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 step-up 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 Mr. Amit Tripathi

B.Tech (3rd YR) Sr. Engineer Electrical Engineering 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 TRANSFORMERCAPACITIVE VOLTAGE TRANSFORMERCIRCUIT BREAKERSURGE ARRESTORISOLATORBUSBARLINETRAPINSULATORSEARTHINGSHUNT REACTORCONTROL AND RELAY PANEL

TRANSFORMERSGENERATING TRANSFORMERUNIT TRANSFORMERSTATION TRANSFORMER

INTER CONNECTING TRANSFORMERMISCELLANEOUS 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 NH-1 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 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 CLASS

Kp OHMS at 75 C

PURPOSE

1s1-1s2 300/1 A - PS 300v/160mA 2.5Ω Protection1s1-1s3 600/1 A - PS 600v/80mA 5 Ω protection 1s1-1s4 1200/1 A - PS 1200v/40mA 10 Ω Protection2s1-2s2 300/1 A - PS 300v/160mA 2.5Ω Protection2s1-2s3 600/1 A - PS 600v/80mA 5 Ω Protection2s1-2s4 1200/1 A - PS 1200v/40mA 10 Ω Protection3s1-3s2 300/1 A 20 0.5 - Metering3s1-3s3 600/1 A 20 0.5 - Metering3s1-3s4 1200/1 A 20 0.5 - Metering4s1-4s2 300/1 A - 5P20 300v/160mA 2.5Ω Protection4s1-4s3 600/1 A - 5P20 600v/80mA 5 Ω Protection4s1-4s4 1200/1 A - 5P20 1200v/40mA 10 Ω Protection5s1-5s2 300/1 A - PS 300v/160mA 2.5Ω Protection

5s1-5s3 600/1 A - PS 600v/80mA 5 Ω Protection5s1-5s4 1200/1 A - PS 1200v/40mA 10 Ω 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)

o No. of cores per CT 5

o 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 3000-2000-1000/1-1 3000-2000-1000-500/1-1-1Core number 1 2 3 4 5Rated primary current(A) 3000

Rated sec. Current(A) 1 1 1 1 1Output(VA) - - 20 - -Accuracy class PS PS 0.2 PS PSI.S.F/A.L.F - - ≤ 5 - -Rct at 75 c (ohms) 15 10 5 - 15 10 5 2.5KPV (V) 3000 2000 1000 - 6000 4000 2000 1000Lexc at Vk (mA) 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 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

1a-1n1a’-1n

2a-2n2a’-2n

3a-3n

Secondary volts 110/sqrt(3) 110/sqrt(3) 110/sqrt(3)Rated burden(VA) 200 200 100Class 3P 3P 0.2Frequency(Hz) 48-51 48-51 49.5-50.5

TESTING OF A CVT

Megger(IR) Winding resistance Ratio test Tan-delta test Capacitance

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

o 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 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

o Number of poles 3

o Whether 3 pole or single pole unit Single pole unit linked together

o Whether dead tank or live tank design live tank design

o 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 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)

o Nominal discharge current 10 kA

o Continuous operating voltage at 303 kV

designed temperatureo 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 ±1425 kVp

1.2/50 µsec wave

TESTING

Insulation resistance Counter Leakage current monitor test Capacitance test

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

o Net weight 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 Type core type

o Cooling ONAN

o Rated power 80 MVAr

o Rated current 109.97 A

o Phase 3

o Connection symbol Yn

o Frequency 50 Hz

o Lightning impulse 1300kVp(line),550kVp(neutral)

o Switching impulse 1050 kVp

o Power frequency 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 Activeo Current rating of different cooling 40% /60%/100% (A)

o Power rating of different cooling 40% /60%/100% (MVA)

o Phase Three

o Frequency 50 Hz

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)

o 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

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)

o One minute power frequency 70 KV (HV)

withstand voltage 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 IS:2026/77-81

o Rated output 16 MVA

o Full load rated current 69.98 A

803.27 Ao Cooling ONAN

o Type Two winding

o Voltage ratio 132 / 11.5 KV

o Frequency 50 Hz

o Phase Three

o Vector group YNyn0

o Lightning impulse 650 KVp (HV)

withstand voltage 75 KVp (LV)o One minute power frequency 275 KV (HV)

withstand voltage 25 KV (LV)o 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

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 CONDUCTOR

ALUMINIUM TUBE BUSBAR 400 KV SF6 CIRCUIT BRAKER

GENERATING TRANSFORMER