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Mr.S R Tiwari
Mr.Sujeet Kr. Singh
Summer Training report,132 KV
Uttar PradeshPower CorporationLtd
Shashikant Bharti ,3rd
BBS college of engineering and
Technology, Allahabad , UPTU
“There are people, who, simply by being what they are, influence, encourage &
inspire you to do things you never thought yourself capable of doing….”
APPRENTICESHIP TRAINING PLACE A IMPORTANT ROLE IN EXPOSING THE
STUDENT IN REAL LIFE SITUATION IN A INDUSTRY . IT WAS A GREAT
EXPERIENCE FOR ME TO WORK AS A TRAINER AT UPPCL . TROUGH WHICH I
COULD LEARN HOW TO WORK IN A PROFESSIONAL ENVIRONMENT .
NOW I WOULD LIKE TO THINK THE PEOPLE WHO GUIDED ME AND
HAVE BEEN A CONSTANT SOURCE OF INSPIRATION THROUGH THE TRAINER
OF MY TRAINING .
I AM SINCERELY GRATEFUL TO Mr.S.R.TIWARI S.D.O. AT 132 KV
SUB-STATION MINTO PARK ALLAHABAD. WHO RENDERED HIS VALUABLE
ASSISTANCE , CONSTANT ENCOURAGEMENT AND ABLE GUIDANCE , WHICH
MADE THIS TRAINING A POSSIBILITY.
I WISH MY DEEP SENSE OF GRATITUDE TO Mr.SUJEET KUMAR
SINGH J.E UPPCL WHOS AFFECTIONATE HAS ENABLE US TO COMPLETE
THIS TRAINING SUCCESFULLY.
Uttar Pradesh Power Corporation Limited or in short UPPCL was recognised on
January 14, 2000. UPPCL was formed because of the need of reforms in power and energy
sector in Uttar Pradesh. These modifications were necessarily responsible for the
management and planning of electrical power industry while considering electricity
(power) generation, transmission, distribution and supply.
At many places in the power system, it may be desirable and necessary to change
some characteristics e.g. voltage, ac to dc, frequency, power factor etc. of electric supply.
This accomplished by suitable apparatus called substation. For example; generation
voltage (11 KV or 33 KV) at the power station is set up to high voltage (say 220 KV or 132
KV) for transmission of electric power. The assembly of apparatus (e.g. transformer etc.)
used for this purpose in the substation. Similarly near the consumer’s localities the voltage
may have to be step down to utilization level. This job is again accomplished by suitable
apparatus called substation. The assembly of apparatus to change some characteristic of
electric power supply is called substation.
Figure 1 View of sub-station
About 132/33kv minto park sub-station
Figure 2 High voltage and low voltage transmission side
The sub-station gets its 132KV supply from the power grids located at 220kv S/S REWA
ROAD. At first a Lightning Assertor is used in a 3-phase transmission setup in order to
protect the grid from surges due to lightning. After this comes the need to measure the
voltage and current in the transmission lines. For that we use a Capacitor Voltage
Transformer and Current Transformer respectively. Just like an ammeter and a
voltmeter, a CT is connected in series with the transmission line whereas a CVT is
connected parallel to the transmission line. Since they both are transformer they must have
a transformation ratio.
Now comes the time of implementing some safety features in the transmission line
setup. For that we first use a Line Isolator and then a Bus Isolator. But these alone are not
enough, so we use a Gas Circuit Breaker. These circuit breakers can be operated via
control panel in the operating room.
Four transformers of 40MVA capacity each are installed in Minto Park sub-station,
thereby making a total station capacity of 160MVA. A lightning arrestor, current
transformer and some control equipment are used on both sides of the transformers for
better monitoring. The transformers step down the 132KV supply to 33KV supply. Then
this 33KV supply is fed to the sixteen feeders that are installed in the sub-station.
There is also a jack bus which is connected to the main bus with the help of a bus
coupler. It is used as a backup feeder when some other feeder is under maintenance. Also
there is another step down transformer installed in the sub-station which is used to supply
electricity to the sub-station.
ROUGH DESCRIPTION OFMINTO PARKSUB-STATION
INCOMING LINE VOLTAGE:
132kv incoming-1 from 220kv S/S Rewa Road
132kv incoming-1 from 220kv S/S Rewa Road
OUTGOING FEEDER VOLTAGE:
FOUR TRANSFORMER OF 40MVA ARE USED IN 132KV MINTO PARK SUB-STATION
As we know, MVA=√3VI
For 40 MVA,
40×106 = √3×132×103×I
I = 175A (HV)
40×106 = √3×33×103×I
I = 700A (LV)
Therefore, total transformer capacity = 4×40MVA= 160MVA
SINGLE LINE DIAGRAM :-
Figure 3 Single line diagram 132 kv minto park
A substation is a part of an electrical generation, transmission
and distribution system. Substations transform voltage from high
to low, or the reverse, or perform any of several other important
functions. Between the generating station and consumer, electric
power may flow through several substations at different voltage
levels. Substations may be owned and operated by an electrical
utility, or may be owned by a large industrial or commercial
customer. Generally substations are unattended, relying
on SCADA for remote supervision and control. A substation may
include transformers to change voltage levels between high
transmission voltages and lower distribution voltages, or at the
interconnection of two different transmission voltages.
Substations are classified by two broad categories:-
According to the service requirement:-
Power factor correction substation
Frequency change substation
According to the constructional features:
Pole mounted substation
They are known as transformer substations as because
transformer is the main component employed to change the
voltage level, depending upon the purposed served transformer
substations may be classified into:
a) STEP UP SUBSTATION
The generation voltage is steeped up to high voltage to
affect economy in transmission of electric power. These
are generally located in the power houses and are of
b) PRIMARY GRID SUBSTATION
Here, electric power is received by primary substation
which reduces the voltage level to 33KV for secondary
transmission. The primary grid substation is generally of
c) SECONDARY SUBSTATIONS
At a secondary substation, the voltage is further steeped
down to 11KV. The 11KV lines runs along the important
road of the city. The secondary substations are also of
d) DISTRIBUTION SUBSTATION
These substations are located near the consumer’s
localities and step down to 400V, 3-phase, 4-wire for
supplying to the consumers. The voltage between any
two phases is 400V & between any phase and neutral it is
1. Each circuit is protected by its own circuit breaker and hence
plant outage does not necessarily result in loss of supply.
2. A fault on the feeder or transformer circuit breaker causes loss
of the transformer and feeder circuit, one of which may be
restored after isolating the faulty circuit breaker.
3. A fault on the bus section circuit breaker causes complete
shutdown of the substation. All circuits may be restored after
isolating the faulty circuit breaker.
4. Maintenance of a feeder or transformer circuit breaker
involves loss of the circuit.
5. Introduction of bypass isolators between bus bar and circuit
isolator allows circuit breaker maintenance facilities without
loss of that circuit.
STEPS IN DESIGNING SUBSTATION :-
The First Step in designing a Substation is to design an Earthing and
Earthing and Bonding:-
The function of an earthing and bonding system is to provide
an earthing system connection to which transformer neutrals or
earthing impedances may be connected in order to pass the
maximum fault current. The earthing system also ensures that
no thermal or mechanical damage occurs on the equipment
within the substation, thereby resulting in safety to operation
and maintenance personnel. The earthing system also
guarantees equipotent bonding such that there are no
dangerous potential gradients developed in the substation.
In designing the substation, three voltages have to be
considered these are:
1. Touch Voltage
This is the difference in potential between the surface
potential and the potential at earthed equipment whilst
a man is standing and touching the earthed structure.
2. Step Voltage
This is the potential difference developed when a man
bridges a distance of 1m with his feet while not touching
any other earthed equipment.
3. Mesh Voltage
This is the maximum touch voltage that is developed in
the mesh of the earthing grid.
Calculations for earth impedances, touch and step potentials are
based on site measurements of ground resistivity and system fault
levels. A grid layout with particular conductors is then analyzed to
determine the effective substation earthing resistance, from which
the earthing voltage is calculated.
In practice, it is normal to take the highest fault level for substation
earth grid calculation purposes. Additionally, it is necessary to
ensure a sufficient margin such that expansion of the system is
To determine the earth resistivity, probe tests are carried out on the
site. These tests are best performed in dry weather such that
conservative resistivity readings are obtained.
Earthing Materials :-
Bare copper conductor is usually used for the substation earthing
grid. The copper bars themselves usually have a cross-sectional area
of 95 square millimeters, and they are laid at a shallow depth of
0.25-0.5m, in 3-7m squares. In addition to the buried potential earth
grid, a separate above ground earthing ring is usually provided, to
which all metallic substation plant is bonded.
Connections to the grid and other earthing joints should not be
soldered because the heat generated during fault conditions could
cause a soldered joint to fail. Joints are usually bolted.
3. Earthing Rods
The earthing grid must be supplemented by earthing rods to assist in
the dissipation of earth fault currents and further reduce the overall
substation earthing resistance. These rods are usually made of solid
copper, or copper clad steel.
Switchyard Fence Earthing
The switchyard fence earthing practices are possible and are used by
different utilities. These are:
a) Extend the substation earth grid 0.5m-1.5m beyond the fence
perimeter. The fence is then bonded to the grid at regular
b) Place the fence beyond the perimeter of the switchyard
earthing grid and bond the fence to its own earthing rod
system. This earthing rod system is not coupled to the main
substation earthing grid.
An ideal conductor should fulfill the following requirements:
a) Should be capable of carrying the specified load currents and
short time currents.
b) Should be able to withstand forces on it due to its situation.
These forces comprise self-weight, and weight of other
conductors and equipment, short circuit forces and atmospheric
forces such as wind and ice loading.
c) Should be corona free at rated voltage.
d) Should have the minimum number of joints.
e) Should need the minimum number of supporting insulators.
f) Should be economical.
The most suitable material for the conductor system is copper or
aluminums. Steel may be used but has limitations of poor
conductivity and high susceptibility to corrosion.
In an effort to make the conductor ideal, three different types have
been utilized, and these include: Flat surfaced Conductors, Stranded
Conductors, and Tubular Conductors.
Two methodsare used to terminate overheadlines at a substation.
a) Tensioning conductors to substation structures or buildings
b) Tensioning conductors to ground winches.
The choice is influenced by the height of towers and the proximity
to the substation.
The following clearances should be observed:
VOLTAGE LEVEL MINIMUM GROUND CLEARANCE
less than 11kV 6.1m
11kV - 20kV 6.4m
20kV - 30kV 6.7m
STANDARD SIZES OF CONDUCTOR FOR LINES OF VARIOUS VOLTAGES
The following sizeshave now been standardized by CEA for transmission lines of different
1. For 440 KV Lines
Twin 'Moose' ACSR having 7-Strands of steel of dia 3.53 mm
and 54-Strands of Aluminum of dia 3.53 mm.
2. For 220 KV Lines
'Zebra' ACSR having 7-strand of steel of dia 3.18 mm and 54-
Strands of Aluminum of dia 3.18 mm.
3.For132 KV Lines
'Panther' ACSR having 7-strands of steel of dia 3.00 mm and
30-Strands of Aluminum of dia 3.00 mm.
Clearance in accordance with voltage value
-: ISOLATOR :-
Mainly the isolator is connected after the circuit breaker .The
circuit breaker is trip due to the fault, or when suddenly a
heavy current is flows , it means that the current will not flow
after the breaker ,but small amount of current is flows inner
For making this current total zero the isolator is open and
isolator is connected to ground so all inner current will
grounded. This is the main work of isolator and other
equipments are saved.
Isolatorsare two types :-
1- Bus Isolator- the isolator is directly connected with main
2- Line Isolator- the isolator is situated at line side of any
-: INSULATOR :-
The insulator serve two purpose. They support the conductor
(bus bar ) and confine the current to the conductor . The most
commonly used material for the manufacturerof insulatoris
But the most wild use of insulatoris to insulate the support or
from the electric current .These are several type of insulators
(e.g. pin type ,suspension type , post insulator ,shackle
insulator etc.) and their use in the substation will depend upon
the service requirement .For example post insulator is used for
bus bars can directly bolted to the cap.
-: TRANSFORMER :-
A transformer is an electrical device that
transfers energy betweentwo ormore circuits
Step Up Transformer
Step Down Transformer
Its primary and secondary winding resistances
are negligible .
Its leakage flux and leakage inductanceare zero
There are no losses due to resistance, hysteresis
and eddy currents.
The efficiency is 100 percent.
In case ofideal transformer Np*Ip =Ns*Is
PROTECTION OF TRANFORMER :-
As the temperature of oil increases or decreases during
operation there is corresponding rise or fall in volume. To
account for this an expansion vessel is connected to the
The conservator has got a capacity between minimum and
maximum oil level equal to 10% of the total oilin
The conservator is provided with magnetic oil level gauge on
one of the end covers which has a low oil level alarm. The ideal
indicates empty 1/4,30.c, ¾ and fulloillevel.
Owing the transport limitation and considering possible
transient damages. Large transformer are provided with
detachable radiators with radiator value.
At the time of dispatch these radiators are detach and sent
separately keeping the valve in positionon tank flange. The
valve blanking plate is to removed only when the radiators is
ready formounting onflanges. On removal ofblanking plate a
small quantity ofoilwhich may have collected between valve
and blanking platewillseep out.
The radiator section is made of 1mm thick cold rolled carbon
steel sheets. The distance between each section is 50mm.
The number of section per radiators and the number of
radiators per transformer will depend upon cooling
requirement of that transformer.
BUCHHOLZ RELAY :-
The transformer is fitted with double
float buchholz relay.
It is fitted in the feed pipe from conservator to tank and it is
provided with two sets of mercury contacts.
The device comprises with the cast iron housing containing the
hinged floats, one in upper part and other in lower part . Each
float is fitted with mercury switches, leads of which are
connected to terminal box for external connection.
An arrow in cast on the housing to indicate the direction of
conservator. The operation of buchholz relay should be tested
before installing by injecting air at the lowest cock.
It is connected to the protection circuit to give an early alarm
in case of gas collection and to disconnection of transformer
from supply in case the sever fault inside the transformer.
SILICA GEL BREATHER :-
When transformer is loaded or unloaded the oil
temperature inside the transformer is rise or falls.
Accordingly the volume of air is changes by either by
sucking in or pushing out . This transformer phenomena
is called BREATHING of transformer.
The air which I being sucked in container may have foreign
impurities and humidity which changes dielectric stray of
transformer oil . Hence it is necessary that the air entering into
the transformer is free room moisture and foreign impurities.
The breather is connected to an outlet pipe of conservator
vessel and the air which is sucked by the transformer is made
to pass through silica gel breather to dehumidify the air and
remove the foreign impurities . The air which is pass through
the gel is pass first to oil compartment of the breather. The oil
removes all foreign impurities which enter into the gel
compartment. Silica gel breather keeps all the properties of oil
constant so transformer has a long life.
When a transformer is in operation the heat is generated
due to iron loss in winding and core loss. The process of
minimise this heat is called cooling.
AIR NATURAL COOLING :-
In a dry type self-cooled transformer, the natural circulationof
surrounding air is used for cooling. This process of cooling is
satisfactory for low voltage small transformer up to few KVA.
AIR BLAST COOLING :-
It is similar to natural cooling with an addition that continuous
blast of filtered cooled air is forced through the core and
winding for better cooling. A fan producesthe blast.
ForcedOil withCirculatingWaterCooling :-
In this type of system heat exchanger is used for cooling the
transformer . This system is used for large rating of power
Wave trap unit is inserted between bus bar and connection of
coupling capacitor to the line. It is parrel tuned circuit
comprising L and C. It has low impedance to 50 Hz and high
impedance to carrier frequencies.
Thus coupling capacitor allows carrier frequencies signals to
enter the carrier equipment, but does not allows 50Hz power
frequency current to enter the carrier equipment. This unit
prevents the high frequencies signal from entering the
neighbouring line, and the carrier current to flow only in the
protected line for communication between different substation.
LIGHTING ARRESTER :-
Lighting arresters are protective device for limiting surge
voltages due to lighting strikes or equipment faults or other
events, to prevent damage to equipment and disruption of
service. This type of equipment also called surge arresters.
Lighting arresters are installed on many different pieces of
equipment such as power poles and towers, power
transformer, circuit breaker, bus structure, and steel
A current transformer (CT) is used for measurement of
alternating electric currents. Current transformers, together
with voltage (or potential) transformers (VT or PT), are known
as instrument transformers. When current in a circuit is too
high to apply directly to measuring instruments, a current
transformer produces a reduced current accurately proportional
to the current in the circuit, which can be conveniently
connected to measuring and recording instruments. A current
transformer isolates the measuring instruments from what may
be very high voltage in the monitored circuit. Current
transformers are commonly used in metering and protective
relays in the electrical power industry.
They are commonly used in metering and protective
relaying in the electrical power industry where they
facilitate the safe measurement of large currents, often in
the presence of high voltages.
The current transformer safely isolates measurement and
control circuitry from high voltage typically present on the
circuit being measured. The CT acts as constant current
series device with an apparent power burden a fraction of
that of high voltage primary circuit.
Common secondary's are 1 or 5 amperes . For example; a
400:1 CT would provide an output current of 1 ampere
when the primary was passing 400 amperes.
Current transformers used in metering equipment for
three-phase 400-ampere electricity supply
Like any other transformer, a current transformer has a
primary winding, a magnetic core and a secondary
winding. The alternating current in the primary produces
an alternating magnetic field in the core, which then
induces an alternating current in the secondary winding
circuit. An essential objective of current transformer design
is to ensure the primary and secondary circuits are
efficiently coupled, so the secondary current is linearly
proportional to the primary current.
The most common design of CT consists of a length of
wire wrapped many times around a silicon steel ring
passed 'around' the circuit being measured. The CT's
primary circuit therefore consists of a single 'turn' of
conductor, with a secondary of many tens or hundreds of
turns. The primary winding may be a permanent part of the
current transformer, with a heavy copper bar to carry
current through the magnetic core. Window-type current
transformers (aka zero sequence current transformers, or
ZSCT) are also common, which can have circuit cables run
through the middle of an opening in the core to provide a
single-turn primary winding. When conductors passing
through a CT are not centered in the circular (or oval)
opening, slight inaccuracies may occur.
A voltage transformer theory or potential transformer
theory is just like a theory of general purpose step down
transformer. Primary of this transformer is connected across
the phase and ground. Just like the transformer used for
stepping down purpose, potential transformer i.e. PT has lower
turns winding at its secondary. The system voltage is applied
across the terminals of primary winding of that transformer,
and then proportionate secondary voltage appears across the
secondary terminals of the PT.
The secondary voltage of the PT is generally 110 V. In an ideal
potential transformer or voltage transformer, when rated
burden gets connected across the secondary; the ratio of
primary and secondary voltages of transformer is equal to the
turns ratio and furthermore, the two terminal voltages are in
precise phase opposite to each other. But in actual transformer,
there must be an error in the voltage ratio as well as in the
phase angle between primary and secondary voltages.
Potential transformer is designed for monitoring single - phase
and three - phase line voltages in power metering application.
The primary terminals can be connected either in line - to -line
or in line - to - neutral configuration.
A potential Transformer is a special type of transformer that
allows meters to take reading from electrical service
connections with higher voltage than the meter is normally
capable of handling without at potential transformer .
Potential transformer has an accuracy of +_ 5% from 0 to
130% of their rated voltage.
Circuit breaker is mechanical device which is so designed by
which circuit normal current fault position will be on and off
.They are used for high capacity. A circuit breaker can make
or break a circuit either manually or automatically under all
condition viz. no load and short circuit condition .
Typesofcircuitbreaker is :-
Oil circuit breaker:
In oil circuit breaker the fixed contact and moving contact are
immerged inside the insulating oil. Whenever there is a separation of
electric current carrying contacts in the oil, the arc in circuit breaker is
initialized at the moment of separation of contacts, and due to this arc
the oil is vaporized and decomposed in mostly hydrogen gas and
ultimately creates a hydrogen bubble around the arc. This highly
compressed gas bubble around the arc prevents re-striking of the arc
after electric current reaches zero crossing of the cycle.
AIR CIRCUIT BREAKER :
For interrupting arc it creates an arc voltage in excess of the
supply voltage. Arc voltage is defined as the
minimum voltage required maintaining the arc. This circuit
breaker increases the arc voltage by mainly three different
It may increase the arc voltage by cooling the arc plasma. As
the temperature of arc plasma is decreased, the mobility of the
particle in arc plasma is reduced, hence more voltage gradient
is required to maintain the arc.
It may increase the arc voltage by lengthening the arc path. As
the length of arc path is increased, the resistance of the path is
increased, and hence to maintain the same arc electric
current more voltage is required to be applied across the arc
path. That means arc voltage is increased.
Splitting up the arc into a number of series arcs also increases
the arc voltage.
Sulphur Hexa Fluoride circuit breaker :
In such circuit breaker, sulphur hexafluoride (SF6) gas is used
as the arc quenching medium. The SF6 is an electronegative
gas and has a strong tendency to absorb free electrons.
It consists of fixed and moving contacts. It has chamber,
contains SF6 gas. When the contacts are opened, the
mechanism permits a high pressure SF6 gas from reservoir to
flow towards the arc interruption chamber. The moving
contact permits the SF6 gas to let through these holes.
These circuit breakers are availabl for the voltage ranges from
33KV to 800KV and even more.
Vacuum circuit breaker :
Vacuum circuit breakers are circuit breakers which are used to
protect medium and high voltage circuits from dangerous
electrical situations. Like other types of circuit breakers,
vacuum circuit breakers literally break the circuit so that
energy cannot continue flowing through it, thereby preventing
fires, power surges, and other problems which may emerge.
The operation of opening and closing of electric current
carrying contacts and associated arc interruption take place in
a vacuum chamber in the breaker which is called vacuum
This is the main part of the substation. We plant it outside the switchyard. All the
equipment which is install inside the switchyard is connected to the control panel
by a underground cable. These cable are connected to the measuring devices like
as voltmeter and ammeter of high rating.
This control panel also consists a different type of relays like
as differential, earth fault, auxiliary etc. control panel gives all
the correct reading for example when a line is come in switch
yard is connected to CVT. This CVT gives an exact value of
incoming voltage on the control panel, If any fault is occurs,
the relay is trip and we can see it on control panel and except it
control panel gives the rating of all feeders and temperature of
oil and winding in the transformer.
This is the room, which consist DC batteries. There are 55 DC
cell of 2 Volt each. These cells are connected in series, so it
will give total of 110V. This 110VDC Supply is used for
operating the controlpanel, when the AC supply is off. This
110V DC voltage is also supplied to circuit breakers for
operating; this supply is used when AC is off. We use this
supply as a secondary supply. It means that this DC voltage is
used when the AC is interrupted.
-: CONCLUSION :-
Now from this report one can conclude that electricity plays an
important role in our life. At the end of the training, I came to
know about the various parts of substations and how they are
operated. Also I learnt about how transmission is done in
various parts of Uttarpradesh.
As evident from the report, a substation plays a very important
role in the transmission system. That’s why various protective
measures are taken to protect the substations from various
faults and its smooth functioning. Power Transmission
Corporation of Uttarpradesh Limited takes such steps so
that a uniform and stable supply of electricity can reach in
every part of this state.
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