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 NTPC Limi Limite ted d (Formerly Nati Nation onal al Th Ther erma mall Powe Powerr Corporation) is the the larg larges estt powe powerr gene genera rati tion on comp compan any y in Indi Indiaa and and was was founded on November 7, 1975. Forbes Global 2000 for 2009 ranked it 317th 317th in the world.
National Thermal Power Corporation has been the power behind India’s sustainable power development since November 1975. Contributing 26% of coun countr try’s y’s enti entire re powe powerr gene genera rati tion on,, it has has plac placed ed itse itself lf in the the Nav Nav - Rata Ratan n 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 installed capacity of the country was 24.51% and it generated 29.68% of the power of the country in 2008-09.
Student Name : Praveen Kumar Roll No. –
07EBKEE042
ABOUT COMPANY
NTPC NTPC Limi Limite ted d (Formerly Nati Nation onal al Th Ther erma mall Powe Powerr Corporation) is the the larg larges estt powe powerr gene genera rati tion on comp compan any y in Indi Indiaa and and was was founded on November 7, 1975. Forbes Global 2000 for 2009 ranked it 317th 317th in the world.
National Thermal Power Corporation has been the power behind India’s sustainable power development since November 1975. Contributing 26% of coun countr try’s y’s enti entire re powe powerr gene genera rati tion on,, it has has plac placed ed itse itself lf in the the Nav Nav - Rata Ratan n 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 installed capacity of the country was 24.51% and it generated 29.68% of the power of the country in 2008-09.
The company company has set a future goal of having having 50000 MW of installed installed capacity capacity by 2012 and 75000 MW by 2017. 2017 . The company has taken many steps like stepup its its recr recrui uitm tmen ent, t, revi review ewin ing g feas feasib ibil ilit itie iess of vari variou ouss site sitess for for proj projec ectt 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 time to work at a plant premises in disciplines disciplines and rules.
THEORY
BARH SUPER THERMAL POWER PROJECT
A Study Project Report On
400 KV And 132 KV SWITCH YARD
Submitted By :Praveen Kumar B.Tech (3rd YR) Electrical Engineering
Submitted To :Mr. Amit Tripathi Sr. Engineer EE Department
B.K.B.I.E.T , Pilani
NTPC , Barh
Rajasthan – 333031
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 m 3/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
Standard
IS2705
o
Highest System Voltage
145 KV
o
Insulation Level
275/650 KV
o
Frequency
50 Hz
o
Short Time Current
31.5 KA for 1 sec
o
Rated Primary Current
1200 A
o
Extended Current
120%
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
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
Standard
IS2705
o
Rated Voltage
420 KV
o
Insulation Level
275/650 KV
o
Frequency
50 Hz
o
Short Time Current
31.5 KA for 1 sec
o
Rated Continous normal Current
2000 A
o
Extended Current
200/120%
o
Oil weight
750 Kg
o
Total weight
2500 Kg
o
Short time thermal current withstand for
40 kA for 1 sec
o
Dynamic current withstand
100 (kA peak)
No. of cores per CT
5
o
o
Transformation ratio
3000-2000-1000/1-1 (Cores 1 & 2 ) 3000-2000-1000-500/1-1-1 (Cores 3, 4& 5)
o
Ratio
BIL
630/1425 KV
3000-2000-1000/1-1
3000-2000-1000-500/1-1-1
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)
1 1 PS 15 3000 20
2
3 3000 1 1 20 PS 0.2 ≤5 10 5 2000 1000 30 60 -
4
5
1 1 PS PS 15 10 5 2.5 6000 4000 2000 1000 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
Standard
IS:3156
o
Primary voltage
400kv/sqrt(3)
o
Phase
single
o
Insulation level
630/1425 KVP
o
Highest system voltage
420 KV
o
Temp cat.
50˚c
o
Type
outdoor
o
Weight
1130 Kg
o
CN
4400 pF
o
C1
4656 pF
o
C2
80000 pF
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
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
C.B type
LTB145D1/B
o
Voltage
145 KV
o
Lightning imp. With voltage
650 KV
o
Power freq. With voltage
275 KV
o
Frequency
50 Hz
Normal current
1250 A
o
Gas pressure SF6
abs(+20˚c)
o
Maximum working pressure
9.0 bar
o
Operating device type
BLK222
o
Breaking current
31.5 KA
o
Making current
80 KA
o
Short time current
31.5 KA
o
o
Total mass
1710 Kg
o
Mass of gas
6.8 Kg
o
Temperature class
-5˚c
o
First pole to clear factor
1.3
o
Operating sequence
O-0-3s-CO-3min-CO
SPECIFICATIONS OF A 400 KV CB o
C.B type
3AT2
o
Rated Voltage
420 KV
Number of poles
3
o
o
Whether 3 pole or single pole unit
o
Whether dead tank or live tank design
live tank design
No. of breaks per pole
two
o
Rated imp.Withstand voltage
1050/1425 KVp
o
Rated Power freq. Withstand voltage
520/610 KV
o
Frequency
50 Hz
o
Rated Normal current
3150 A
o
Rated pressure of SF6
8.5 bar (+20˚c)
o
Breaking current (symmetrical)
40 KA
o
Single pole unit linked together
o
Making current
100 KAp
o
Short time current
40 KA
o
Short time duration
1 sec
o
Total weight
9290 Kg
o
Weight of SF6 gas
67.5 Kg
o
Temperature class
-5˚c
o
First pole to clear factor
1.3
o
Rated Operating duty
O-0.3secs-CO-3mins-CO
o
Rated trip coil voltage
220±10 VDC
o
Rated closing coil voltage
220±10 VDC
o
Rated pressure of hydraulic oper. Mech.
313±3 bar
o
Rated break time
40 ms
o
Closing time
120 ms
o
Type of installation
Outdoor
o
Type of closing & opening mechanism
Electro Hydraulic
o
Minimum dead time for three phase reclosing
300 ms
o
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
Standard
IEC-60099-4
o
Arrestor class
station class
o
Type
gapless type
o
Rated arrestor voltage
390 KV(rms)
Nominal discharge current
10 kA
Continuous operating voltage at
303 kV
o
o
designed temperature o
Line discharge class as per IEC
class – III
o
One minute power freq. Withstand voltage 630kV(rms)
o
Impulse current withstand(high current
100kAp
4/10µsec wave long duration) o
Lightning impulse withstand voltage 1.2/50 µsec wave
TESTING
Insulation resistance
Counter
Leakage current monitor test
Capacitance test
±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
Standard
IS:2544-1973/IEC 168-1994
o
Type
solid core post type
o
No. of units per stack
three
o
Nominal system voltage
400 kV(rms)
o
Highest system voltage
420 kV(rms)
o
Lightning imp. withstand voltage
1550 kVp
o
Switching surge withstand voltage
>1175kVp
o
Ultimate cantilever strength(Min)
8 KN
o
Ultimate tensile strength
160 KN
Net weight
300 Kg
o
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
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. 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
Type
core type
o
Cooling
ONAN
o
Rated power
80 MVAr
o
Rated current
109.97 A
o
Phase
3
o
Connection symbol
o
Frequency
o
Lightning impulse
o
Switching impulse
o
Power frequency
Yn 50 Hz 1300kVp(line),550kVp(neutral) 1050 kVp 364kVp(line),230kVp(neutral)
o
Oil quantity
40780 litre
o
Total weight
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
Type Of Cooling
OFAF
o
Vector Group
YNd11 after 3 phase
o
HV Nominal Voltage
420/sqrt(3) KV
o
LV Nominal Voltage
24 KV
o
Rated Power
260 MVA
o
HV Nominal Current
1072.22 A
o
LV Nominal Current
10833.33 A
o
Frequency
50 Hz
o
Phases
single phase *
o
Lightning impulse withstand voltage
1425 kVp(HV) 170 kVp(LV) 95 kVp(HVn)
o
System fault level
40 kA
o
Winding connection
star (HV) delta (LV) solidly grounded(HVn)
o
Tap range
± 5% in steps of 2.5% on HV neutral side
o
Oil weight
60430 Kg
o
Total weight
250930Kg
INTER CONNECTING TRANSFORMER
An ICT is a 3-phase auto transformer used to interconnect 400 KV switchyard and 132 KV switchyard.
SPECIFICATIONS o
Standard
IS:2026
o
Type of cooling
ONAN/ONAF/OFAF
o
Type
Auto Transformer
o
Vector group
YNa0d11
o
Rated power
200 MVA(HV)
200 MVA(MV) 67 MVA(LV)Reactive 5 MVA Active o
Current rating of different cooling
40% /60%/100% (A)
o
Power rating of different cooling
o
Phase
Three
o
Frequency
50 Hz
40% /60%/100% (MVA)
o
Winding connection
star(HV) star(MV) delta(LV) solidlygrounded(HVn)
o
Core and winding mass
115600 Kgs
o
Oil mass
81880 Kgs
o
Total oil quantity
92000 litre
o
Switching impulse
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
Standard
IS:2026/77-81
o
Type
Three Winding
o
Rated output
90/45/45 MVA
o
Cooling
ONAN/ONAF
o
Rated voltage
132 KV (HV) 11.5 KV(LV1 & LV2)
o
Rated load current
236.19 / 393.65(HV) 1353.52/2259.20(LV1) 1353.52/2259.20(LV2)
GTD. Temp rise
50˚c (OIL)
@ 50˚c Ambient
55˚c (WDG)
o
Basic insulation level(IMP/P.F)
650/275 (HV) 75/28 (LV1&LV2) 170 /70 (HVn)
o
Vector group
YNyn0yn0
o
Core & coil mass
60500 Kg
o
Oil quantity
33700 Litre
o
Total mass
121500 Kg
o
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
Rated output
35 MVA
o
Cooling
ONAN/ONAF
o
Type
two(2) winding
o
Voltage ratio
24 / 11.5 KV
o
Frequency
50 Hz
o
Phases
Three
o
ONAN rating
min 80% of rated MVA
o
ONAF rating
rated MVA
o
Vector group
Dyn1
o
Lightning impulse
170 KVp (HV)
withstand voltage
75 KVp (LV) 75 KVp (LVN)
One minute power frequency
70 KV (HV)
withstand voltage
28 KV (LV) 27 KV (LVN)
o
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
IS:2026/77-81
o
Rated output
16 MVA
o
Full load rated current
69.98 A 803.27 A
o
Cooling
ONAN
o
Type
Two winding
o
Voltage ratio
132 / 11.5 KV
o
Frequency
50 Hz
o
Phase
Three
o
Vector group
YNyn0
Lightning impulse withstand voltage
650 KVp (HV) 75 KVp (LV)
One minute power frequency
275 KV (HV)
withstand voltage
25 KV (LV)
GTD. Temp rise at
50˚c (OIL)
@50˚c ambient
55˚c (Wdg)
o
Core & coil mass
17650 Kg
o
Oil quantity
10400 litre
o
Total mass
37600 kg
o
o
o
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
ALUMINIUM
TOWER
CONDUCTOR
ALUMINIUM TUBE BUSBAR
400 KV SF6 CIRCUIT BRAKER
