fire of class A, or class B. The normal procedure in such fires
is to cut-off the electrical supply of the equipment and to use an extinguishing media appropriate to
the burning material. Water in the form of hose stream should in no case be used in electrical fires
unless positive isolation of hose stream should in no case be used electrical fires unless positive
isolation of electric supply has been ensured.

Caution:
1. Do not use Foam Fire Extinguishing on fires involving live
electrical equipment and metal.
2. Do not use CO2 Fire Extinguisher on big size fire. It is also to
be used on mental fire. While extinguishing oil precaution
against flash black or resignation is to be taken.
not
fire,

CHAPTER 9
EXPERIENCE AND OUTCOMES OF INTERNSHIP
15 days of Internship made us enthusiastic experience. It’s about time for a reflection
on our internship. This experience has influenced our future and how our university educating
prior to our internship has helped me here.
First and foremost this experience has affected us in many ways. As with most
experiences in life things do not usually go as planned, but always end up leaving you with
something good and worth-while (and often better than what you had anticipated).
At first we were slightly frustrated and disappointed that the mandate and it was very
difficult to get internship in most of the companies as they ask for work experience or they
want us to work for the whole year but our internship duration framed by the university was
of 4 weeks and we contacted the Assistant Executive Engineer of 220kV RS Chitradurga
Mr. Devaraja B. He was very co-operative and Sir gave us an opportunity to do the
internship in 220/66/11kV SRS.
In the first week they explained the substation equipment and we were allowed to see
the yard and observe and in the next week they explained the duties of the shift engineers and
the hierarchy of the KPTCL for the next 2 weeks they made us help the shift engineers in
taking readings and help them in load management etc.
The time we spent in 220kV SRS Chitradurga as an intern for 4 weeks was a
memorable one. For us it was rich in experience sharing and helped us to discover our
potential.
Though, still have to learn, this INTERNSHIP helped much on our future career

STUDY OF RELAY TESTING OF SUBSTATION 2020-21
CHAPTER 10
CONCLUSION
Now from this internship we can conclude that electricity plays an important role in our
life. We are made aware of how the transmission of electricity is done. Transmission and
distribution stations exist at various scales throughout a power system. In general, they
represent an interface between different levels or sections of the power system, with the
capability to switch or reconfigure the connections among various transmission and distribution
lines.
➢ In this study, Overview and vital statistics of SRS, SLD of SRS, and description of main
components of substation has been studied briefly.
➢ The study of panel section (control room), protection scheme and battery room are studied
in detail with the help of relevant circuits.
➢ Importance of power transformers in the field of substations, name plate details and also
about ratings are focused which helps to increase the technical knowledge about the power
transformer.
➢ Maintenance of substation according to hourly, daily, monthly, yearly maintenance and
peak load of the station are studied with the help of lively taking records as well as
previous year records.
➢ And also noticed the control relay panel and metering details as well as taking readings.
Main advantage of KPTCL is maintaining transmission loss below 4% i.e., 3.82%.

Do’s and Don’ts
Do's
1) Do check for continuity of DC supply for efficient operation.
2) Do check for physical healthiness of battery cells and their connections.
3) Do ensure or and satisfy for electrolyte level in cells if level is low, fill with distilled
water.
4) Do ensure for proper operations of battery charger and satisfy with regard to DC fuses
etc.
5) Do check frequently for tripping and closing of equipment through relays and switches.
6) Do check and provide efficient ground connections to all DC equipments and provide
if possible earth leakage relays for efficient DC supply.
7) Do check for proper earthing connections for equipments like LAs, PTs, Transformers,
Circuit breakers and CTs etc.
8) Do check for smooth and easy operations of circuit breakers and GOS etc.
9) Do check the following during the shut downs and record their values. Meggering of
LAs, Power Transformers, Circuit breakers, UG Cables, CTs, PTs, Earth Mat and
Earth electrodes.
10) Do check all the equipments during shut down for dust etc., from both inside and
outside as the case may be.
11) Do provide proper illumination in the ODS yard and controlroom.
12) Do keep fire fighting device intact and ready to use inposition.
13) Do keep a vigil on over voltage and over loading of equipments like Power
Transformers, CTs, and PTs etc.
14) Do ensure that all the contacts on bus bar, OCB, CTs, PTs, Battery charger, Panel
boards and Tap changer are OK.
15) Do keep Circuit breakers open whenever DC supplyfailure is observed till.
16) Do check to see that all fuses are intact with proper ratings.
17) Do check for working condition for proper operation of motors and other equipments
with provision of safety device such as single phase inverter, over load protectionetc.

Don'ts
1) Do not open any GOS on load without opening Circuit breaker.
2) Do not close any GOS before opening the concerned circuit breaker.
3) Do not open GOS before tripping the concerned CBs for issuing L/C on 11 KV
feeder / line / transformer / capacitor.
4) Do not operate breakers when air and gas pressure is below operatingvalue.
5) Do not operate GOS and circuit breakers manually without wearing safety glovesetc.
6) Do not close earthing GOS unless respective CB and GOS are open and authorities
requiring LCs require so and the line is de-energized and ensure no back feeding on
the line.
7) Do not keep Power Transformer in charged conditions during abnormal records of
winding and oil temperature.
8) Do not charge any Power transformer without being satisfied with respect to neutral
connection being perfectly earthed with two numbers of minimum separate earth
connections.
9) Do not allow specific gravity of lead acid cells to below 1200(+/- 5%) and cell voltage
below 1.8 volts per cell.
10) Do not allow workmen to attend any work without line clear and with the equipment
being perfectly earthed and if necessary with discharging the equipments (such as
LAs, Capacitor, UG Cables etc) duly taking precaution that safety devices areused.
11) Do not issue LC on EHV lines without obtaining NFBC from the other end.
12) Do not keep any CTs in charge conditions without its secondary’s in closed circuit or
short circuited.
13) Do not use bare fingers or hands to determine whether a circuit islive.

PHOTOGRAPHY:
Our team with our Guide-Mr. Devaraja.B, Assistant Executive Engineer (Electrical), KPTCL Chitradurga.

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