Study of switchyard and transformer

1. A
INDUSTRIAL TRAINING PROJECT REPORT
ON
Study of SWITCHYARD AND
TRANSFORMER
At
Under Guidance of:-
1. KAMALESH KUMAR (DEPUTY MANAGER)
2. ASIMA CHANDRA (ASSISTANT MANAGER)
Submitted in partial fulfillment of the requirement
For the award of degree
Of
B-TECH
SESSION (2017-2018)
SUBMITTED TO: - SUBMITTED BY:-
KBUNL/NTPC, KANTI. NEERAJ PRASAD
Muzaffarpur, Bihar ELECTRICAL Engineering
University Roll No -
SURENDRA INSTITUTE OF ENGINEERING AND MANAGEMENT, SILIGURI

2. Certificate
This is to certified that Mr.NEERAJ PRASAD. Roll number --------
student of 2014-2018 batch of Electrical Engineering 7th semester of
Surendra Institute Of Engineering And Management, Siliguri
has successfully completed his industrial training at Kanti Thermal
Power Station (a joint venture of NTPC Ltd. and BSEB) Muzaffarpur
for one month from 03/07/2017 to 02/08/2017.
He has completed the whole training as per schedule.

3. ACKNOWLEDGEMENT
It is my pleasure to be indebted to various people, who directly or
indirectly contributed in the development of this work and who influenced my
thinking, behavior, and acts during the course of study.
I express my sincere gratitude to Mr. SANJEEV KUMAR(DY. MANAGER) ,
for providing me an opportunity to undergo summer training at NTPC-KBUNL,
Muzaffarpur.
I am thankful to Mr. KAMALESH KUMAR for his support, cooperation, and
motivation provided to me during the training for constant inspiration, presence
and blessings.
I also extend my sincere appreciation to MS.ASIMA CHANDRA
who provided her valuable suggestions and precious time in accomplishing my
project report.
Lastly, I would like to thank the almighty and my parents for their
moral support and my friends with whom I shared my day-to-day experience and
received lots of suggestions that improved my quality of work.
Submitted by :
NEERAJ PRASAD
B.TECH (Electrical Engineering)
6th sem, Roll:- ----------------------
SIEM, Siliguri

4. ABSTRACT
Any thermal power plant is converting the chemical energy of fossil
Fuel (coal) into electrical energy. The process involved for this
conversion is based upon the Modified Rankin cycle is
 Boiler feed pump,
 The steam generator water walls (evaporator),
 Steam generator super heater,
 Steam turbine,
 Reheater,
 Condenser
 Regenerative feed heaters etc.
All component of power generating cycle are vital and critical in
operations in modified Rankin cycles, the two most important aspects
that is added are reheating & regenerative heating. By reheating we used
to send the steam coming from exhaust of the turbine back to the reheat
of the boiler so that its enthalpy increases and more work can be done by
this steam and other purpose is to make steam dry so that no harm will
be done to the blades of the turbine
In NTPC Kanti, we have three turbines in Tandem coupling namely one
H.P Turbine, one I.P Turbine & one L.P Turbine coupled with the
generator to which is synchronized with the grid to produce electricity at
50Hz
In all my modesty, I wish to record here that a sincere attempt has been
made for the presentation of this project report. I also trust that this study
will not only prove to be a academic interest but also will be able to
provide an insight into the area of technical management.

5. CONTENTS
Transformer
 Working principle of transformer
 Classification of transformer
 Transformer accessories
 Heat generation in transformer
 Cooling of transformer
 Transformers use in KBUN
 Losses of transformer
Switchyard
• Working of switchyard
• Components of switchyard

6. TRANSFORMER:-
Electrical power transformer is a static device which transforms electrical energy
from one circuit to another without any direct electrical connection and with the
help of mutual induction between two windings. It transforms power from one
circuit to another without changing its frequency but may be in different voltage
level.
Working Principle of Transformer
The working principle of transformer is very simple. It depends upon
Faraday's law of electromagnetic induction. Actually, mutual induction
between two or more winding is responsible for transformation action in
an electrical transformer.
Faraday'sLaws of ElectromagneticInduction:-
According to these Faraday's laws ,"Rate of change of flux linkage with respect
totime is directly proportional to the inducedEMF in a conductoror coil".
The transformers used in a power station have its sides abbreviated as Low
Voltage (LV) and High Voltage (HV) rather than primary and secondary.

7. E.M.F EQUATION:-
Let Ø = Ømax sin ωt
The instantaneous induced e.m.f in a ‘N’ turn coil is
e = - N dØ/dt = - ω Ømax N cos ωt ……... (1)
The max.value of induced e.m.f is
Emax = 2 Π f Ømax N Volts …………..…….... (2)
The E.M.F equation is Erms = 4.44 Ømax f N … (3)
If primary has N1 no. of turns, then
E1 = 4.44 Ømax f N1
If the secondary has N2 number of turns, then
E2 = 4.44 Ømax f N2
Voltage per turn is same for primary as well as secondary windings. i.e.,
E1/N1 = E2/N2 4.44 Ømax f
& the transformation ratio is defined as
K = E2/E1 = N2/N1 = I1/I2
VOLTAGE REGULATION:-
The voltage regulation is the percentage of voltage difference between
no load and full load voltages of a transformer with respect to its full
load voltage.
Explanation:-
Let an electrical power transformer is open circuited, means load is not
connected with secondary terminals. So, the secondary terminal voltage of
the transformer will be its secondary induced emf E2. Whenever full load is
connected to the secondary terminals of the transformer, rated current I2
flows through the secondary circuit and voltage drop comes into picture. At
this situation, primary winding will also draw equivalent full load current
from source. The voltage drop in the secondary is I2Z2 where Z2 is the
secondary impedance of transformer.Now if at this loading condition, if
wemeasures the voltage between secondary terminals, we will get voltage
V2 across load terminals which is obviously less than no load secondary
voltage E2 and this is because of I2Z2 voltage drop in the transformer.
Hence voltage regulation = [(E2 – V2)/V2] *100

8. STEP UP/STEP DOWN TRANSFORMER:-
If K>1, then E2>E1; This transformer is called as step-up transformer.
If K<1, then E2<E1; This transformer is called as step-down
transformer.
If K=1, then E2=E1; This transformer is known as isolation transformer.
It merely isolates two electric circuits
Classification of transformer:-
Depending on Type of Applications transformers are classified as Power
transformers and Distribution transformers.
1.2.2 Depending on No. of Phase transformers are classified as Single
phase and Three Phase transformers.
1. Depending on Type of Construction transformers are classified as
Core type and Shell type.
2. Depending on Type of Winding transformers are classified as Two
winding and Three winding. Two Winding Transformer has One HV &
One LV Windings eg. Generator Transformer.Three Winding
Transformer has One HV & Two LV Windings eg. UAT/RAT/CSAT
3. Depending on application transformers are classified as Instrument
Transformers i.e. CT/VT.
1. Core type: Where windings surrounds the core.
2. Shell type: Where core surrounds the windings.
Core type transformer:
a. It has two legs ( also called as limbs ).
b. Each winding is divided into four equal parts.
c. L.V winding is placed next to the core.
d. H.V winding is placed next to the L.V winding.
e. One-half of the windings is placed on one limb & the other half is on
the other limb.

9. SHELL TYPE TRANSFORMER
a.The L.V & H.V coils are wound on the central limb and they are
interleaved or sandwiched.
b. It requires more conducting material than core type of transformer.
c. It has two magnetic paths & the flux through the each path is half of
the total flux ( ).
d. It provides shorter magnetic path and hence magnetizing current is
lesser than in the core type transformer.
e. The horizontal portion of magnetic core is called as yoke
Transformer accessories:
1. Core-Cores are manufactured of High quality cold-rolled grain oriented
silicon steel laminations of ~0.33 mm thickness. Silicon steel raises the
permeability of the material at low flux densities & thereby reduces the
hysteresis & eddycurrent losses. Core sheets are laminated into sections to
reduce the iron losses.
2.Conservator: With the variation of temperature there is
corresponding variation in the oil volume. To account for
this an expansion vessel called conservator is added to the
transformer with a connecting pipe to the main tank. It is
also used to store the oil and makeup of the oil in case of
leakage.
3.Breather: In conservator the moisture from the oil is
excluded from the oil through breather it is a silica gel
column, which absorbs the moisture in air before it enters
the conservator air surface.

10. 4.Radiator: This a chamber connected to the transformer
to provide cooling of the oil. It has got fans attached to
it to provide better cooling.
5.Bushing:Bushings comprises of central conductor
surrounded by graded insulation.Bushing is necessary
whenever conductor is taken out through transformer tank.
Simple porcelain insulator bushing are generally used up to
20 kV class. Oil filled bushings are used for 33 kV and above
applications. For making bushing compact, synthetic resin
bonded condensor bushing are used for HV transformers.
Condensor bushing consists of a central conductor surrounded
by alternate layers of insulating papers and tin foils,
capacitance formed due to this results in uniform stress
distribution between conductor surface and earthed flanges
6. Tap Changer: Tap changer is used to vary output voltage
in within designed limit. The objective of Tap Changer is for
adjusting secondary voltage incase of primary voltage
variation.Tap changers are classified as off load and on load
tap changer. On load tap changer is generally located in the
HV side of the winding due to low current, finer control. HV
winding terminals are located outside &Hence easy to take
the tapping terminals out
Heat Generation in transformer:-
The main source of heat generation in transformer is its copper
loss or I2R loss. Although there are other factors contribute heat
in transformer such as hysteresis & eddy current losses but

11. contribution of I2R loss dominate them. If this heat is not
dissipated properly, the temperature of the transformer will rise
continually which may cause damages in paper insulation and
liquid insulation medium of transformer. So it is essential to
control the temperature with in permissible limit to ensure the
long life of transformer by reducing thermal degradation of its
insulation system. In electrical power transformer we use
external transformer cooling system to accelerate the dissipation
rate of heat of transformer.
Cooling of transformer:
The primary material that is uses for cooling purpose is Oil because it
works for both cooling and insulation.
1.Cooling: Provides a better cooling and helps in exchanging heat .
2. Insulation: A non conductor of electricity so good insulator. The
oil used is such that its flash point is pretty high so that it doesn’t
have any possibility to catch fire.
Insulating oil
It is normally obtained by fractional distillation and subsequent treatment of crude
petroleum. That is why this oil is also known as mineral insulating oil.
Type of Oil:-
Generally there are two types of transformer Oil used in transformer,
1. Paraffin based transformer oil
2. Naphtha based transformer oil
There are different transformer cooling methods available for
transformer:-
1. AN – Air Natural
2. ON – Oil Natural
3. AF – Air forced
4. OF – Oil forced
5. ONAF – Oil natural Air forced
6. OFAN - Oil forced Air natural
7. OFAF – Oil forced Air forced

12. The oil serves as the medium for transferring the heat
produced inside the transformer to the outside transformer.
Thermo siphon action refers to the circulating currents set
up in a liquid because of temperature difference between
one part of the container and other. When oil gets heated
up the oil with greater temp, goes to the upper side of the
transformer. Now if it is Oil natural it is cooled in it as it
is whereas in Oil Forced a radiator is being constructed
and a pump is being attached to it to pull the oil from the
upper part of the transformer. Now this oil in the chamber
gets cooled either by direct heat exchanging through the
atmosphere which is called Air Natural or by forced air draft
cooling by a radiator with many electric fans which are
automatically switched on and off depending upon the
loading of transformer which is known as Air Forced cooling.
As the oil gets cooled it becomes heavier and sinks to the bottom.
Cooling System For Power Transformers of KBUNL
Project:-
ONAF Cooling :Transformers with ONAF cooling system (type D)
must be equipped with the control panel for Automatic start up
and shut down of the electrical fan motors. Fans must be
switched when the temperature of upper oil layers
reachesapproximately 55º C or when the rated current is reached
in dependent of the temperature.
Fans must be switched off when the oil temperature is decreased
to 50º C and the load current is less than rated value. Fan may
start even in case transformers load is more than 50% of nominal
value
OFAF Cooling: OFAF cooling transformers with OFAF cooling
must be equipped with the control panels for performing the
following function.
• Automatic startup of the cooling system simultaneously with
the energisation of transformers. This start up is performed by
groups and coolers depending on transformers load.
• Automatic switching off the cooling system when the
transformer is disconnected.
• Manually operated control for each cooler.

13. Transformer use in KBUNL project:-
1. 220/132 KV Inter Connecting Transformer (ICT)
2. 11/6.6KV Unit Auxiliary Transformer (UAT)
3 220 / 6.6KV Station Transformer (ST)
4. 11KV / 220 KV Generator Transformer (GT)
5.Current Transformer (CT)
6. Voltage Transformer Or Potential Transformer (PT)
7. Neutral Grounding Transformer (NGT)

14. 1. Inter Connecting Transformer (ICT):-
Inter connecting Auto Transformer serves as the link between the 132
KV and 220 KV switch yard. They have been designed as three phase
with a capability of 100 MVA.
Specification:-
2. Unit Auxiliary Transformer:-
The Unit Auxiliary Transformer is the Power Transformer that provides
power to the auxiliary equipment of a power generating station during its
Type of Cooling O
FA
F
ON
AN
MAKERS SERIAL
NO.
600446
MVA Rating HV & LV 10
0
50 ELECTRICAL SPEC
NO.
600580
TV 30 15 YEAR OF
MANUFACTURE
1982
KILO VOLTS NO LOAD
HV
22
0
220 DIAGRAM DRG.
NO.
1462190
013
LV 13
2
132 INSULATION
LEVEL
TV 33 33 HV 900KVp
LINE AMPERES HV 26
2.4
131.
2
HV(N) 38KV
RMS
LV 43
7.4
218.
2
LV 550KVp
TV 52
5
262.
5
TV 170KVp
IMPEDENANCE VOLTS %
(AT 100 MVA BASE)
CORE & WINDING
Kg
68335
HV-LV 9.68 WEIGHT OF OIL
Kg
39515
HV-TV 35.40 TOTAL WEIGHT
Kg
145840
LV-TV 23.55 OIL QUANTITY
LITRES
45420
PHASES 3 TRANSPORT
WEIGHT Kg
83340
FREQUENCY HZ 50 UNTANKING
WEIGHT Kg
68335
VECTOR SYMBOL HV-
LV
YNd0
HV-TV Yd11

15. normal operation. This transformer is connected directly to the generator
out-put by a tap-off of the isolated phase bus duct and thus becomes
cheapest source of power to the generating station.
It is generally a three-winding transformer i.e. one primary and two
separate secondary windings. Primary winding of UAT is equal to the
main generator voltage rating. The secondary windings can have same or
different voltages
At each unit three phase unit auxiliary transformer (two in each unit) are
designed for operation with capacity of 2 x 20 MVA voltage ratio 11/6.6
KV with two low voltage windings.
The capacity of UAT based on the following factor:-
• Total power required for units auxiliaries.
• Provision of self-start of the motors in case of short-term reduction
in voltage.
Specification:-
Temperature Rise Oil 50ºC Winding 55ºC
Type of Cooling ONAN MAKERS SERIAL NO. 600445
MVA Rating 20 ELECTRICAL SPEC
NO.
600578A
YEAR OF
MANUFACTURE
1981
KILO VOLTS NO LOAD HV 11 DIAGRAM DRG. NO. 14561900037
LV 7 INSULATION LEVEL
HV 75KVp
LINE AMPERES HV 1049.8 LV 60KVp
LV 1649.6
IMPEDENANCE VOLTS % 9.58 CORE & WINDING Kg 19300
PHASES 3 WEIGHT OF OIL Kg 10858
FREQUENCY HZ 50 TOTAL WEIGHT Kg 51135
VECTOR SYMBOL Dd0 OIL QUANTITY
LITRES
12480
PHASES 3
HV TERMINALS 2U, 2V, 2W LV TERMINALS 1U,
1V, 1W
%
IMPEDENCE
SWITCH LEADS HV KV HV AMP LV KV LV AMP

16. POSITION CONNECTED
1 20 - 19 12.10 954.33
2 20 - 18 11.96 965.50
3 20 - 17 11.83 975.11
4 20 - 16 11.69 987.80
5 20 - 15 11.55 999.77
6 20 - 14 11.41 1012.04
7 20 - 13 11.28 1023.70
8 20 - 12 11.14 1036.57
9 20 - 11 11.00
NOR
1049.76 7.00 1649.62
10 20 - 10 10.86 1063.29
11 20 - 9 10.73 1076.17
12 20 - 8 10.59 1090.40
13 20 - 7 10.45 1105.00
14 20 - 6 10.31 1120.01
15 20 - 5 10.18 1134.32
16 20 - 4 10.04 1150.13
17 20 - 3 9.90 116.406
Protection Of UAT:-
1. Transformer gas protection- through Buchholz Relay . This relay operates
with an alarm signal in the first stage and in the tripping stage, it operates
without time delay for opening the 220kV power unit circuit breakers and
activation of the 220 kV circuit breakers failure protections, and for opening
the GCB, field circuit breaker (generator de-excitation), turbine shut down
and for opening the 6.6 kV circuit breakers at the working auxiliary power
supply inputs to the both 6.6 kV bus;
2. OLTC gas protection – through Buchholz Relay . This relay operates
without time delay for opening the 220 kV power unit circuit breakers and
activation of the 220 kV circuit breakers failure protections, and for opening
the GCB, field circuit breaker (generator de-excitation), turbine shut down
and for opening the 6.6 kV circuit breakers at the working auxiliary power
supply inputs to the both 6.6 kV bus;
3. over current detection in the 6.6 kV network (51UAT). It is installed in the HV
windings of the transformer for opening the circuit breaker at the working auxiliary
power supply input to appropriate 6.6 kV bus, openingof the 220 kV power unit
circuit breakers, and activation of the 220 kV circuit breakers failure protections,

17. and for opening the GCB, field circuit breaker (generator de-excitation), turbine
shut down and for opening the circuit breakers at the working auxiliary power
supply inputs to the both 6 .6kV bus;
4. Winding and oil Temperature Indicator (WTI and OTI) operates in the first stage
for giving alarm signal and in the second stage - for opening 6.6 kV circuit
breakers at the working auxiliary power supply inputs to the both 6.6 kV bus.
Station Transformer:-
This type of transformer is used in sub stations to transfer the incoming voltage to
the next voltage level. It can be system or auto transformer with two/three
windings. In general it is equipped with On load tap changers and are connected to
transmission grids by bushings and cables.
Two station transformer is installed for two units and has been designed to supply
common station loads. Its capacity has been designed based on total common loads
of both the unit.
Station transformer are also connected to 6.6 KV buses of common station
auxiliary power supply system to use it as a stand by.
Specification:-
Name Plate Details of ST#1&2

18. Temperature Rise Oil 50ºC Winding 55ºC
Type of Cooling ONAN MAKERS SERIAL NO. 6004450
MVA Rating 31.5 ELECTRICAL SPEC NO. 600579
YEAR OF
MANUFACTURE
1983
KILO VOLTS NO LOAD HV 220 DIAGRAM DRG. NO. 14581900012
LV 7 INSULATION LEVEL
HV 900KVp
LINE AMPERES HV 82.67 HV NEUTRAL 38KV RMS
LV 2598.15 LV 60KVp
IMPEDENANCE VOLTS %
HV-LV
13.2 CORE & WINDING Kg 46413
PHASES 3 WEIGHT OF OIL Kg 35435
FREQUENCY HZ 50 TOTAL WEIGHT Kg 112985
VECTOR SYMBOL YNd11 OIL QUANTITY
LITRES
40730
PHASES 3 TRANSPORT WEIGHT Kg 90000
UNTANKING WEIGHT Kg 46413
HV TERMINALS 1U, 1V, 1W LV TERMINALS 2U,
2V, 2W
%
IMPEDENCE
SWITCH
POSITION
LEADS
CONNECTED
HV KV HVAMP LV KV LV AMP
1(MAX) 1N-12 3-4 247.5 73.48 11.62
2 1N-11 3-4 244.063 74.52
3 1N-10 3-4 240.625 75.58
4 1N-9 3-4 237.188 76.68
5 1N-8 3-4 233.750 77.81
6 1N-7 3-4 230.313 78.97
7 1N-6 3-4 226.875 80.16
8 1N-5 3-4 223.438 81.40
9a 1N-4 3-4 220.00 82.67
9b
(NORMAL)
1N-3↓ (3-4) (3-12)↑ 220.00 82.67 7.00 2598.15 13.2
9c 1N-12 3-12 220.00 82.67
10 1N-11 3-12 216.563 83.98
11 1N-10 3-12 213.125 85.34
12 1N-9 3-12 209.688 86.73
13 1N-8 3-12 206.250 88.18
14 1N-7 3-12 202.813 89.67
15 1N-6 3-12 199.375 91.22
16 1N-5 3-12 196.938 92.82
17 1N-4 3-12 192.500 94.48 15.75

19. Protection:-
1. Instantaneous over current protection (50 ) without time delay.
2. Differential protection (87T) for each reserve auxiliary transformer, without
time delay.
3. Restricted earth fault protection (87N) of 220 KV side without time delay.
4. Gas protection of the transformer without time delay .
5. On load tap changer (OLTC) gas protection without time delay.
6. Over load protection of each 6.6 KV winding (51) operating with time delay for
alarm.
7. Two earth fault protections against single phase short circuit in 6.6 KV network
(51 N) installed on the neutral of each 6.6 KV winding. The protections operates
with first time delay for opening 6.6 KV circuit breakers of corresponding input
and with the second time delay for opening 220 KV circuit breaker for opening
6.6 KV circuit breakers of the rest inputs to stand by supply trunk of both
transformers and for activating of 220 KV circuit breaker failure protection.
Generator Transformer:-
This is a type of Power Transformer where the LV winding is connected to the
generator through the bus duct and HV winding to the transmission system. In
addition to the features of Power Transformer, our Generator Transformer is
designed to withstand over voltage caused by suddenload throw off from the
generator. It is built as a single or three phase unit and located in power stations.
Generator transformer of each power unit consists of three single-phase
transformers with a power 2x140 MVA and voltage of 11/220 kV.

20. NAME PLATE DETAIL OF GT-1
TYPE OF COOLING OFAF ONAN
MVA RATING 140 70
KILO VOLTS NO LOAD
HV-230,LV-
11
HV-230,LV-
11
LINE AMPERES
HV-351.4A,
LV-7348.31A
PHASE 3
FREQUENCY 50HZ
VECTOR SYMBOL Ynd11
INSULATION LEVEL HV-900kvp
HV NEUTRAL 38KV RMS
LV 75 KVP
OIL QTY. 45060 Lit.
DATE OF SAMPLE 7/28/2011

21. Protection:-
1. Transformer differential and restricted ground fault protection (87T &
51GT). This relay operates without time delay for opening the 220 kV
circuit breakers and activation of the 220 kV circuit breakers failure
protections, opening the GCB, field circuit breaker (generator de-excitation),
turbine shut down and for opening the 6.6 kV circuit breakers at the working
auxiliary power supply inputs to the 6.6 kV bus;
2. Earth fault protection (51GT) This relay provides earth fault detection in the
generator transformer low voltage winding and the isolated phase bus ducts
in the event of GCB in open condition, and operates for opening the 220 kV
CB of the power unit and activation of the 220 kV circuit breakers failure
protections, opening the 6.6 kV CB of the working auxiliary power supply
inputs to the 6.6 kV bus;
3. Winding and oil temperature indicator (WTI and OTI) operates in the first
stage for giving alarm signal and in the second stage - for opening the 220
kV circuit breakers of the power unit and activation of the 220 kV circuit
breakers failure protections.
Current Transformer:-
Current transformers used in metering equipment for three-phase 400 ampere
electricity supply

22. A current transformer (CT) is a series connected measurement device designed to
provide a current in its secondarycoil proportional to the current flowing in its
primary. Current transformers are commonly used in metering and protective
relays in the electrical power industry.
Specification:-
HSV/NSV 245/220 Frequency 50 Hz
OIL 300 Kg
BIL 460/1050
TOTAL Wt. 1500 Kg
Voltage Transformer:-
Voltage transformers (VT), also called potential transformers (PT), are a parallel
connected type of instrument transformer, used for metering and protection in
high-voltage circuits or phasorphase shift isolation. They are designed to present
negligible load to the supply being measured and to have an accurate voltage ratio
to enable accurate metering. A potential transformer may have several secondary
windings on the same core as a primary winding, for use in different metering or
protection circuits. The primary may be connected phase to ground or phase to
phase. The secondaryis usually grounded on one terminal.
There are three primary types of voltage transformers (VT):
1. electromagnetic
2. capacitor
3. optical
1. The electromagnetic voltage transformer is a wire-wound transformer.
2. The capacitor voltage transformer uses a capacitance potential divider and is
used at higher voltages due to a lower costthan an electromagnetic VT.
3. An optical voltage transformer exploits the electrical properties of optical
materials. Measurement of high voltages is possible by the potential
transformers.

23. Neutral Grounding Transformer:-
Resistance grounding systems protectpower transformers and generators from
damaging fault currents. Low resistance grounding of the neutral limits the ground
fault current to a high level in order to operate protective fault clearing relays and
current transformers. These devices are then able to quickly clear the fault, usually
within a few seconds. Thelimited fault current and fast responsetime also prevent
over-heating and mechanical stress on conductors.
Name Plate Details of NGT OF ST#2
Temperature Rise Oil 50ºC Winding 55ºC
Type of Cooling ONAN MAKERS SERIAL
NO.
2262
KVA Rating 250 ELECTRICAL SPEC
NO.
DATE OF
MANUFACTURE
25.08.2011
KILO VOLTS NO LOAD
HV
6600 DIAGRAM DRG.
NO.
LV 240 INSULATION
LEVEL
HV
LINE AMPERES HV 21.8 LV
LV 601.4
IMPEDENANCE VOLTS % 5.14 CORE& WINDING
Kg
900
PHASES 3 WEIGHT OF OIL
Kg
450
FREQUENCY HZ 50 TOTAL WEIGHT
Kg
1900
VECTOR SYMBOL YNdiii OIL QUANTITY
LITRES
530
PHASES 3
Inter Bus Transformer:-

24. It is a kind of distribution transformer, who distribute the voltage produces bythe
plant by stepping down 220 kV/ 132 KV
Name Plate Details of IBT#1 & 2
Temperature Rise Oil 50ºC Winding 55ºC
Type of Cooling OFA
F
ONAN MAKERS SERIAL
NO.
600446
MVA Rating HV & LV 100 50 ELECTRICAL SPEC
NO.
600580
TV 30 15 YEAR OF
MANUFACTURE
1982
KILO VOLTS NO LOAD
HV
220 220 DIAGRAM DRG.
NO.
14621900
13
LV 132 132 INSULATION
LEVEL
TV 33 33 HV 900KVp
LINE AMPERES HV 262.4 131.2 HV(N) 38KV

25. RMS
LV 437.4 218.2 LV 550KVp
TV 525 262.5 TV 170KVp
IMPEDENANCE VOLTS %
(AT 100 MVA BASE)
CORE& WINDING
Kg
68335
HV-LV 9.68 WEIGHT OF OIL
Kg
39515
HV-TV 35.40 TOTAL WEIGHT
Kg
145840
LV-TV 23.55 OIL QUANTITY
LITRES
45420
PHASES 3 TRANSPORT
WEIGHT Kg
83340
FREQUENCY HZ 50 UNTANKING
WEIGHT Kg
68335
VECTOR SYMBOL HV-
LV
YNd0
HV-TV Yd11
Losses of Transformers:-
Losses in transformer consist of mainly two types No-load & on load losses.
1. No Load (Iron) Losses-Certain losses occur in a transformer regardless of
the load. When the unit is connected to a sourceof voltage. These loses
include corelosses, copperlosses in the primary winding due to the flow
of no-load current and electric losses in core. Eddy current loss due to
circulating currents in the core iron is also no-load loss.
2. Load (Copper)Losses-Load losses are those which occur in a
transformer during carrying of load. These losses are called copperlosses.
load losses are due to power lost when the load current flows through
the resistance of both the windings.

26.  Switchyard
Switchyard is the one of the most important sections of a power station
• It stabilises a link between power generation unit and power transmission unit.
• It is normally interconnected to all power grids and generation plants.
Working
• It transmits and receives the signal to/from grid control unit with the help of
microcontrollers.
• It is used for protection from short circuit, overloading, and under-loading
condition, by accidently or due to bad weather.
• The main function of a switchyard is to control the voltage and current and
to
distribute the power among sub-grids.
• It is also used for synchronizing the generating power and field power.

27. Components of a Switchyard
i. Voltage Transformers
ii. Current transformer
iii. Bus bar
iv. Lightening arrestor
v. Isolator
vi. Circuit breaker
vii. Wave trapper
viii. Earth switch
ix. Transmission tower

28.  TRANSFORMER
• Electrical machine which transforms the voltage from high voltage to Low voltage level
and vice-versa whereas maintains the same frequency and power at input and output
terminals
• It consists of core, primary winding, secondary winding for power transfer and oil for
cooling purpose
 Voltage Transformer
• To step-down (step-up) the high voltage to low voltage (low voltage to high
voltage)
 Current Transformer
• It measures current and auto adjust it to the required level
• It is a type of Auto-transformer

29.  BUS BAR
• Conductors to which a number of circuits are connected
 LIGHTNING ARRESTORS
• It is protecting device used to protect from high current flow in circuit due to
lighting
• It discharge high voltage to ground
• It is connected in all RYB-phase of supply

30.  ISOLATOR
• Isolator is a circuit breaker and circuit maker.
• It is used to open and close the bus connections.
• It helps to insure circuit connection from distance.
• It can operate manually or with the help of command from control room.
 CIRCUIT BREAKER
The protecting device to break the physical connections under fault conditions.
Main parts of circuit breaker
• Fixed Contact
• Movable Contact
• Operating Mechanism
• Arc extinguishing medium
Working
• When faults occurs high current may flow through circuits which is detected by
microcontrollers and hence send controlling signals to the “Relay”.
• Relay becomes activated and send command to the circuit breaker.
• Tripping coil of breaker gets activated and it trips or disconnects the connections.
• An arc may produce between the contacts and it is extinguished by the arc
extinguisher.
Types of Circuit Breaker
• Miniature Circuit Breakers
• Vacuum Circuit Breakers
• SF6 Circuit Breakers
• Air Blast Circuit Breakers
• Oil Circuit Breakers
Only SF6 and Vacuum Circuit Breakers are used at NTPC Kanti

31. Miniature Circuit Breakers (MCB)
Advantages
1. It is more sensitive than fuse
2. It can operate in upto 100A current
3. Less maintenance and
4. Low cost
Disadvantage
1.Not fully Automatic
Vacuum Circuit Breakers
Advantages
1. No need of oil or gases
2. Highly sensitive and self operating device

32. 3.Programmable and compact circuit
4. It can be use for high voltage
5. Low maintenance
Disadvantages
1. Bulky size
2. Loss of vacuum due to small damage
SF6 Circuit Breakers
• Sulphur Hexafluoride (SF6) gas is used in breaker medium.
• High pressure of gas extinguishes the arc produced in circuit and it also keeps
the breaker cool.
Advantages
1. Highly sensitive
2. Gas provide the insulation between contacts
3. It is used for high voltage
4. It has indicators to indicate pressure of gas
5. It can be used in outdoor
Disadvantages
1. High maintenance cost
2. Leakage of gas due to damage

33. Air Blast Circuit Breakers (ABCB)
Advantages
1. It is commonly used in day to day
life
2. Needs no oil or gas
3. It is used at atmospheric pressure
Disadvantages
1. It can not be used for high voltage
2. Oil circuit breaker is more
advantageous than ABCB

34. Oil Circuit Breakers
The mineral oil is used in oil circuit breaker. It is better insulating medium
than air. Highly compressed gas bubbles extinguish the arc.
Types of oil circuit breaker
1. Bulk Oil Circuit Breaker (BOCB)
2. Minimum Oil Circuit Breaker (MOCB)
Advantages
1. It is more sensitive
2. Widely used all over the country
Disadvantages
1. Needs high maintenance
2. Leakage of oil due to damage
Relay
• It is an important device of a switchyard
• Relay is an electrical switching device
• It works on electromagnetic principle
• It is connected between circuit breaker and microcontrollers
• It is highly sensitive and self operating device
• It can operate manually as well as automatically
• Circuit breaker is tripped on activation of relay
• Needs low maintenance

35. SCADA
• SCADA stands for “Supervisory Control and Data Acquisition”
• Supervisory - It means to monitor the data remotely
• Control – It means to control the data remotely
• Data Acquisition - It means to store the data to the system
• SCADA is widely used in industries
Working
• SCADA controls and monitor the devices and machines like motors, generators,
circuit breakers, oil tank level, gas leakage, etc. with the help of HMI (HumanMachine-
Interface) technology.
• Sensor detects the physical parameters from the machines and sents data to PLCs
(Programmable Logical Controls) which interface the data to the SCADA system
• Hence, command sent from control unit to the device and machines are remotely
controlled

36.  Control unit: NTPC Kanti
• The control unit having-
o SCADA display
o SCADA software installed systems
o Relay and microprocessor devices
o Controlling and protection panels of different units and areas
Relay and microprocessor devices

37. Controlling and protection panel
 Application of SCADA
It is used
• To insure the correctworking of machines in industry
• To remotely activate or deactivate the controllers to avoid hazards
• To control speed of motors, turbines, etc.
• To detect the leakages of gas, oil, or other fluid
 Advantages
1. Fault response time is very short
2. Isolate and precisely locate the faults
3. It can operate remotely
4. Less number of human source required
5. Display all the information separately on screen
 Disadvantage
1. Requires local area networking
2. On slightly mistake in operation it invites hazards
3. Requires power supply to each and every controllers continuously