MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION

GOVERNMENT POLYTECHNIC NANDED

INDUSTRIAL TRAINING 2022-2023

Preparing a Detailed Report on Maharshtra State Eelecticity

Transmission Co.LTD Company which is 132kv substation Gangakhed by
Highlighting SomePoints i.e. service requirement.

Program: Electrical Engineering Progam Code:EE5I Course:

Industrial Training Course Code:22057

Mentor: Mr.Y.S.Katke Sir

 MAHARSHTRA STATE BOARD OF TECHNICAL EDUCATION

CERTIFICATE

This is to certify that Mr. Chandrashekhar Laxman Latpate (872) is student

of Engineering Diploma in Electrical Engineering of Institute, Government
Polytechnic Nanded .Before 5th Semester she has completed her Industrial
Training (22057) satisfactorily by Preparing a Detailed Report on India’s Largest
Integrated Power Company which is MSETCL 132kv Substation Gangakhed
by Highlighting Some Points i.e.Manufacturing Edges & Services for Academic
Year 2022-2023 as prescribed in curriculum….

Place: Nanded
Date:

Mentor Principal
Prof. Mr.Y.S.Katke Sir Dr.G.V.Garje
 Acknowledgment

This internship report serves the purpose to record the details of my

industrial. This report will cover the details of my internship in the MSETCL
132kv Substation Gangakhed for a duration of 6 week months which began
from 4rd Jule , 2021 till 14thAugest ,2021 among week 1in this report at 132kv
Substation Gangakhed through offline mode.
This is to ensure that the students will be getting the exposure to involve
in accounting related works instead of other non-accounting related works.
The objectives of having this industrial training are to give exposure to the
students to the real working life, enable the students to develop a deeper
understanding on the course which they are undertaking and to provide the
appropriate work-related trainings to them in the field of accounting
profession.
 Abstract
Industrial training course is introduced to us with an objective to develop the
traits of industry culture among us before we enter into world of industry. By
exposing and interacting with the real life industrial setting, we will appreciate
and understand the actual working of an industry, best practices adopted in
industry. The industrial skills like, soft skills, life skills and hands-on will be
instrumental in orienting us in transforming them into industry ready output
after completion of diploma programme.
This report is a summary of study that carried out on the “MSETCL 132kv
Substation Gangakhed” profile including Vision, Mission, Quality
Assurance and many more things of that company.
 INTRODUCTION

Mahapareshan or Mahatransco (Maharashtra State

Electricity Transmission Company Limited - MSETCL) is a
wholly owned by government of Maharashtra and the major
electricity transmission company in the state of Maharashtra,
India.after 2003 it is converted to state-owned Electricity
Companies.
Maharashtra State Electricity Transmission Company limited, a
wholly owned corporate entity under the Maharashtra
Government, was incorporated under the Companies Act, in June,
2005 after restructuring the erstwhile Maharashtra State
Electricity Board to transmit electricity from its point of
Generation to its point of Distribution.
It owns and operates most of Maharashtra’s Electric Power
Transmission System. MSETCL operates a transmission
network of 39871 Circuit KM of transmission lines and 559 EHV
Substations with 89178 MVA transformation capacity. This
infrastructure constitutes most of the inter regional as well as intra
regional electric power transmission system in the State.
The company also has the distinction of being the only power
utility in the state sector to own HVDC lines. The Company
operates a 752 km long, 1500 MW, 500 KV bi-polar HVDC line
from Chandrapur to Padghe. This has been marked as a major
success as electric power is generated in east Maharashtra, due to
easy availability of coal, whereas the bulk use of power is in the
western part of Maharashtra in and around cities such as Mumbai,
Pune and Nashik. The power losses are very low in the HVDC
line. As a result, the power received at Padghe is practically the
same as what is injected at Chandrapur.
 ABOUT OF SUBSTATION

The substation in Gangakhed is one of the important power

grids in the state of Maharashtra Cause it supplies the Gangakhed
& locality. Themost important of any substation is the grounding
(Earthing System) of theinstruments, transformers etc. used in the
substation for the safety of theoperation personnel as well as for
proper system operation and performance ofthe protective
devices. An earthen system comprising of an earthing mat
buriedat a suitable depth below ground and supplemented with
ground rods at suitable points is provided in the substations. These
ground the extra high voltage to theground. As it is dangerous to
us to go near the instrument without properearth. If the
instruments are not ground properly, they may give a huge shock
toanyone who would stay near it and also it is dangerous for the
costly Instrumentas they may be damaged by this high voltage
Single line diagram of 132kv/33kv substation gangakhed
:-

Index of single line digram :-

Explation of Single line digram :-

A Single Line Diagram (SLD) of an Electrical System is the Line

Diagram of the concerned Electrical System which includes all
the required electrical equipment connection sequence wise from
the point of entrance of Power up to the end of the scope of the
mentioned Work. As in the case of 132KV Substation. the SLD
shall show Lightening Arrestor. CT/PT Unit. Isolators, Protection
and Metering P.T & C.T. Circuit Breakers, again Isolators and
circuit Breakers, Main Power Transformer, all protective
devices/relays and other special equipment like CVT. GUARD
RINGS, etc as per design criteria. And the symbols are shown
below. There are several feeders enter into the substation and
carrying out the power. As these feeders enter the station they are
to pass through various instruments.
Starting from the generating stations to the end users, voltage is
needed to be stepped up and down several times in various
substations. This ensures efficient transmission of power ,
minimizing the power losses. Our project is to design a
132KV/33KV EHV substation where the income power recived at
132 kv form a generating station.
The power factor is corrected here and the voltage is step down to
33kv and power is then transferred to distribution system of the
grid to meet the requirements of the end consumers at their
suitable voltage.
The power from main bus was fed into a20mva transformer
which stepped the voltage down to 33kv .
The power is then fed into a 33kv bus from which different loads
were tapped. In the process, the surge impedance loading of 132
KV and 33 KV lines were calculated and they were used to
estimate the maximum power that can be transferred by one
transmission line.
 Equipments in a 132KV Sub-Station:-
The equipment required for a transformer Sub-Station depends
upon the type of Sub-Station, Service requirement and the degree
of protection desired. 132KV EHV Sub-Station has the following
major equipments

1) Bus bar :-

When a no. of lines operating at the same voltage have to be

directly connected electrically, bus-bar are used, it is made up of
copper or aluminium bars (generally of rectangular X-Section)
and operate at constant voltage. The bus isa line in which the
incoming feeders come into and get into the instruments for
further step up or step down. The first bus is used for putting the
incoming feeders in LA single line. There may be double line in
the bus sothat if any fault occurs in the one, the other can still
have the current and the supply will not stop.
2) Insulators :-
The insulator serves two purpose. They support the conductor
(or bus bar) and confine the current to the conductor. The most
commonly used material for the manufactures of insulators is
porcelain. There are several type of insulator (i.e. pine type,
suspension type etc.) and their use in Sub-Station will depend
upon the service requirement. Post insulators are used for the
bus bars. A post insulator consists of a porcelain body, cast iron
cap,
&flanged cast iron base. The whole cap is threaded so that bus
bars can be directly bolted to the cap. When the line is subjected
to a greater tension, strain insulators are used. When tension in
line is exceedingly high, two or more strings are used in parallel.

3) Isolating Switches:-
In Sub-Station, it is often desired to disconnect a part of the
system for general maintenance and repairs. This is accomplished
by an isolating switch or isolator. An isolator is essentially a knife
Switch and is design to often open a circuit under no load, in other
words, isolator Switches are operate only when the line is which
they are connected carry no load. For example, consider that the
isolator are connected on both side of a cut breaker, if the isolators
are to be opened, the C.B. must be opened first. If an isolator is
opened carelessly, when carrying high current the resulting arc
easily causes flashover to earth.
4) Circuit breaker :-
A circuit breaker is a 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. A circuit breaker consists of fixed &
moving contacts, which are touching each other under normal
condition i.e. when breaker is closed. Whenever a fault occurs trip
coil gets energized, the moving contacts are pulled by some
mechanism & therefore the circuit is opened or circuit breaks.
When circuit breaks an arc is stack between contacts, the
production of arc not only interrupts the current but generates
enormous amount of heat which may cause damage to the system
or the breaker itself. Therefore the main problem in a circuit
breaker is to extinguish the arc within the shortest possible time so
that the heat generated by it may not reach a dangerous value. The
medium used for arc extinction is usually
Oil, Air, Sulfur Hexafluoride (SF6) or vacuum.
Circuit breakers can be classified on the basis of medium used
for arc extinction:

a. Oil Circuit Breakers:-

These are the oldest type of circuit breakers & have the virtues
of reliability, simplicity of construction & relative cheapness.
These are mainly of two types:

b. Bulk Oil Circuit Breakers:-

using large quantity of oil are also called the dead tank type
because the tank is held at earth potential. Such circuit breakers
may further be classified as:-
c. Plain Break Oil Circuit Breakers:-
are very simple in construction & widely used in low voltage
dc & ac circuits. For use on higher voltages, they become unduly
large in size & need huge of transformer oil. In addition, such
breakers are not suitable for high- speed interruption; therefore,
these cannot be used in auto-closing.
d. Self Generated Pressure Oil Circuit Breakers:-

These are of three types viz. Plain explosion pot having

limited breaking capacity, cross jet explosion pot suitable for
interrupting heavy current high voltage (66kV) & self
compensated explosion pot suitable for operation both at heavy
currents as well as low currents. Plain explosion pot cannot be
used either for very low currents because of increased arcing time
or for very heavy currents because of risk of bursting of pot due to
high pressure.

e. Air Blast Circuit Breakers:

The air blast circuit breakers employs compressed air (at a

pressure of 20 kg/cm) for arc extinction & are finding their best
application in systems operating 132 kV & above (upto 400kV)
with breaking capacity up to 7,500 MVA (during short circuit
fault) & above although such breakers have also been designed to
cover the voltage range of 6,600 Volts to 132,000 Volts. These
breakers have the advantages of less burning of contacts because
of less arc energy, little maintenance , facility of high speed
reclosure no risk of explosion & fire hazard & suitability for
duties requiring frequent operations. The drawbacks of such
breakers are additional need of compressor plant for supplying
compressed air, current chopping, sensitivity restriking voltage &
air leakage at the pipe line fittings.

f. Vacuum Circuit Breakers:

The idea behind the vacuum circuit breakers is to eliminate the
medium between the contacts-vacuum. The dielectric strength of
vacuum is 1000 times more than that of any medium. In
construction it is very simple circuit breaker in comparison to an
air,
or oilcircuit breakers. These breakers are used for reactor
switching transformer switching, capacitor bank switching where
the voltages are high & the current to be interrupted is low.
Specification of 132 kV Vacuum Circuit Breaker:

Type=ELFSF2-1 (r)
Rated Voltage=145 kV Rated Frequency=50 Hz
Rated Normal current=3150 Amps at 40oc
Rated Lightning Impulse Withstand Voltage=650 KV p Rated
Short Circuit Breaking Current=31.5 k Amps
Rated Short Time Withstand Current & Duration=31.3 k
Amps for 3 sec Line Charging Breaking Current=50 k Amps
First Pole To Clear Factor=1.5Rated Gas Pressure SF6/20oc
(abs) =7.0 bar
Closing & Opening Devices Supply Voltage=220 v (d.c)

Auxiliary Supply Voltage=One Phase, 240v ac &Three Phase,

415v ac Air Pressure=22 bar
Total Mass=1750 kg (approx)
Closing Time ≤ 130 m sec Maker= M/S ABB It is used for
transformer-1

Sulphur Hex-fluoride Circuit Breakers:

SF6 gas has unique properties such as very high dielectric

strength, non-reactive to the other components of circuit breakers,
high time constant & fast recombination property after removal of
the source energizing the spark, which proves it superior to the
other mediums (such as oil or air) for use in circuit breakers.SF6
circuit breakers have the advantages of very much reduced
electrical clearances, performance independent of ambient
conditions, noise less operation, reduce moisture problem,
minimum current chopping, small arcing time, no reduction in
dielectric strength of SF6 , low maintenance, reduced installation
time & increased safety.
 Such as circuit breakers are used for rated voltages in the
ranges of 3.6 to 760 kV .For the later operation a relay wt. is used
with a C.B. generally bulk oil C.B. are used for voltage up to 66
KV while for high voltage low oil & SF6 C.B. are used. For still
higher voltage, air blast vacuum or SF6 cut breaker are used. The
use of SF6 circuit breaker is mainly in the substations which are
having high input kv input, say above 132kv And more. The gas
is put inside the circuit breaker by force ie under high pressure.
When if the gas gets decreases there is a motor connected to
the circuit breaker. The motor starts operating if 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 theSF6 gas to reduce the torque produce in it due to
any fault in the line. The circuit breaker has a direct link with the
instruments in the station, when any fault occur alarm bell rings.

Specification of 132kV SF6 Circuit Breaker:

Type=120-SFM-32B (3 Pole) STD.

Rated Voltage=145 kV Rated Frequency=50 Hz
Rated Normal Current=1600 Amps Rated Making Current=80
k Amps
Rated Short Circuit Breaking Current=31.5 k Amps Rated
Short Time Current=31.5 k Amps for 3 Sec Rated Lightning
Impulse Withstand Voltage=650 kv p First Pole To Clear
Factor=1.5
Rated Gas Pressure=6 kg/cm2-gm at 20oc tem Gas Weight=7.5
kg
Total Weight=1450 kg
Rated Coil Voltage Closing=220 v (d.c) Tripping=230 v (d.c)
Motor Voltage=230 v (a.c)
Auxiliary Voltage=1 phase 230 v (a.c) Rated Closing
Time<130 m Sec Rated Operating Time<130 m Sec Maker=M/S
CG l

This breaker is used in 132 kV, Mohaddipur Sub-Station 132

kV Transformer- II protection
5) Protective relay :-
A protective relay is a device that detects the fault and initiates
the operation of the C.B. is to isolate the defective element from
the rest of the system”. The relay detects the abnormal condition
in the electrical circuit by constantly.
easuring the electrical quantities, which are different under
normal and fault condition. The electrical quantities which may
change under fault condition are voltage, current, frequency and
phase angle. Having detect the fault, the relay operate to close the
trip circuit of C.B. There are two principle reason for this; Firstly
if the fault is not cleared quickly, it may cause unnecessary
interruption of service to the customer. Secondly, rapid
disconnection of faulty apparatus limits the amount of damage to
it & aprevents the effects from speeding into the system. A
protective relay is a device that detects the fault & initiates the
operation of circuit breaker to isolate the defective element from
the rest of the system. Most of the relays operate on the principle
of electromagnetic attraction or electromagnetic induction. The
following important types of relays are generally used in electrical
distribution & transmission line:

1. Induction Type Over Current Relay

2. Induction Type Over Voltage Relay
3. Distance Relay
4. Differential Relay
5. Earth Fault Relay

6. Induction Type Over Current Relay:

This type of relay operates on the principle of electromagnetic
induction initiates corrective measures when current in the circuit
exceeds a predetermined value .
The actuating source is a current in the circuit supplied to the
relay by a current transformer .These relays are used on ac circuits
only and can operate for fault flow in either direction. Under
normal condition the resulting torque is greater than the driving
torque produced by the relay coil current.
 Hence the Aluminium disc remains stationary, by during
fault current in the protective circuit exceeds the preset value. The
driving torque becomes greater than the starting torque & the disc
starts to rotate, hence moving contact bridges are fixed contact
when the disc rotates to a preset value. Trip circuit operates the
circuit breaker, which isolates the faulty section.
a. Induction Type Over Voltage Relay:

This type of relay operates on the principle of electromagnetic

induction & initiates corrective measures when current in the
circuit exceeds a predetermined value. Under normal condition
the aluminium disc remains stationary. However if the voltage
increases at any cost the disc starts to rotate,
hence moving contact bridges to the fixed contact when the
disc rotates through a preset angle. Trip circuit operates the circuit
breaker, which isolates the faulty section.

b. Distance Relay:

Under normal operating condition, the pull is due to the

voltage element. Therefore the relay contacts remains open.
However when a fault occurs in the protected zone the applied
voltage to the relay decreases where the current increases. The
ratio of voltage to current faults is below the predetermined value.
Therefore, the pull of the current element will exceed that due to
voltage element & this causes the beam to tilt in direction to close
the trip circuit.
c. Differential Relay:

It compensates the phase difference between the power

transformers primary & secondary. The C.T.s on the two sides are
connected by pilot wires at both ends are same & no current flows
through the relays. If a ground or phase-to-phase fault occurs, the
currents in the C.T.s no longer will be the same & the differential
current flowing through the relay circuit will clear the breaker on
both sides of transformers. The protected zone is limited to the
C.T.s on the low voltage side & C.T.s on the high voltage side of
the transformer.

This scheme also provides protection for short circuits

between turns of the same phase winding. During a short circuit,
the turn ratio of power transformer is altered & cause unbalance in
the system which cause the relay
to operate. However, such sorts are better taken care by
Buchholz relay.

d. Earth Fault Relay:

This scheme provides no protection against phase to phase

faults unless & until they develop into earth faults. A relay is
connected across
transformer secondary. The protections against earth faults are
limited to the region between the neutral & line current
transformer. Under normal operating condition, no differential
current flows through the relay. When earth fault occurs in the
protected zone, the differential current flows through the
operating coil of the relay. The relay then closes its contacts to
disconnect the equipment from the system.
7) 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.

a. Current Transformer :-

A current transformer is essentially a step-down transformer.

It steps-down the current in a known ratio, the primary of this
transformer consist of one or more turn of thick wire connected in
series with the line. The secondary consist of thick wire connected
in series with line having large number of turn of fine wire and
provides for measuring instrument, and relay a current, which is a
constant faction of the current in the line.
 Current transformers are basically used to take the readings of
the currents entering the substation. This transformer steps down
the current from 800 ampsto1amp. 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 protectio

b) Voltage Transformer or Potential Transformer :-

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

voltage in known ratio. The primary of these transformer consist
of a large number of turn of fine wire connected across the line.
The secondary winding consist of a few turns, provides for
measuring instruments, and relay a voltage that is known fraction
of the line voltage. In Mohaddipur Substation.
Specification of 132 kV P.T.:

Line voltage=132 kV VA/Phase=750 Phase=1

Class=B Frequency=50 Hz*
Neutrally Earthed Voltage= Primary-73200V Secondary-
63.5V
8) Transformer :-

There are two transformers in the incoming feeders so that the

three lines are step down at the same time. In case of a 220KV or
more Auto transformers are used. While in case of lower KV line
such as less than 132KV line double winding transformers are
used of lower KV line such as less than 132KV line double
winding transformers are used Transformer is static equipment,
which converts electrical energy from one voltage to another. As
the system voltage goes up, the techniques to be used for the
Design, Construction, Installation, Operation and Maintenance
also become more and more critical. If proper care is exercised in
the installation, maintenance and condition monitoring of the
transformer, it can give the user trouble free service throughout
the expected life of equipment which of the order of 25-35 years.
Hence, it is very essential that the personnel associated with the
installation, operation or maintenance of the transformer is
through with the Instructions provided by the manufacture.

Basic Principle:

The transformer is based on two principles; firstly, that an

electric current can produce a magnetic field (electromagnetism)
and secondly that a changing magnetic field within a coil of wire
induces a voltage across the ends of the coil (electromagnetic
induction).Charging the current in the primary coil changes the
magnetic flux that is developed. The changing magnetic flux
induces a voltage in the secondary coil. The two circuits are
electrically isolated but magnetically linked through a low
reluctance path. If one coil is connected to a.c supply, an
a.c is setup in both of these circuits. This helps to transfer the
voltage from one side to another. We have observed five at KLSD
along with two station transformers. Out of these five, two are
132/33kV in y-d mode & others are 33/11 kV in d-Y mode.
 Accessories of transformers:

a. Core & Winding:

It may be of various shape i.e. core, shell. It is made of

cold-rolled-grain- oriented Silicon-steel of varnish insulation on
the lamination. Thecore is laminated to reduce the core loss. The
laminations are made in steps &try to give circular cross section.
Bolts 7 nuts secure the lamination. The coreis placed at the
bottom of the tank. The tanks are constructed from sheet steel.

Figure: 50 MVA Transformer:-

 For small tank & boiler sheet for large tank.. There are
thermometer pockets, radiator tubes for increasing cooling
surfaces. A 3-phase transformer has six separate windings, three
primary & three secondary wound iron cores. name led copper
with insulation is used for winding. Insulated papers are used
for interlayer insulation. Paper in the form of tape may be
utilized for tapping winding leads and other parts. Pressboards are
used for insulation between windings & core. Pressboards are also
used to separate HV windings from LV windings inputs nearer the
core.

b. Transformer Oil:

The tank is filled with transformer oil; & sealed. It is a mineral

oil obtained by refining crude petroleum. It serves the following
purposes:-

1. Provides additional insulation

2. Carries away the heat generated in the core & oils Good
transformer oil should have:-

High dielectric strength.

Low viscosity to provide good heat transformation. High
flash/fire point
Free from inorganic acid, alkali & corrosive Sulfur
Free from sludging under normal operating condition. It is
Important to check the oil in regular intervals.
c. Conservator:

It consists of an airtight metal drum fixed above the level of

the top of the tank & connected with the tank is completely filled
with oil. The conservator is partially is filled with oil. The
function of conservator is to take up construction & expansion of
oil without allowing it to come in contact without side
air. Transformer oil will expand due to the heat generated
because of losses.

d. Breather:

When the temperature changes, expansion of contacts & there

is a displacement of air . When the transformer cools the oil level
goes down 7 air is drawn in.
The oil should not be allowed to come in contact with the
atmospheric air as it may take moisture which may spoil its
insulating properties. Air may cause acidity or slugging of oil, so,
the air coming in is passed through an apparatus called breather
for extracting moisture. The breather consists of a small vessel,
which contains a drying agent like Silica gel crystal.

e. Diverter tank:
It is a drum like structure mounted on a transformer wall
&filled with transformer oil & connected to conservator. It
reduces arcing during tap changing operation.
f. Radiator:

It is of small thickness & large diameter plates & used for heat
dissipation during operation. Large diameter means large surface
area 7 better cooling.

g. Temperature Indicator:

There are two temperature indicators on the transformer tank

one for oil temperature measurement & another for core
temperature measurement. In 31.5 MVA Transformers when oil
temperature reaches 65o c cooling fans starts automatically but
when the oil temperature rises at 75oc or winding temperature
rises at 85oc the alarm circuit will be closed. Further increase in
oil or winding temp the circuit will trip automatically. Cooling
fans are placed beside the radiator tube, which are used for oil
cooling. Generally the cooling fans start automatically but when
needed it can be started manually.
h. Bushing:

it is fixed on the transformer tank and these connections is

made to the external circuits. Ordinary porcelain insulators can be
used as bushing upto voltage of 33 kV. Above 33 kv oil filled
type bushings are used. In filled bushings, the conductor is passed
through the hollow porcelain insulator which is filled with oil.

i. Buchholz relay:

It Is a gas actuated relay installed in oil immersed transformers

for protection against all kinds of faults. Any fault produces heat&
forces the evolution of gas. It mainly consists of two float
switches 7 placed in the connecting pipe between the main tank &
conservator. Under normal condition they main tank and Buchholz
relay is completely filled up with oil &the conservator tank is
about half full. When the fault occurs, produces gas &collect in
the container so the oil level gradually falls & closing the alarm
circuit. I f no attention is paid to it, the gas collection will be more
& closes another circuit which will cut out the transformer from
the line.

j. Explosion Vent/ Pressure Release Vent:

When the gas pressure on the container is heavy, explosion

vent is released. Alarm circuit & trip circuit will close by
Buchholz Relay, before opening the explosion vent it is used now
adays.

k. Tap Changing:
Mainly 132/33 kV transformer uses on-load tap changing
&33/11 kV transformer is used of load off-load tap changing. The
tap changer is generally done on H.V side because current flow is
less than lv side. Which reduces theflashing during the tap
changing. Here tap changed in 132/33 kV transformer
9) Specification of 132/33 kV Transformer:

In Mohaddipur substation two 132/33 kV power transformers

are used for 33 KV Supply.
MVA=31.5kV (no load) Frequency=50Hz Vector symbol=y-
D1
kV(no load) HV 132 kV, LV 33kV Amps HV 138 A , LV
552A Phase HV 3, LV 3 Mass of Oil=2360kg Total Mass=
12140kg
Volume of oil= 2650Liter
Core & Winding Weight= 5950kg Guaranteed Max. Temp.
Rise
in Oil=45oc, Winding=55oc

10) Protection Against Lightning:

Transients or Surges on the power system may originate from

switching or other causes, but the most important& dangerous
surges are those which caused by lightning. The lightning surges
may cause serious damage to the expensive equipments or strokes
on transmission lines that reach the equipments travelling as a
wave. Thus it is necessary to provide a protection against
lightning surges, They are:-

1. Earth Screen.
2. Overhead Ground Wire.
3. Lightning Arrestor.

1. Earth Screen:

The power stations & the substations are generally have much
expensive equipments. These stations can be protected from direct
lightning strikes by providing earthing screens. It consists of a
network of Copper conductors mounted all over the electrical
equipments in the substation or Power station.
 The screen is properly connected to earth on at least two
points through low impedance. On the occurrence of direct stroke
on the station the screen provides a low resistance path by which
lightning surges are connected to the ground. In this way station
equipments are protected against lightning.

2. Overhead Ground Wires:

The most effective method of providing protection against

direct lightning strokes is by the use of overhead ground wires.
The ground wires are placed over line conductors at such position
that practically all lightning strokes are intercepted by them. The
ground wire is ground at each tower or pole through as low
resistance as possible. when the direct lightning strokes occur on
the transmission line will be taken u by the ground wire. The
heavy current flows to the ground through the ground wire, so it
protects the line from harmful effects of lightning.

3. Lightening Arrestors:
 Firstly, we can see lightning arrestors. These lightning
arrestors can resist or ground the lightning, if falls on the
incoming feeders. The lightning 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
instruments in the substation are very high to protect them from
high voltage lightning these arrestors are used.
It is a device used in Electrical Power systems the insulation
o the system from the damaging effect of lightning. Metal Oxide
varistor (MOVs) have been used for power system protection the
mid 70s.
The typical lightning arrestor is also known surge arrestor has
a high voltage terminal and a ground terminal. When a lightning
surge or switching surge travels down the power system to the
arrestor, the current from the surge is diverted around the
protected insulation in most cases to earth. Lightning arrestors
with earth switch are used after the current transformers to protect
it from lightning i.e. from high voltage entering into it. This
lightning arrestor has an earth switch that can directly earth the
lightning. The arrestor works at 30o to 45o angle of the lightning
making a cone. The earth switch can be operated manually, by
pulling the switch towards the ground. This also helps in breaking
the line entering the station. By doing so maintenance repair of
any instrument could be performed.

11)Types of lightning arrestors:-

There are several types of lightning arrestors are in use, differs

only in their constructional detail but they are electrically identical
& operate on the same principle. They are-

a. Rod gap arrestor

b. Horn gap arrestor
c. Valve type arrestor
a. Rod type arrestor:

It consists of two rods which are bent in right angles with a

gap in between them. One rod is connected to the line circuit &
the other one is connected to the earth. They are usually connected
across the string of insulators & bushings of various transformers.
The rod gap should be set to breakdown at about 20% below the
impulse spark over voltage of insulation at the point where it is
installed. To protect the insulator it should be one 3 rd of the rod
gap. Under the normal condition the gap remains non conductive.
On the occurrence of high voltage surge on the line, the gap
sparks over & the surge current is connected to earth.

b. Horn gap arrestor:

It consists of two horn shaped metals rods separated by a small

air gap. The horns are so constructed that distance between them
gradually increase towards the top. The horns are mounted on the
porcelain insulators. On end of the horn is connected to the line &
other end is efficiently grounded. Under normal condition the gap
is non conductive. On the occurrence of high voltage, spark takes
place across the gap & the arc to travel up the gap. At some
position of arc, the distance may be for the voltage to maintain the
arc. Consequently, the arc is extinguished, & the excess charge on
the line is thus conducted to ground through arrestor.

c. Valve type arrestors:

It consists of a no. of flat disc of a porous material stacked one
above the other & separated by a thin mica rings. porous material
is made of specially prepared clay with a small add mixture of
powdered conducting substance. The discs are arranged in such a
way that the normal voltage may not cause the discharge to occur.
The mica rings provide insulations during normal operation. At
time of over voltage, the glow discharge occurs in the capillaries
of the material& the voltage drops to about 350 volts per unit.
 12) Specification of Lightning Arrestors In 132 kv System:

Style= SMX Type= ZOBIVER

Rated Voltage=102 k v (r.m.s)

Long duration Discharge=3 Frequency= 50Hz

Pressure Relief Current (r.m.s) = 40 KA Normal Discharge
Current= 10 KA

13) Storage Battery :-

A cell is a device in which a electrical difference of potential

is established between the two electrodes as a result of chemical
reaction between the electrode & electrolyte. There are two types
of cell:-
a. Primary cell
b. Secondary or storage cell Secondary cells are of two types:-
a. Lead Acid cell
b. Alkaline cell

Working Principle:

When the + ve plate of Lead per Oxide & - ve plates of

spongy lead are immersed in dilute H2SO4 & connected together
by means of external circuit, current flows round the circuit. The
cell works until the per Oxide is used up & under this condition
the cell is said to be discharging. The cell under fully discharged
condition: Positive Plate=PbO2
Negative plate=Pb
Electrolyte=dil. H2SO4 (sp. Gravity=1.25)
During discharge: The chemical action can be represented by
the following chemical equation. At + ve condition : -
PbO2+H2+H2SO4
=PbSO4+2H2O, At – ve condition:- Pb+SO4=PbSO4
 During Charging:- When a direct current from an external
source is passed through it from positive to negative, the
following, the following changes will occur:-
At +ve plate:- PbSO4+So2+2H2O = PbSO4+2H2O,At –ve
plate:- PbSO4+H2 = Pb+H2SO4
Color of the plate at the end of the charge becomes:-Positive
plate:-Dark Brown Negative plate:-Slate Gray The batteries are
connected to the circuit breaker for tripping the circuit breaker.
Here trip is used through type relays.

Specification of The Battery Charger:

Model=BC Rating=229 V, 24+24 AAC input=415 V±10%, 30

Amps, 50Hz, 3 Phase DC output=24.7 volt, 24 A

14) Capacitor bank attached to the bus:-

The capacitor banks are used across the bus so that the voltage
does not get down below the required voltage. When the inductive
property of the line increases then the voltage lags behind current
& causes loss of money, so to raise the voltage up &prevent loss
of money capacitor banks are used. It raises the voltage and raises
power factor.

15) Wave trap :-

 Wave trap is an instrument using for tripping of the
wave. The function of this trap is that it traps the unwanted waves.
Its function is
of trapping wave. Its shape is like a drum. It is connected to
the main incoming feeder so that it can trap the waves which may
be dangerous to the instruments here in the substation.
Low pass filter when power frequency currents are passed to
switch yard and high frequency signals are blocked. Line Isolator
with E.B. To isolate the line from Sub Station and earth, it under
shut down.

16) THE FIRE PROTECTION:-

The fire protection device should be kept in store yard for

safety of equipments during storage. It can be useful in the time of
danger. This includes fire extinguishers, constant supply of water
etc.

Storage of equipments for the sub station :

All the substation equipments/materials received on site

should be stored properly, either in the outdoor yard or in the
stores shade depending on the storage requirement of that
particular equipment. The material received should
be properly counted and checked for any damages/breakages
etc. The storage procedure for main equipment is as follows:

1. .EHV C.T.s and P.T.s Normally, 220KV are packed in iron

structures for extra supports with cross beams to avoid lateral
movement while those of 132KVC.Ts. and P.Ts are packed and
transported in wooden crates vertically 132 KVC.Ts. and P.Ts.
should be stored vertically and those of 220 KV and 400 KV
should be stored in horizontal position. C.Ts and P.Ts. packed in
wooden crates should not be stored for longer period as the
packing may deteriorate. The wooden packages should be stored
on a cement platform or on MS Channels
to avoid faster deterioration of the wooden crates. C.Ts and
 P.Ts packed in iron cases stored in horizontal position should be
placed on stable ground. No C.Ts and P.Ts. should be unpacked in
horizontal position.

2. L.A. are packed in sturdy wooden case as the porcelain portion is

very fragile. Care should be taken while unpacking, handling and
storage due to this reason.
3. Batteries, Acid, Battery charger C & R panel, A.C.D.B s copper
piping, clamp connectors, hardware etc. should be stored indoor

17) Circuit breakers:

The mechanism boxes of 33 KV – V.C.B s should be stored

on raised ground and properly covered with tarpaulins or should
be stored in door. The interrupter chambers should be stored on
raised ground to avoid rain water in storage area.

18)Extra High Voltage Circuit Breakers:

Now-a days SF6 circuit breaker are used at EHV voltages. The
control and operating cabinets are covered in polythene bags and
are packed in wooden and iron crates. These should be stored on
raised ground and should be covered with tarpaulins. The arcing
chambers and support insulators are packed in iron crates and
transported horizontally. The +ve pressure of SF6 gas is
maintained in these arcing chambers to avoid the ingress of
moisture. It should be ensured that this pressure is maintained
during the storage. Other accessories like pr.
Switches, density monitor, Air Piping, control cables, wiring
materials, SF6 gas pipes; SF6cylinder should be stored in store
shed.
19)Power transformers:

The main Tank -The transformer is transported on trailer to

substation site and as far as possible directly unloaded on the
plinth. Transformer tanks up to 25 MVA capacity are generally oil
filled, and those of higher capacity are transported with N2 gas
filled in them +ve pressure of N2 is maintained in transformer
tank to avoid the ingress of moisture. This pressure should be
maintained during storage; if necessary by filling N2 Bushings -
generally transported in wooden cases in horizontal position and
should be stored in that position. There being more of Fragile
material, care should be taken while handling them.

These should be stored with ends duly blanked with gaskets

and end plates to avoid in gross of moisture, dust, and any foreign
materials inside. The care should be taken to protect the fins of
radiators while unloading and storage to avoid further oil
leakages. The radiators should be stored on raised ground keeping
the fins intact. Oil Piping. The Oil piping should also be blanked
at the ends with gasket and blanking plates to avoid in gross of
moisture, dust, and foreign All other accessories like temperature
meters, oil flow indicators, PRVs, Buchholz relay; oil surge
relays;
Gas kit O ‘ rings etc. should be properly packed and stored
indoor in stores hed. Oil is received in sealed oil barrels . The oil
barrels should be stored in horizontal position with the lids on
either side in horizontal position to maintain oil pressure on them
from inside and subsequently avoiding moisture and water ingress
into oil. The transformers are received on site with loose
accessories hence the materials should be checked as per bills of
materials.

20) CONTROL AND RELAY PARTS:

These are used to control the operations of breakers, isolates,
through protective relays installed on these panels various
protection schemes for transformers, lines etc, are provided on
these panels.
 21) AC & DC DB’S –

These are used for extending A.C. & D.C. supplies whenever required
through various circuits. There are two main Buses in this arrangement
connected by each diameter.
i) Through either of line breakers the line side Main Bus can be charged
normally (Bus-I).
ii) The line breaker, tie breaker and 2nd Bus breaker/Transfer Bus if closed
in series will charge the 2nd Main Bus/Transfer bus.
iii) Outage on anyone Bus can be availed without interruption on any Bus.
The second Bus can feed all the loads.
iv) Breaker from any bay can be taken out for maintenance without
interrupting the supply.
v) For efficient working two diameters are required having source in each
diameter preferably connected diagonally opposite to two different buses.
vi) ) If both the sources are connected to same Bus (i.e. from one side only
one tie breaker can be attended at a time).
vii) If all the four breakers connected to Bus are out the transformer can be
charged through the breaker from remote substation source.
viii) Changing over as in case of 2 Bus or 3 Bus systems is not necessary as
supply is not interrupted, in any case as said above.
ix) All the breakers in the diameters are in energized position including
tiebreakers to keep the system in tact in case of any fault.
x) On line or transformer fault the tie breaker with respective line or
transformer breaker will trip.

xi) On Bus fault on any Bus only the two breakers (of two diameters)
connected Bus will Trip.

xii) The Teed-point remains unprotected in any of line or transformer or bus

faults hence the Teed point protection is given by differential relay. In case
of this protection the breakers (2 Nos.) connected to Teed point (tie breaker
+ Bus breaker) will Trip.
 Contoral room :-

Bus volatages and frequencies , line loadinng ,transformer loading,

power
Factor , real and power flow , temperature, etc, are the basic variable
related
of substation controal and instrumation the various supervision, control and
protection functions are performed in the substation control room.
The relays, protection and control panels are installed in the controlled
room. These panels along with PC aids in automatic operation of various
circuit breakers, tap changers, autoreclosers, sectionalizing switches and
other devices during faults and abnormal conditions
132 KV GANGAKHED SUB-STATION :-

TYPE : Outdoor grid substation.

Incoming Line Voltage: 132 kV
Outgoing feeder Voltage: 33 kV
Gangakhed substation receives power from Kandhar sub-station ,
Parli sub-station , Parbhani sub-station (MSETCL)

Gangakhed Substation has Seven 33 kV Outgoing feeders:-

1. Gangakhed
2. Khadka
3. Kodri
4. Ghodawat
5. Palam
6. Pinmpaldari
7. Midc

There are TwoTransformers in the substation:-

I. 132/33 k.v ,50 MVA = 2 nos.

 Meter and indicating instrument :-

There are several meter and indicating instruments eg.( Ammeter

, volatmeter, energy meter etc. ) installled in a sub-station to maintan which
over the circuit quantities. The instrument transformer are invariably used
with them for satisfactory opration.