Download Switch Yard Training Report NTPC Barh

B.K. Birla Institute of Engineering and Technology
Pilani-333031
Summer Internship
Repot for third year
Student Name : Praveen Kumar
Roll No. – 07EBKEE042
ABOUT COMPANY
NTPC Limited (Formerly National Thermal Power
Corporation) is the largest power generation company in India and was
founded on November 7, 1975. Forbes Global 2000 for 2009 ranked it 317th in
the world.
National Thermal Power Corporation has been the power behind India’s
sustainable power development since November 1975. Contributing 26% of
country’s entire power generation, it has placed itself in the Nav - Ratan
companies of Indian government and hence is the public sector company.
The total installed capacity of the company is 31134 MW (including JVs) with
15 coal based and 7 gas based stations, located across the country. In addition
under JVs, 3 stations are coal based & another station uses naphtha/LNG as
fuel.
NTPC has been operating its plants at high efficiency levels. Although the
company has 18.79% of the total national capacity it contributes 28.60% of total
power generation due to its focus on high efficiency. NTPC’s share at 31 Mar
2001 of the total installed capacity of the country was 24.51% and it generated
29.68% of the power of the country in 2008-09.
The company has set a future goal of having 50000 MW of installed capacity
by 2012 and 75000 MW by 2017. The company has taken many steps like stepup its recruitment, reviewing feasibilities of various sites for project
implementations etc. and has been quite successful till date.
CONTACTS
Barh Super Thermal power Project
Location P.O – Barh
District – Patna
Bihar – 803213
Phone – 06132 – 240011 / 12 / 13
Fax – 06132 – 240010 , 240014
Regd.Off : NTPC Bhawan , Scope Complex, 7,Institutional Area,
Lodhi Road,New Delhi - 3
PROJECT UNDERTAKEN
 To study switchtard and its various equipment including testing of the
equipments.
CHALLENGES FACED
 It was really hard to analyse the complex system of switchyard at that
high level of system voltage .
 It was first time to work at a plant premises in disciplines and rules.
THEORY
BARH SUPER THERMAL
POWER PROJECT
A Study Project Report On
400 KV And 132 KV
SWITCH YARD
Submitted By :-
Submitted To :-
Praveen Kumar
B.Tech (3rd YR)
Electrical Engineering
B.K.B.I.E.T , Pilani
Rajasthan – 333031
Mr. Amit Tripathi
Sr. Engineer
EE Department
NTPC , Barh
Bihar - 803213
Barh Super Thermal Power Project , P.O-Barh, Dist.-Patna,
Bihar-803213
ACKNOWLEDGEMENT
I sincerely acknowledge the co-operation and complete support rendered by
Mr.Amit Tripathi, Sr. Engineer(EE) of Barh Super Thermal Power Project
(Barh STPP) who introduced me to detailed working of plant and switchyard
and gave best possible information regarding the same .
I would take my opportunity to express my sincere gratitude to Mr.Vajira
Vel & Mr. Krishna Murthy (commissioning Er) for their active co-operation and
kind consideration in every stage of training .
Finally I express my sincere thanks to all team members of EED who
directly or indirectly helped me to complete the training successfully.
PRAVEEN KUMAR
DATE :PLACE :-
CONTENTS
 BSTPP AT A GLANCE
 SWITCHYARD
CURRENT TRANSFORMER
CAPACITIVE VOLTAGE TRANSFORMER
CIRCUIT BREAKER
SURGE ARRESTOR
ISOLATOR
BUSBAR
LINETRAP
INSULATORS
EARTHING
SHUNT REACTOR
CONTROL AND RELAY PANEL
 TRANSFORMERS
GENERATING TRANSFORMER
UNIT TRANSFORMER
STATION TRANSFORMER
INTER CONNECTING TRANSFORMER
MISCELLANEOUS SERVICE TRANSFORMER
BSTPP AT A GLANCE
Project name
: BARH STPP
No. of units × capacity
: 3× 660MW(STAGE -I)
2× 660MW(STAGE -II)
Projects setting up by
: National thermal power corporation Ltd. (NTPC
Ltd.)
Location:
The project site is located about 3kms east of Barh town in Patna district
in the state of Bihar, having a latitude and longitude of 25 deg 28' N and 85deg
45' E respectively. The plant and township are located between NH-31 and
railway line. The ash disposal area is located in the south of the railway line.
Land requirement:
Approximately 1200 acres of land has been identified between NH1 and railway lines for the plant area, switchyard, green belt, labour colony, ash
based units and township. approximately 1750 acres of land has been identified
for the ash disposal area in the south of railway line.
Coal availability and linkage:Coal requirement for Barh STPP, stage-1 is proposed to be met
from Amarpali block of north Karanpura coalfields. Coal requirement for the
project in estimated as 10 million tones/annum considering a GCV of 3350
kcal/kg and 80% PLF.
Coal transportation:Coal from amarpali block of north karanpura coalfields is proposed
to be transported to the project site through Indian railways system for a
distance of approximately 250kms via shorter route .
Water requirement: The project site is located near the river Ganges. The make up water
requirement for the project is proposed to be drawn from river Ganges near
village Nawada, at a distance of 2kms. The make up water requirement for the
project is estimated as 9200 m3/hr with ash water recirculation system and
10200 m3/hr once through ash water system respectively. A closed cycle
cooling water system using induced draft cooling towers is proposed.
Construction power:
The requirements of the construction power supply for the project
would be met at 33Kv level from the nearby BSEB substations. Necessary
33kV substation and 11kV ring main /LT substations shall be provided for the
power plant area.
Power Evacuation system: Power generated is proposed to be stepped up to 400kV by
generator transformer and will be evacuated through the transmission system
to be evolved and implemented by Power Grid Corporation of India Ltd. The
switchyard at power plant end is owned by NTPC.
Beneficiary states:The states & UTs of Northern & Western regions and state of Bihar.
SWITCHYARD
Switchyard is considered as the HEART of the Power Plant. Power generated
can be worthy only if it is successfully transmitted and received by its
consumers. Switchyard plays a very important role as a junction between the
generation and transmission. It is a junction, which carries the generated power
to its destination (i.e. consumers).
Switchyard is basically a yard or an open area where many different kinds of
equipments are located (isolator, circuit breaker etc…), responsible for
connecting & disconnecting the transmission line as per requirement (e.g. any
fault condition).
Power transmission is done at a higher voltage. (Higher transmission voltage
reduces transmission losses resulting in higher utilisation of generating capacity
and optimises the resource required for capacity addition.).
Therefore, the power generated by the Turbogenerator of 1 to 5 units is 24KV
which is stepped-up to 400KV by the Generating transformer & then
transmitted to switchyard.
In BSTPP there are two switchyards:(i) 400KV SWITCHYARD
(ii) 132KV SWITCHYARD
Switchyard is classified in three categories :  Conventional Air Insulated Type.
 Gas Insulated type.
 Outdoor Gas Insulated type.
At BSTPP 400 KV and 132 KV Switchyards are of type Conventional Air
Insulated Type.
.
400 KV SWITCHYARD
There are total 22 bay in 400 KV switchyard. A Bay is basically a way for the
incoming power from generator as well as outgoing power for distribution.







5 Bay for each generating transformer
3 Bay for ICT(Inter Connecting Transformer)
2 Bay for PATNA line
2 Bay for KAHALGAON line
2 Bay for BALIA line
7 for FUTURE line
1 Bay for SHUNT REACTOR
There are four main buses in 400 KV switchyard.
 Main bus – 1& 2
 Main bus – 3&4
132 KV SWITCHYARD
There are total 11 Bay in 132 KV switchyard.




3 Bay for ICT (Inter Connecting Transformer)
5 Bay for S.T (Station Transformer)
2 Bay for MST (Miscellaneous Service Transformer)
1 Bay for Bus Coupler
There are two main buses in 132 KV switchyard.
 Main bus - 1
 Main bus - 2
CURRENT TRANSFORMER
The current transformer is a step up transformer , it means current is stepped
down to a very low value (generally 1 A or 5 A) so that it can be used for
measuring and protection purposes .
C.T is designed in such a way its Core Material could give high accuracy with
low saturation factor. Core Material is generally made of CRGO Silicon steel
For very low loss characteristics, µ material (Alloy of Ni-Fe) is used.
Current Transformer is used for basically two major functions:  Metering which means current measurement.
 Protection such as over current protection, overload earth fault
protection, Bus-bar protection, Bus differential protection.
CT is typically described by its current ratio from primary to secondary. There
is not more difference between 132 KV and 400 KV C.T , only current ratio
differs
TESTING OF A C.T
 Insulation resistance
 Winding resistance
 Polarity
 Knee point test or magnetising current
 Turns Ratio test
 Primary Current Injection Test
 Tan Delta test
SPECIFICATIONS OF 132 KV C.T
o
o
o
o
o
o
o
Standard
Highest System Voltage
Insulation Level
Frequency
Short Time Current
Rated Primary Current
Extended Current
TERMINAL RATIO
VA
1s1-1s2
1s1-1s3
1s1-1s4
2s1-2s2
2s1-2s3
2s1-2s4
3s1-3s2
3s1-3s3
3s1-3s4
4s1-4s2
4s1-4s3
4s1-4s4
5s1-5s2
5s1-5s3
5s1-5s4
20
20
20
-
300/1 A
600/1 A
1200/1 A
300/1 A
600/1 A
1200/1 A
300/1 A
600/1 A
1200/1 A
300/1 A
600/1 A
1200/1 A
300/1 A
600/1 A
1200/1 A
IS2705
145 KV
275/650 KV
50 Hz
31.5 KA for 1 sec
1200 A
120%
CLAS
S
PS
PS
PS
PS
PS
PS
0.5
0.5
0.5
5P20
5P20
5P20
PS
PS
PS
Kp
300v/160mA
600v/80mA
1200v/40mA
300v/160mA
600v/80mA
1200v/40mA
300v/160mA
600v/80mA
1200v/40mA
300v/160mA
600v/80mA
1200v/40mA
OHMS
at 75 C
2.5Ω
5Ω
10 Ω
2.5Ω
5Ω
10 Ω
2.5Ω
5Ω
10 Ω
2.5Ω
5Ω
10 Ω
PURPOSE
Protection
protection
Protection
Protection
Protection
Protection
Metering
Metering
Metering
Protection
Protection
Protection
Protection
Protection
Protection
SPECIFICATIONS OF 400 KV C.T
o
o
o
o
o
o
o
o
o
o
o
o
o
Standard
IS2705
Rated Voltage
420 KV
Insulation Level
275/650 KV
Frequency
50 Hz
Short Time Current
31.5 KA for 1 sec
Rated Continous normal Current
2000 A
Extended Current
200/120%
Oil weight
750 Kg
Total weight
2500 Kg
Short time thermal current withstand for
40 kA for 1 sec
Dynamic current withstand
100 (kA peak)
No. of cores per CT
5
Transformation ratio
3000-2000-1000/1-1 (Cores 1 & 2 )
3000-2000-1000-500/1-1-1 (Cores 3, 4& 5)
o BIL
630/1425 KV
Ratio
Core number
Rated primary current(A)
Rated sec. Current(A)
Output(VA)
Accuracy class
I.S.F/A.L.F
Rct at 75 c (ohms)
KPV (V)
Lexc at Vk (mA)
3000-2000-1000/1-1
3000-2000-1000-500/1-1-1
1
2
3
4
5
3000
1
1
1
1
1
20
PS
PS
0.2
PS
PS
≤5
15
10
5 15 10 5 2.5
3000 2000 1000 6000 4000 2000 1000
20
30
60 20 30 60 120
CAPACITIVE VOLTAGE TRANSFORMER
It is a step down transformer, which step down the high voltage to a lower value
that can be measured using the measuring instruments . The CVT are connected
between phase and ground in parallel to the circuit. The other most important
function of C.V.T is that it blocks power frequency of 50Hz and allows the flow
of carrier frequency for communication.
CVT Construction Details
There are 280 – 300 elements in C1 & C2 as these are stacks of capacitors.
C1 contains about 260 to 280 elements. C2 will be containing 15 to 20
elements. Ratio of C1/ C2 is about 20
400/ 20 = 20kV (Tap Voltage)
CVT Secondary Voltage v = k * V * C1/ (C1+C2)
V – Primary Voltage , k – Secondary Transformation ratio
SPECIFICATIONS OF 400 KV CVT
o
o
o
o
o
o
o
o
o
o
o
Standard
Primary voltage
Phase
Insulation level
Highest system voltage
Temp cat.
Type
Weight
CN
C1
C2
Secondary
terminal
Secondary volts
Rated burden(VA)
Class
Frequency(Hz)
1a-1n
1a’-1n
110/sqrt(3)
200
3P
48-51
TESTING OF A CVT





Megger(IR)
Winding resistance
Ratio test
Tan-delta test
Capacitance
IS:3156
400kv/sqrt(3)
single
630/1425 KVP
420 KV
50˚c
outdoor
1130 Kg
4400 pF
4656 pF
80000 pF
2a-2n
2a’-2n
110/sqrt(3)
200
3P
48-51
3a-3n
110/sqrt(3)
100
0.2
49.5-50.5
CIRCUIT BREAKER
A circuit breaker is an automatically-operated electrical switch designed to
protect an electrical circuit from damage caused by any disturbance in power
system. Its function is to interrupt continuity, to immediately discontinue
electrical flow. It can be used in off-load as well as on-load condition.
When a circuit breaker is operated by sending an impulse through relay, C.B.
contact is made or broken accordingly. During this making and breaking, an arc
is produced which has to be quenched; this is done by air, oil, SF6 gas etc….
Depending on the arc quenching medium being used C.B.s can be categorized
into various types. In BSTPP for 400 KV/132 KV switchyard only one type is
being used: ACB (Air break circuit breaker):- operated as well as
arc quenched through air.
 BOCB (Bulk oil circuit breaker):-arc quenching done through oil
(Aerosol fluid oil).
 MOCB (Minimum oil circuit breaker):-arc quenching done through oil
(Aerosol fluid oil).
 ABCB (Air Blast Circuit Breaker):- arc quenching done by blast of air
 SF6 circuit breaker:- arc quenching done through SF6 gas.
Hydraulic operated SF6 circuit breaker is the most efficient due to following
reasons:1. Less maintenance.
2. Arc quenching capability of SF6 gas is more effective than
air.
3. Heat transfer capacity is better in this C.B.
TESTING OF A CIRCUIT BREAKER





Insulation resistance
CRM(contact resistance measurement)
DCRM(Dynamic contact resistance measurement)
Closing time test
Opening time test







Closing coil & trip coil resistance
Pickup drop of coils
Antipumping Relay operation
Pole discrepancy
SF6 lock out
N2 lockout
Hydraulic Oil lockout
SPECIFICATIONS OF A 132 KV CB
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
C.B type
Voltage
Lightning imp. With voltage
Power freq. With voltage
Frequency
Normal current
Gas pressure SF6
Maximum working pressure
Operating device type
Breaking current
Making current
Short time current
Total mass
Mass of gas
Temperature class
First pole to clear factor
Operating sequence
LTB145D1/B
145 KV
650 KV
275 KV
50 Hz
1250 A
abs(+20˚c)
9.0 bar
BLK222
31.5 KA
80 KA
31.5 KA
1710 Kg
6.8 Kg
-5˚c
1.3
O-0-3s-CO-3min-CO
SPECIFICATIONS OF A 400 KV CB
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
C.B type
3AT2
Rated Voltage
420 KV
Number of poles
3
Whether 3 pole or single pole unit
Single pole unit linked together
Whether dead tank or live tank design
live tank design
No. of breaks per pole
two
Rated imp.Withstand voltage
1050/1425 KVp
Rated Power freq. Withstand voltage
520/610 KV
Frequency
50 Hz
Rated Normal current
3150 A
Rated pressure of SF6
8.5 bar (+20˚c)
Breaking current (symmetrical)
40 KA
Making current
100 KAp
Short time current
40 KA
Short time duration
1 sec
Total weight
9290 Kg
Weight of SF6 gas
67.5 Kg
Temperature class
-5˚c
First pole to clear factor
1.3
Rated Operating duty
O-0.3secs-CO-3mins-CO
Rated trip coil voltage
220±10 VDC
Rated closing coil voltage
220±10 VDC
Rated pressure of hydraulic oper. Mech.
313±3 bar
Rated break time
40 ms
Closing time
120 ms
Type of installation
Outdoor
Type of closing & opening mechanism
Electro Hydraulic
Minimum dead time for three phase reclosing
300 ms
Minimum dead time single phase reclosing
300 ms
SURGE ARRESTOR
It is a protective device, which protects the costly equipments such as overhead
lines, poles or towers, transformer etc. against lightening impulses and
switching impulse. As the name suggests it arrests the lightening of very high
voltage (thousands of KV) and dump it into the ground.
It works on the principle of easy path for the flow of current. S.A. is connected
in parallel with the line with its lower end connected and the upper end
projected above the pole of tower.
Lightning arrestor on its continuous operation drives a small amount of driving
current usually of magnitude 0.1 to 0.8 mA . for monitoring this leakage current
we use a surge monitor as this leakage current increases with time which
indicates the aging of arrestor.
CHARACTERISTICS OF SURGE ARRESTOR
SPECIFICATIONS
o
o
o
o
o
o
o
o
o
o
Standard
Arrestor class
Type
Rated arrestor voltage
Nominal discharge current
Continuous operating voltage at
designed temperature
Line discharge class as per IEC
One minute power freq. Withstand voltage
Impulse current withstand(high current
4/10µsec wave long duration)
Lightning impulse withstand voltage
1.2/50 µsec wave
TESTING




Insulation resistance
Counter
Leakage current monitor test
Capacitance test
IEC-60099-4
station class
gapless type
390 KV(rms)
10 kA
303 kV
class – III
630kV(rms)
100kAp
±1425 kVp
ISOLATOR
An isolator is one, which can break an electrical circuit when the circuit is to be
switched on no load. These are normally used in various circuits for the
purposes of isolating a certain portion when required for maintenance etc. It is
always used in OFF-LOAD condition.
"Switching isolators" are capable of
 Interrupting transformer magnetized currents;
 Interrupting line charging current; and
 Load transfer switching.
Generally we have a provision for a earth switch associated with a
isolator .“Earth switches” are devices which are normally used to earth a
particular system to avoid accident, which may happen due to induction
on account of live adjoin circuit. These do not handle any appreciate
current at all.
TESTING







Insulation resistance
CRM(contact resistance measurement)
Open time
Close time
Closing coil resistance
Opening coil resistance
Pickup drop of coils
BUS BAR
Bus bar are used to interconnect the loads and sources of electrical power . It
connects incoming and outgoing transmission lines.It also connect generator
and main transformer in power plant. Copper or Aluminium are generally used
for busbar
The bus bars of 400 kV switchyard are generally made up 4 “IPS aluminum
tube or Quad Moose rated for 3000 A”.
The bus bars of 220/132kV switchyard are generally made up of 3 “IPS
aluminum tube or quad/ twin moose conductor”. Bus bars are placed at right
angles to the feeders for tapping the power.
There are different bus schemes for a switchyard, depending on certain factors
such as feeder fault, bus fault and redundancy in design.








Single sectionalised bus
Main and transfer bus
Sectionalised Main bus with transfer bus
Sectionalised double main and transfer bus
Double Bus Scheme
Ring bus
One and a half breaker
Double bus, double breaker
One and a half breaker bus scheme is adopted for 400 KV switchyard at
BSTPP.
While for 132 KV switchyard one Main and transfer bus scheme is adopted.
LINETRAP
It is an equipment used to trap the high carrier frequency of 20Hz to 20 KHz
and above and allow the flow of power frequency (50 Hz). High frequencies
also get generated due to capacitance to earth in long transmission lines. The
basic principle of wave trap is that it has low inductance (2 Henry) & negligible
resistance, thus it offers high impedance to carrier frequency whereas very low
impedance to powerfrequency hence allowing it to flow in the station.
Generally there are two class of linetrap depending upon the value of
inductance. Inductance value may be of 1.0 mH or 0.5 mH.
PLCC(Power Line Carrier Communication)
As the name suggests, P.L.C.C. is basically a method in which the line used for
power transmission is also being used for communication.
P.L.C.C is employed for performing following two functions:
(i) Communication purposes.
(ii) Protection
Communication Purpose:
There are two types of electrical frequency which flow in a line- 50Hz power
signal & 20 KHz of carrier signal. In order to isolate these two frequencies (so
that they do not hinder each other) tapping of the frequencies is done as per the
requirement.
Since in the buses and bays we need only power frequency, wavetraps are being
used to block high frequency carrier signals. C.V.T. blocks the power
frequencies and due to the capacitance present it allows the high frequency
carrier signals to pass through co-axial cables.
Protection
Transmission line between two sub-stations is bi-directional. When a fault
occurs and a trip command is given at one end, the breaker gets opened. Now
the other end breaker should also be opened to completely isolate the line from
supply. For this the other end should also give the trip command. This is when
the P.L.C.C. comes into play. From the P.L.C.C. room present at the tripping
end along with the carrier signal, a signal of a lesser frequency is superimposed
and sent to the P.L.C.C. room present at the other end. Now this will be
demodulated and the other end will come to know that tripping has occurred.
Now it will give a command, which will energize the relay, contact will be
made and the breaker will operate.
INSULATORS
Generally we use two types of insulator in a switchyard
o Suspension type insulators
o Post type insulators
Suspension insulators or string insulators are used to align aluminium
conductors . each individual disc has a rated voltage of about 16kV. Post type
insulators provide horizontal support to the aluminium tube busbar.
SPECIFICATIONS OF POST INSULATORS
o
o
o
o
o
o
o
o
o
o
Standard
Type
No. of units per stack
Nominal system voltage
Highest system voltage
Lightning imp. withstand voltage
Switching surge withstand voltage
Ultimate cantilever strength(Min)
Ultimate tensile strength
Net weight
IS:2544-1973/IEC 168-1994
solid core post type
three
400 kV(rms)
420 kV(rms)
1550 kVp
>1175kVp
8 KN
160 KN
300 Kg
EARTHING
Earthing is to be provided in substations due to following reasons: The object of earthing is to maintain a low potential on any object.
 The purpose of a earthing system in a substation area is to limit the
potential gradient within and immediately outside the area to a value ,
safe for the working personnel. Safety is to be ensured under normal as
well as under abnormal conditions
 To provide a means to carry electric current into the earth under normal
and fault conditions , without exceeding any operating and equipment
limits or adversely affecting continuity of service .
At BSTPP solid earthing is done in 132 KV and 400 KV switchyard.
Following basic require are to be satisfied so as to ensure a
proper earthing system
o The earth resistance for the switchyard area should be lower than a
certain limiting value in order to ensure that a safe potential gradient is
maintained in the switchyard area and protective relay equipment operate
satisfactorily. For major switchyards and substations in India this limiting
value of earth resistance is to be taken less than 0.5 ohm.
o The grounding conductor material should be capable of carrying the
maximum earth fault current without over-heating and mechanical
damage. The maximum fault level in the 400KV has been estimated to
be 40kA and this value of fault current is is to be used in design of earth
mat for the 400 kV substation.
o All metallic objects which do not carry current and installed in the
substation such as structures, parts of electrical equipments, fences,
armouring and sheaths of low voltage power and control cables should be
connected to the earthing electrode system.
o The design of ground conductor should take care of the effect of
corrosion for the total life span of the plant .
SHUNT REACTOR
Shunt reactors installed at a switchyard serve two purposes : Whenever there is a increase in system voltage due to capacitance
formation it injects inductive power to the system and thus neutralizes it.
 Shunt reactor also limits the faults current .
SPECIFICATIONS
o
o
o
o
o
o
o
o
o
o
o
o
Type
Cooling
Rated power
Rated current
Phase
Connection symbol
Frequency
Lightning impulse
Switching impulse
Power frequency
Oil quantity
Total weight
core type
ONAN
80 MVAr
109.97 A
3
Yn
50 Hz
1300kVp(line),550kVp(neutral)
1050 kVp
364kVp(line),230kVp(neutral)
40780 litre
128755 Kg
CONTROL AND RELAY PANEL
Control panel mostly consists of meters and protective relays. The meters
include ammeter, voltmeter, wattmeter, energy meter etc. The relays include
over voltage relay, over current relay , over frequency relay , under voltage
relay , under frequency relay , earth fault relay , master trip , distance relays.
auxiliary relay and transformer relays like OLTC out of step, winding
temperature alarm, oil temperature alarm. The trip indicators included are CB
SF6 gas density low, CB Air pressure low, VT fuse fail alarm, CB pole disc
trip, carrier signal received, back up protection, auto reclose lock out, control
DC supply fails, distance protection , carrier out of service, distance
protection trip etc.
TRANSFORMER
A transformer is a device that transfers electrical energy from one circuit
to another through inductively coupled conductors — the transformer's coils. A
varying current in the first or primary winding creates a varying magnetic field
through the secondary winding. This varying magnetic field induces a varying
electromotive force (EMF) or "voltage" in the "secondary" winding. This effect
is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the
secondary winding and electrical energy will be transferred from the primary
circuit through the transformer to the load. In an ideal transformer, the induced
voltage in the secondary winding (VS) is in proportion to the primary voltage
(VP), and is given by the ratio of the number of turns in the secondary (NS) to
the number of turns in the primary (NP) as follows:
GENERATING TRANSFORMER
A generating transformer is a single – phase power transformer(3 single phase
units shall form a bank) . Generating Transformer steps–up the generated
voltage of 24 KV by alternator to a higher voltage of 400 KV (hence, working
as a step-up Transformer).This voltage of 400 KV is then transmitted to
switchyard.
SPECIFICATIONS
o
o
o
o
o
o
o
o
o
o
Type Of Cooling
Vector Group
HV Nominal Voltage
LV Nominal Voltage
Rated Power
HV Nominal Current
LV Nominal Current
Frequency
Phases
Lightning impulse withstand voltage
o System fault level
o Winding connection
o Tap range
o Oil weight
o Total weight
OFAF
YNd11 after 3 phase
420/sqrt(3) KV
24 KV
260 MVA
1072.22 A
10833.33 A
50 Hz
single phase *
1425 kVp(HV)
170 kVp(LV)
95 kVp(HVn)
40 kA
star (HV)
delta (LV)
solidly grounded(HVn)
± 5% in steps of 2.5%
on HV neutral side
60430 Kg
250930Kg
INTER CONNECTING TRANSFORMER
An ICT is a 3-phase auto transformer used to interconnect 400 KV
switchyard and 132 KV switchyard.
SPECIFICATIONS
o
o
o
o
o
Standard
Type of cooling
Type
Vector group
Rated power
o Current rating of different cooling
o
o
o
o
Power rating of different cooling
Phase
Frequency
Winding connection
o
o
o
o
Core and winding mass
Oil mass
Total oil quantity
Switching impulse
IS:2026
ONAN/ONAF/OFAF
Auto Transformer
YNa0d11
200 MVA(HV)
200 MVA(MV)
67 MVA(LV)Reactive
5 MVA Active
40% /60%/100% (A)
40% /60%/100% (MVA)
Three
50 Hz
star(HV)
star(MV)
delta(LV)
solidlygrounded(HVn)
115600 Kgs
81880 Kgs
92000 litre
1180 KV(HV)
STATION TRANSFORMER
Station Transformer is used only for initializing the start-up of the station (Main
Plant).It is very beneficial during emergency situations such as tripping of
Units, shut-down etc. Station transformers is used to start Station auxiliaries a
which are required for generating services such as coal and ash handling
system, lighting system, water purifying system etc.
It gets the supply in its primary from 132 KV switchyard, stepsdown it to 11.5
KV which is used for starting various equipments & devices used in the Main
Power Plant.
SPCIFICATIONS
o
o
o
o
o
Standard
Type
Rated output
Cooling
Rated voltage
o Rated load current
o GTD. Temp rise
@ 50˚c Ambient
o Basic insulation level(IMP/P.F)
o
o
o
o
Vector group
Core & coil mass
Oil quantity
Total mass
IS:2026/77-81
Three Winding
90/45/45 MVA
ONAN/ONAF
132 KV (HV)
11.5 KV(LV1 & LV2)
236.19 / 393.65(HV)
1353.52/2259.20(LV1)
1353.52/2259.20(LV2)
50˚c (OIL)
55˚c (WDG)
650/275 (HV)
75/28 (LV1&LV2)
170 /70 (HVn)
YNyn0yn0
60500 Kg
33700 Litre
121500 Kg
UNIT TRANSFORMER
Unit transformer is directly coupled to the unit itself so when that unit is in
running condition it supplies power to which are coupled to auxiliaries directly
or through unit auxiliary transformer depending upon load. Unit auxiliaries are
those which are directly associated with the generating unit such as ID and FD
fans, Boiler feed pumps, coal mills, fans, circulating water pumps etc.
SPECIFICATIONS
o
o
o
o
o
o
o
o
o
o
Rated output
Cooling
Type
Voltage ratio
Frequency
Phases
ONAN rating
ONAF rating
Vector group
Lightning impulse
withstand voltage
o One minute power frequency
withstand voltage
35 MVA
ONAN/ONAF
two(2) winding
24 / 11.5 KV
50 Hz
Three
min 80% of rated MVA
rated MVA
Dyn1
170 KVp (HV)
75 KVp (LV)
75 KVp (LVN)
70 KV (HV)
28 KV (LV)
27 KV (LVN)
MISCELLANEOUS SERVICE TRANSFORMER
Miscellaneous service transformer are used to supply miscellaneous loads of
plant. It is a two winding transformer connected to 132 KV switchyard.
SPECIFICATIONS
o Standard
o Rated output
o Full load rated current
o
o
o
o
o
o
o
o
o
o
o
o
Cooling
Type
Voltage ratio
Frequency
Phase
Vector group
Lightning impulse
withstand voltage
One minute power frequency
withstand voltage
GTD. Temp rise at
@50˚c ambient
Core & coil mass
Oil quantity
Total mass
IS:2026/77-81
16 MVA
69.98 A
803.27 A
ONAN
Two winding
132 / 11.5 KV
50 Hz
Three
YNyn0
650 KVp (HV)
75 KVp (LV)
275 KV (HV)
25 KV (LV)
50˚c (OIL)
55˚c (Wdg)
17650 Kg
10400 litre
37600 kg
APPLICATION DEVELOPED:

Successful study of a EHV switchyard and its equipments including
testings .
SCREEN SHOTS
SECTIONAL VIEW OF A 400 KV SWITCHYARD
MULTI CIRCUIT TRANSMISSION TOWER
ALUMINIUM TUBE BUSBAR
ALUMINIUM CONDUCTOR
400 KV SF6 CIRCUIT BRAKER
GENERATING TRANSFORMER