GOVERNMENT POLYTECHNIC ADITYAPUR

IN-PLANT TRAINING REPORT

“ELECTRICAL TRANSMISSION FROM SUB-STATION”

JHARKHAND URJA SANCHARN NIGAM LIMITED

132/33 kV GRID SUB-STATION , GOLMURI

ANKIT RAY (22402080008)

5th semester, Diploma (2022-2025)
Department of Electrical Engineering
Government Polytechnic, Adityapur

under the guidance of…

Mr. Binod Kumar Sharma
JUSNL, Training officer, Golmuri)
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CERTIFICATE

This is to certify that Mr. ANKIT RAY of Government

Polytechnic Adityapur, 3rd year Branch Electrical
Engineering Reg. No. 2240208008 have attended In-
Plant Training of “Electrical Transmission From
Sub-Station” from 132/33 kV Grid Sub-station ,
Golmuri for the period from 26 August 2024 to 30
September 2024 during training period , his work was
satisfactory and this report was submitted under my
guidance .

Mr. Binod Kumar Sharma Prof. Ashwini Kumar

Tra Training officer, JUSNL Golmuri) (Assistant Dean)
School Of Engineering & IT
Jam. Jamshedpur, 831004

Dr. Kashinath Jena DATE:

Assistant Professor PLACE: JAMSHEDPUR
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ACKNOWLEDGEMENT

I would like to express my heartfelt gratitude to all those who have contributed
to the successful completion of my in-plant training at JUSNL, focusing on the
project “Electricity transmission and distribution processes at JUSNL.” First
and foremost, I express my deepest appreciation to Mr. BINOD SHARMA sir,
my mentor and guide, for their unwavering support, invaluable guidance, and
continuous encouragement throughout this training period. Their expertise,
patience, and willingness to share knowledge have been instrumental in
enriching my learning experience. I would like to extend my thanks to all the
technicians and engineers at Transmission Grid who generously shared their
insights, expertise, and experiences with me. Their willingness to impart
knowledge and answer my queries have been invaluable in broadening my
understanding of different equipment’s used in substations, Bus-bar, surge
arrestor, isolator, Earth switches, Current Transformer, etc. I am indebted to my
professors and instructors at GOVT. POLYTECHNIC ADITYAPUR or
equipping me with the foundational knowledge and skills that laid the
groundwork for my training. Their teachings have been instrumental in shaping
my academic and professional journey. In conclusion, I am deeply grateful to
everyone who has played a part, however big or small, in shaping my learning
and growth during this in-grid training experience. Your contributions have been
invaluable, and truly appreciative of the opportunity to learn and grow in such a
dynamic and enriching environment.

Thank You!
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ANKIT
RAY
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DECLARATION

I sincerely declare that :

1. I am the sole writer of this report.

2. The details of Training and experience

contain in this report describe my involvement
as a trainee in the field of ELECTRICAL
ENGINEERING

3. All the information Contain in this report is

certain and correct to the knowledge.

Signature __________________
Name:- ANKIT RAY
Registration no – 22402080008
Date -
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About The Organization

Jharkhand Urja Sancharan Nigam Limited (JUSNL) was formed in January,

2014 as a wholly owned subsidiary of the Jharkhand Urja Vikas Nigam
Limited, Ranchi, registered under the Companies Act, 1956.

After enactment of Electricity Act, 2003, it was mandated to unbundle the State
Electricity Boards as it is prohibited SEBs to function as integrated power
utilities. It envisaged a separate and coordinated functions of the Generation,
Transmission and Distribution functions of the State. In compliance of the
provisions of the Act, the erstwhile JSEB has been unbundled and vide
Jharkhand State Electricity Reforms Transfer Scheme, 2013; the assets,
liabilities, rights and obligations have been transferred to the following
successor companies:
Jharkhand Urja Vikas Nigam Limited (JUVNL) the Holding Company to
coordinate the functions assigned to subsidiary companies)

 1.Jharkhand Urja Utpadan Nigam Limited (JUUNL) (Subsidiary

Company taken over the Generation function (GenCo.) of the erstwhile
JSEB)

 2.Jharkhand Urja Sancharan Nigam Limited (JUSNL) (Subsidiary

Company taken over the Transmission (TransCo.) function of the
erstwhile JSEB)

 3. Jharkhand Bijli Vitaran Nigam Limited (JBVNL) (Subsidiary

Company taken over the Distribution (DisCom) function of the erstwhile
JSEB).
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Contents

1.Introduction Page No.

1.1 Topography of Golmuri

1.2 Importance of Electrical Energy
1.3 Selection of site
1.4 Safety Practices in Transmission
1.5 Introduction of 132/33 kV Grid
1.6 Single Line Diagram of Substation

2. Important Parts of Substaion

2.1 Insulator
2.2 circuit breaker
2.3 Instrument Transformer (C.T , P.T )
2.4 Surge Arrester
2.5 CVT
2.6 Wave Trap

3. Power Transformer
3.1 Parts of Power Transformer

4. Important part of transformer

4.1 Buchholz relay

4.2 Differential protection
4.3 Conservator
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4.4 Breather
4.5 Oil Temperature Indicator
4.6 Winding temperature indicator

5. Important Part Of Transmission Line

5.1 Earthing
5.2 Tower
5.3 Control and Relay Room
5.4 Battery Room
5.5 Protective Relay
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1. Introduction
Energy is the basic necessity for the economic development of a country. Many functions
necessary to present-day living trend to halt when the supply of energy stops. They
availability huge amount of energy in the modern times has resulted in the modern times
has resulted in a shorter working day, higher agriculture and industrial production , a
healthier and more balanced diet and better transportation facilities. As a matter of fact,
there is a closer relationship between the energy used per person and his standard of
living.
Energy exists in different form in the nature but the most important form is the
electrical energy. The modern society is so much dependent upon the use of electrical
energy that it has become a part and parcel of our life.

1.1 TOPOGRAPHY OF GOLMURI

Golmuri is part of Jamshedpur in the East Singhbhum district of Jharkhand, India. The
topography of Golmuri is a blend of flat and slightly undulating terrain, typical of urban
areas developed on the Chotanagpur Plateau. Here are the detailed aspects:

1. Elevation: Golmuri has an average elevation of 159 meters (522 feet) above sea level.
Being part of the plateau region, it sits at a relatively higher altitude compared to
nearby plains but is not as elevated as the surrounding hillier regions.

2. Latitude and Longitude:

Latitude: Approximately 22.8005° N
Longitude: Approximately 86.2356° E
These coordinates place Golmuri in the northeastern part of Jamshedpur.

3.Surrounding Topography: The region around Golmuri is generally flat due to urban
development, but it is surrounded by more hilly areas typical of the larger Chotanagpur
Plateau.
The presence of the nearby Subarnarekha and Kharkai rivers influences the drainage
patterns and supports the local ecosystem, though Golmuri itself does not have major
water bodies within it.
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In summary, Golmuri’s topography reflects a moderately elevated, urbanized area

with a mix of flat and slightly undulating terrain, in line with its location on the edge of
the Chotanagpur Plateau.

1.2 IMPORTANCE OF ELECTICAL ENERGY

We need energy like various form like heat, light. sound. etc. The development
new technology made it possible to covert electrical energy into any form of
energy. This time electrical energy an important position in all over the world. The
running of modern industrial structure depends on the low cost and the
uninterrupted supply of electricity. Electrical energy is considered to be superior
over other energy forms the following facts gives the proof for it.

1) CONVENIENT ENERGY FORM: Electrical energy could be converted form

one form into any other form. As for example we know that a bulb glow when
electricity passes through it. It means conversion of electrical energy into light
then a wire gets heated when current passes through It for a long time. Similarly,
electrical energy can be converted into any desired energy.

2) EASY TO CONTROL: The machine or devices which work on electrical

energy can easily be controlled i.e., an electrical motor could be switch on, off and
speed regulation with in a very easy manner where as a mechanical engine needs
much energy to get started.

3) FLEXIBILITY: - Flexibility is very easy to carry electricity from one place to

other by using the help of conductors

4) CHEAPNESS: - Electrical energy is much cheaper compared to other form of

energy.

The cost of production and availability is much larger compared to other form of
energy.

5) CLEANLINESS Electrical energy is not associated with polluting factors such

as smoke, dust, fumes, poisonous gases etc. the healthy atmosphere to each and all
living organism in the world.

6) HIGH EFFICIENCY TRANSMISSION: - The transmission efficiency of

electrical energy is much higher, is much higher usually the consumers are not
populated where the electricity is produced so it becomes necessary to transmits
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electrical energy to that part and this could do by mean of very long conductors
named transmission lines.

1.3 SELECTION OF SITE

Main points to be considered while selecting the site for Grid Sub-
Station are as follows:

I. The site chosen should be as near to the load centre as possible.

II. It should be easily approachable by road or rail for transportation of

equipment's.

III. Land should be fairly levelled to minimize development cost.

IV.Source of water should be as near to the site as possible. This is because water is

required for various construction activities (especially civil works), earthing and
for drinking purposes etc.

V. The sub-station site should be as near to the town/city but should be clear of

public places, aerodromes, and Military/police Installations.

VI. The land should be having sufficient ground area to accommodate substation

equipment, buildings, staff quarters, space for storage of material, such as store
yards and store sheds etc. with roads and space for future expansion.

VII. Set back distances from various roads such as National Highways, State

highway should be observed as per the regulations in force.

VIII. While selecting the land for the Substation preference to be given to the

Govt. land over private land.

IX. The land should not have water logging problem.

X. Far away from obstructions, to permit easy and safe approach /termination of

high voltage overhead transmission lines.

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1.4 SAFETY PRACTICIES IN TRANSMISSION SECTOR

"Safety' as a whole may be interpreted as the proper planning of work,

proper usage of safety tools, adopting safety procedures and exercise of
good Judgement and intelligent supervision.

Experience speaks, majority of the accidents occurred previously

because of :-

1) Over confidence
Negligence which could have been prevented by adhering to Safety
2)
Rules and Safety Practices
3)Avoidance of accidents require the whole hearted co-operation of all
employees of the organization. Generally, capable and mentally alert
employees avoid accidents.
4)Unsafe employee is a liability to the organization He is a danger to
himself, his fellow workers, his family, the public and the Corporation.
5)Accident due to: Carelessness, over confidence and inattentiveness
during the working period at the work site.
6) Non-adherence of the safety rules.
7) Non-usage of proper safety gadgets for the specific work
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1.6 SINGLE LINE DIAGRAM OF SUBSSTATION

 INSULATOR
The insulator serves two purpose. They support the conductor (or bus bar) and confine the
current to the conductor. T The most commonly used material for the manufactures of
insulators is porcelain.
There are 5 types of insulators used in transmission lines as overhead insulation:

• Pin Insulator
• Suspension Insulator
• Strain Insulator

• Shackle Insulator
• Stay Insulator

Pin, Suspension, and Strain insulators are used in medium to high voltage systems. While
Stay and Shackle Insulators are mainly used in low voltage applications.
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IMPORTANT PART OF SUBSTATION

 2.1 INSULATOR
The insulator serves two purpose. They support the conductor (or
bus bar) and confine the current to the conductor. T The most
commonly used material for the manufactures of insulators is
porcelain.

There are 5 types of insulators used in transmission lines as

overhead insulation:

• Pin Insulator
• Suspension Insulator
• Strain Insulator
• Shackle Insulator
• Stay Insulator

Pin, Suspension, and Strain insulators are used in medium to high

voltage systems. While Stay and Shackle Insulators are mainly used
in low voltage applications.
PYROMETALLURGY HYDROMETALLURGY ELECTROMETALLURGY

Extractive metallurgy is a process within metallurgical engineering that

focuses on the extraction of metals from their natural mineral deposits. It
involves a series of processes that convert raw ores into pure metals.
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1. Pin type insulator:

Pin Insulator is earliest developed overhead Insulator but still
popularly used in power network up to 33 KV system. Pin
type insulator can be one part, two parts or three parts type,
depending upon application voltage. In 11 KV system we
generally use one-part type insulator where whole pin.
Insulator is one piece of properly shaped porcelain or glass.
As the leakage path of insulator is through its surface, it is
desirable in Increase the vertical length of the insulator
surface area for Lengthening leakage path.
Post Insulator: Post insulators are similar to Pin insulators, but
post insulators are more suitable for higher voltage
applications.
Post insulators have a higher number of petticoats and a
greater height compared to pin insulators. We can mount this
type of insulator on supporting structure horizontally as well
as vertically. The insulator is made of one piece of porcelain
and it has clamp arrangement are in both top and bottom
end for fixing.
Suspension type insulator:
In higher voltage, beyond 33KV, it becomes uneconomical IGAM
to use pin insulator because size, weight of the insulator become
more handling and replacing bigger size single unit insulator are
quite difficult task. For overcoming these difficulties, suspension
insulator was developed.
In suspension insulator numbers of insulators are connected in
series to form a string and the line conductor is carried by the
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bottom most insulator. Each insulator of a suspension string is

called disc insulator because of their disc like shape.

2. Strain Type Insulator:

When suspension string is used to sustain extraordinary
tensile load of conductor it is referred as string insulator.
When there is a dead end d or there is a sharp corner in
transmission line, the line has to sustain a great tensile load
of conductor or strain. A strain insulator must have
considerable mechanical strength as well as the necessary
electrical Insulating properties.

3. Shackle Type Insulator:

The shackle insulator (also known as a spool insulator) is
usually used in low voltage distribution network. It can be
used in both the horizontal or vertical positions. The use of
such insulator has decreased recently after increasing the
using of underground cable for distribution purpose. The
tapered hole of the spool insulator distributes the load more
evenly and minimizes the possibility of breakage when
heavily loaded.

4. Stay Insulator:
For low voltage lines, the stays are to be Insulated from
ground at a height. The insulator used in the stay wire is
called as the stay insulator and is usually of porcelain and is
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so designed that in case of breakage of the insulator the guy-

wire will not fall to the ground.

2.2 CIRCUIT BREAKER:

A circuit breaker is an equipment, which can open or close a

circuit under normal as well as fault condition. These circuit
breaker breaks for a fault which can damage other
instrument in the station. It is so designed that it can be
operated manually (or by remote control) under normal
conditions and automatically under fault condition. There are
mainly two types of circuit breakers used for any substations.
They are (a) SF6 circuit breakers; (b) spring circuit breakers.

The use of SF6 circuit breaker is mainly in the substations

which are having high input, say above 220kv and more. The
gas is put inside the circuit breaker by force le, under high
pressure When if the gas gets decreases there is a motor
connected to the circuit breaker. The motor starts operating if
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the gas went lower than 20.8 bar. There is a meter connected
to the breaker so that it can be manually seen if the gas goes
low. The circuit breaker uses the SF6 gas to reduce the torque
produce in it due to any fault in the line.

2.3 INSTRUMENT TRANSFORMERS

The line in Sub-Station operate at high voltage and carry current of
thousands of amperes: The measuring instrument 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 installing
Instrument transformer, on the power lines. There are two types of
instrument transformer.

1. CURRENT TRANSFORMER

A current transformer is essentially a step-down transformer which steps-

down the current in a known ratio, the primary of this transformer consists of
one or more turn of thick wire connected in series with the line, the secondary
consists of thick wire connected in series with line having large number of
turns of fine wire and provides for measuring instrument, and relay a current
which is a constant faction Current transformers are basically used to take the
readings of the currents entering the substation. This transformer steps down
the current from 800 amps to l amp. This is done because we have no
instrument for measuring of such a large current. The main use of his
transformer is (a) distance protection; (b) backup protection; (c) measurement .
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2. POTENTIAL TRANSFORMER

It is essentially a step-down transformer and step down the

voltage in known ratio. The primary of these transformer
consists of a large number of turns of fine wire connected
across the line. The secondary way consists of a few turns
and provides for measuring instruments and relay a voltage
which is known fraction of the line voltage.
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2.4 SURGE ARRESTOR

Firstly we can see surge or lightening arresters. These lightening

arrestor can resist or ground the lightening if falls on the incoming
feeders. The lightening arrestors can work in an angle of 30 degrees
around them. They are mostly used for protection of the instruments
used in the substation. As the cost of the instrument in the station
are very high to protect them from high voltage from lightening these
lightening arrestors are used. It is a device used on electrical
power systems to protect the insulation on the system from the
damaging effect of lightning. Metal oxide varistors (MOVs) have been
used for power system protection since the mid-1970s. The typical
lightning arrester also known as surge arrester has a high voltage
terminal and a ground terminal. When a lightning surge or switching
surge travels down the power system to the arrester, the current
from the surge is diverted around the protected insulation in most
cases to earth.
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2.5 CVT

A capacitor voltage transformer (CVT) is a transformer used in power

systems to step-down extra high voltage signals and provide low
voltage signals either for measurement or to operate a protective
relay. 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 to the supply frequency and a
transformer used to isolate and further step-down the voltage for the
instrumentation or protective relay. The device has at least four
terminals, a high-voltage terminal for connection to the high voltage
signal, a ground terminal and at least one set of secondary terminals
for connection to the instrumentation or protective relay. CVTs are
typically single phase devices used for measuring voltages in excess
of one hundred kilovolts where the use of voltage transformers
would be uneconomical. In practical 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.
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 2.6 Wave Trap :

Wave trap is installed in a substation for
trapping the high frequency for
communication signal sent on the line from
remote substation and diverting them into
the telecom panel in substation control room.
Wave trap is also known as line trap. It is a
cylindrical shape device that is installed on
high voltage transmission power line to
prevent high frequency signal from being
transmitted to unwanted destination. It is
used in substation for PLCC(Power Line
Carrier Communication) which is a way to
transmit high frequency signal over power
transmission line for telecommunication,
telemonitoring and teleoperation.
It 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 150kHz to 800kHz frequency to send
the all the communication. These high
frequency damages the power system
components which are designed to operate
50 or 60 Hz. It consists of an inductor coil
which is connected in series with the high
voltage power system.
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POWER TRANSFORMER

Power transformer is the most important equipment of the

substation, because by this equipment power is transferred from
one level to another level. High voltage power transformer of large
KVA require more elaborate attention to insulation and to provision
for cooling than in necessary smaller distribution transformer. They
differ further in that power transformer are designed to have
considering greater leakage reactance than is permissible in
distribution transformer. In power transformer Inherent voltage
regulation is less important than the current limiting effect of
relatively high leakage impedance. There are total 3 Transformers
working with parallel operation in Golmuri substation and each of
rating 50 MVA.
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PARTS OF POWER TRANSFORMER

1. Main tank
2. Radiator
3. Conservator
4. Cooling fan
5. Breather
6. Winding
7. WTI/OTI
8. High and low voltage bushing
9. Tap changer
10. Core
11. Drain valve
12. Insulation
13. Drain vent
14. Explosion vent
15. Transformer oil
16. Buchholz relay
17. Gauges

1.Main tank:
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The main tank of a transformer

is a container that holds,
protects, and cools the
transformer's core and
windings. It also serves as a
reservoir for the transformer oil
and supports other
accessories.

2. Conservator:

It is the large cylinder by a pipe to the transformer. The transformer oil

is filled up to certain level in conservator. Remaining upper portion is
filled with air conservator oil is in communication with tank oil.
Expansion and contraction of transformer tank oil is accommodated by
the conservator. Direct contact with external air is avoided.

3. Cooling fans:
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Transformer cooling fans are used to

prevent overheating in power
transformers, which can lead to a
complete system failure. The operating
temperature of a transformer has a
significant impact on its service life,
and even short-term temperature
peaks can be critical.

4.Breather:

It is installed in a pipe from conservator. One end connected to air in

conservator. Other end connected to external air, Air cushion in the
upper portion of conservation is n communication with external
atmosphere through the breather. Breather is filled with silica gel
(pink). When oil in conservator rises air is let out through breather.
When oil is contracted during loads low temperature air is breathed in
by the moisture and admits only dry water.
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5.Buchholz relay:
Buchholz relay is used for protection of oil filled transformer from
incipient fault (minor fault) below oil level. This relay is installed
between the transformer tank and conservator. The incipient faults in
transformer tank below an alarm. The arc due to fault causes
decomposition of transformer oil. The product of decomposition
contains more than 70% hydrogen gas which being light rises upward
and tries to go into the conservator, Buchholz relay is fitted in the pipe
leading to the conservator. The gas gets collected in the upper portion
of the Buchholz relay drops down. The fact floating in the oil level in
the Buchholz relay tilts down with lowering oil level while doing so the
mercury switch closes the alarm circuit. Thereby the operator knows
that there is some incipient fault in the transformer can be
disconnected before the incipient fault grows into a serious one.

6.Differential protection: -

The Differential protection responds to the vector difference between

two similar quantities. In protection of transformer CTs are connected
at each end of transformer. The CT secondary are connected in star or
delta and pilot wires are connected in between the CT of each end. The
CT connections and CT T ratios are such that current fed into the pilot
wires from both the ends are equal during normal condition and for
through fault. During the internal fault such as phase to phase or phase
to ground the balance is disturbed.
The out of balance current flows through the relay operating coils. To
avoid unwanted operation on through faults restraining bias coils or
restraining coil is proportion to (11+12)/2 As a result the restraining
torque increases with through current and relay does not operate due
to the difference in CT ratios for high values of short circuit current.
High speed relay element is provided in the differential system.
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7. Oil temperature thermometer:

The thermocouple is placed in pocket
provided with the tank neat hot oil
Thermocouple leads are connected to oil
temperature indicator placed in control
cabinet.

8.Winding temperature indicator:

Winding temperature indicator installed in marshalling kiosk get input
for measurement from

1. Thermocouple placed in the tank near hot oil.

2. CT secondary which measure the current in the winding.
3. The indicator is provided with an alarm and tripping contact .
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5. Important Part Of Transmission Line

5.1 Earthing

In power system, earthing means connecting frame electrical equipment some

electrical part system soil. This connection earth may through conductor
someother circuit depending upon situation. Regardless method connection earth,
grounding earthing offers two principal advantages.
First it provides protection to the power system for example, neutral point star
connected system grounded through circuit breaker and phase to earth fault
occurs on any one-line, large fault current will flow through circuit breaker. The
circuit breaker will open to isolate the faulty line. This protects the power system
from the harmful effects of the fault. Secondly, earthing of electrical equipments
ensures safety of the persons handling the equipment ensure example, if
insulation fails, there will direct contact of the live conductor with the metallic part
of the equipment Any persons contact with the metallic part this equipment will
be a subjected dangerous electrical shock which can be fatal

The process connecting metallic frame electrical equipment some electrical part of
the system to earth (i.e. soil) is earthing or grounding.
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Grounding or earthing may classify

1. Equipment grounding ORJA

2. System grounding

1. Equipment grounding
Equipment grounding deals with earthing the non-current carrying metal parts
of the electrical equipment. On the other hand, system grounding means
earthing some part of the electrical system i.e., earthing of neutral point of
star-connected system in generating stations and substation.

2.System grounding:
The process connecting some electrical part of the power system to earth
called system grounding. The system grounding has assumed considerable
importance in the fast expanding power system. By adopting proper schemes
of system grounding, we can achieve many advantages including production,
reliability and safety to the power system network.

3.Neutral grounding:
The process connecting neutral point of w3-phase system to the earth either
directly through some circuit element called neutral grounding. Neutral
grounding provides protection to personal and equipment. It because during
earth fault, the current path completed through the earthed neutral and the
protective devices operate isolate the faulty conductor from the rest the
system.
ADVANTAGES OF NEUTRAL GROUNDING
The following are the advantages of neutral grounding are:
i) Voltages of the healthy phases not exceed line ground voltages i.e. they
remain nearly constant.

ii) The high voltages due arcing grounds are eliminated.

iii) The protective relays can used provide protection against earth faults.
In case, earth fault occurs on any line, the protective relay will operate
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isolate to the faulty line. iv) Over voltage due to lightning are discharged
to earth.

5.2 TRANSMISSION TOWERS

A transmission tower is a tall structure and it is made up of steel

which is used to support an overhead power line. In electrical grid
transmission tower carries4 high voltage line from generating station
to power station.
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Tower Types

There are several types of transmission tower and many variations,

but they can be roughly grouped as:

 Suspension Towers – conductors are suspended between two

towers using suspension insulators.

 Terminal Towers – conductors from a transmission line are

connected to a substation or underground cable via a
tower’s strain insulators.

 Tension Towers – the tower can cater for the weight of the
cables and axial loading (strain in a horizontal direction).

 Transposition Towers – the tower changes the position of the

conductors on a transmission line relative to each other e.g. in
position x, out position y.

There are too many tower variations to be discussed here, but some
of the most common will now be discussed further.
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SELF SUPPORTING TOWER FOR SINGLE CIRCUIT OR

DOUBLE CIRCUIT

Self supporting tower (also called rigid tower) stands on its own
foundation rigidly and vertically.

TANGENT TOWER SELF SUPPORTING SINGLE CIFCUIT OR

DOUBLE CIRCUIT

These are used for normal spin and straight line. About 75% of
tower in transmission line are of this type. These towers support the
conductors and are not designed for loads caused by a longitudinal
pull of conductor. Under normal condition the tangent support take
up the downward transverse load caused by mass of conductor,
insulator, hardware and wind pressure exerted on the conductor
and supports.
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5.3 CONTROL & RELAY ROOM

The control room has various control panels which shows the
information like incoming power outgoing power, frequency, time
common to all sub stations, status of various lines (healthy, faulted,
under outage or maintenance), status of various protective
instruments like isolators, circuit breaker, temperature instruments,
of various working tap of transformer etc.
The DAS( Data Acquisition System) is used to accumulate the data
received from various sources The relay rooms separate from the
control room All relay used here are numerical and Simens or ABB
are either from
The protection system is so fast that it can detect a fault within 30 ms
and hence the circuit breaker can he operated within as less as 80
ms. For 400KV side C.B., one time auto reclosure is allowed in order
to clear the faults automatically.
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5.4 BATTERY ROOM

i) The control panels and relays of the substation required DC supply

of 110 V.

ii) The DC supply is made with the help of battery bank reserve
normally kept in a separate room called battery room.
iii) The batteries used in this sub-station are Nickel Cadmium (Ni-Cd)
batteries. These batteries re used due to their advantages like low
maintenance, longer life (15-20 years) etc.

iii) Each cell is of 2 V and 300 Ah Capacity.

Use of battery in sub-station:

Storage battery system is used in emergency situation for the
working of electrical equipment:

• To open and close the switch gear

• For indication and control Emergency lighting 
Relay and interlocking equipment  For
working of alarm circuit.
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5.4 Protective Relaying:

Protective relays are used to detect defective lines or apparatus and

to initiate the operation of circuit interrupting devices to isolate the
defective equipment Relays are also used to detect abnormal or
undesirable operating conditions other than those caused by
defective equipment and either operate an alarm or initiate
operation of circuit Interrupting devices. Protective relays protect the
electrical system by causing the defective apparatus or lines to be
disconnected to minimize damage and maintain service continuity to
the rest of the system There are different types of relays:

1. Over current relay

2. Distance relay
3. Differential relay
4. Directional Over current relay Ltd.

1) Over Current Relay:

The over current relay responds to a magnitude of current above a specified
value. There are four basic types of construction: They are plunger, rotating
disc static, and microprocessor type. In the plunger type, a plunger is moved by
magnetic attraction when the current exceeds a specified value. In the rotating
induction-disc type, which is a motor, the disc rotates by electromagnet
induction when the current exceeds a specified value.
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Static types convert the current to a proportional D.C milli volt signal and apply
it to a level detector with voltage or contact output. Such relays can be
designed to have various current-1 type of rotating induction-disc relay, called
the voltage restrained over Current relay. The magnitude of voltage restrains
the operation of the disc until the magnitude of the voltage drops below a
threshold value. Static over current relays are equipped with multiple curve
characteristics and can duplicate almost any shape of electromechanical relay
curve Microprocessor relays convert the current to a digital signal. The digital
signal can then be compared to the setting values input into the relay. With the
microprocessor relay, various curves or multiple time-delay settings can be
input to set the relay operation. Some relays allow the user to define the curve
with points or calculations to determine the output characteristics.

ii) Distance Relay:

Has the overall effect of measuring impedance. The relay operates

Instantaneously (within a few cycles) on a 60-cycle basis for values of
impedance below the set value: When time delay is required, the relay
energizes a separate time-delay relay or function with the contacts or
output of this time-delay relay or function performing the desired output
functions. The relay operates on the magnitude of Impedance measured
by the combination of restraint voltage and the operating current passing
through it according to the settings applied to the relay. When the
impedance is such that the impedance point is within the impedance
characteristic circle, the relay will trip. The relay is inherently directional.
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The line impedance typically corresponds to the diameter of the circle

with the reach of the relay being the diameter of the circle.
iii) Differential Relay:

The differential relay is a current-operated relay that responds to the

difference between two or more device currents above a set value.
The relay works on the basis of the differential principle that what
goes into the device has to come out. If the current does not add to
zero, the error current flows to cause the relay to operate and trip
the circuit.

The differential relay is used to provide internal fault protection to

equipment such as transformers, generators, and buses. Relays are
designed to permit differences in the input currents as a result of
current transformer
mismatch and applications where the input currents come from
different system voltages, such as transformers A current differential
relay provides restraint coils on the incoming current circuits. The
restraint coils in combination with the operating coil provide an
operation curve, above which the relay will operate. Differential
relays are often used with a lockout relay to trip all power sources to
the device and prevent the device from being automatically or
remotely reenergized. These relays are very sensitive. The operation
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of the device usually means, major problems with the protected

equipment and the likely failure in re-energizing the equipment.

iv ) Directional Over current Relay:

Directional over current relay operates only for excessive current

flow in a given direction Directional over current relays are available
in electromechanical A, static, and microprocessor constructions. An
electromechanical overcorrect relay is made directional by adding a
directional unit that prevents the over current relay from operating
until the directional unit has operated, the directional unit responds
to the product of the magnitude of current, voltage, and the phase
angle between them or to the product of two currents and the phase
angle between them. The value of this product necessary to provide
operation of the
directional Unit is small, so that it will not limit the sensitivity of the
relay (such as an over current relay that it controls). In most cases,
the directional element is no united inside the same case as the relay
it controls. For example, an over current relay and a directional
element are mounted in the same case, and the combination is called
a directional over current relay. Microprocessor relays often provide
a choice as to the polarizing method that can be used in providing
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the direction of fault, such as applying residual current or voltage or

negative sequence current or voltage polarizing functions to the
relay.

CONCLUSION

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.

The major stations include a control room from which

operations are coordinated. Smaller distribution substations
follow the same principle of receiving power at higher
voltage on one side and sending out a number of distribution
feeders at lower voltage on the other, but they serve a more
limited local area and are generally unstaffed. The central
component of the substation is the transformer, as it provides
the effective in enface between the high and low voltage
parts of the system. Other crucial components are circuit
breakers and switches. Breakers serve as protective devices
that open automatically in the event of a fault, that is, when a
protective relay indicates excessive current due to some
abnormal condition. Switches are control devices that can be
opened or closed deliberately to establish or break a
connection. An important difference between circuit breakers
and switches is that breakers are designed to interrupt
abnormally high currents (as they occur only in those very
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situations for which circuit protection is needed), whereas

regular switches are designed to be operable under normal
currents. Finally, substations may also include capacitor banks
to provide voltage support.

In context to the visit according to our JUT syllabus

During my summer internship at a power grid substation, I
gained valuable insights into the fundamental aspects of grid
operations. This included learning about substation
infrastructure like transformers and switchgear, as well as
monitoring systems such as SCADA. I also became familiar
with crucial safety protocols around high-voltage equipment
and participated in maintenance activities to ensure grid
reliability. Understanding grid stability measures and
environmental considerations further broadened my
understanding of the industry's operational challenges.
Collaborating with engineers and technicians provided first
hand experience in managing and optimizing substation
performance, highlighting the teamwork essential for
maintaining a reliable electricity supply. And these are the
part of our syllabus, so this internship helped us to
understand the topics of our syllabus in easily way.
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REFERENCES

 https://electrical-engineering-portal.com/download-
center/books-and-guides/power-substations/electrical-
design-of-132-33kv-substation

 https://en.wikipedia.org
 https://www.geeksforgeeks.org/transformer/
 https://www.electronics-tutorials.ws/
transformer/transformer-basics.html
 https://www.brainkart.com/article/Insulator---
Introduction_12377/
 https://www.toppr.com/guides/physics/current-
electricity/electrical-insulators/
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