SYNCHRONOUSGENERATORTURBINE

GOVERNOR

EXCITATIONTRANSFORMER

2

EXCITATIONSYSTEM

GENERATORBREAKER1

1

SYNCHRONIZING

2

PROTECTION

STATIC STARTER

CONTROL SYSTEMS

AC & DCAUXILIARY SYSTEMS

STEP UP TRANSFORMER

HV- BREAKER

HV SYSTEM CONTROL ROOM

PT’s&CT’s

AUX.TRANSF.

STARPOINT

CUBICLE

LV SWITCHGEAR

The power station

• Generators• Excitation System• Transformers• MV Switchgear• EHV Switchgear• Generator

protections

Overview of Electrical Systems

•EHV protections

•Black Start DG set

•DC Systems

•415 V Systems

•Fire protection systems

•Switchyard Equipments

General Classification

ELECTRICAL SYSTEMS

AC 50 Hz SUPPLY SYSTEM D/C SYSTEM

220 KV 3 PHASE FOR BULK POWER TRANSMISSION

10.5 KV,15.75 KV 3 PHASE GENERATOR OUTPUT VOLTAGE

6.6 KV 3 PHASE FOR STATION AUXILLIARIES

415 V 3 PHASE FOR LOW VOLTAGE AUXILLIARIES

240 V SINGLE PHASE SUPPLY

220 V FOR UPS & EMERGENCY SYSTEMS

24 V FOR SOLENOIDS,

CONTROLLERS

48 V DC IN SWITCHYARD

GENERAL SINGLE LINE DIAGRAM

Turbo generator Excitation system Generator details

GAS TURBINE GENERATOR : 170.12 MVA,10.5kV,field voltage 410 V,stator current-9354 A- 2 NoSTEAM TURBINE GENERATOR : 188.23 MVA, 15.75kV,field voltage 432 V,stator current-6900 A- 1 NoAir cooled, 3000 RPM, 2 pole, double star.Four coolers in the generator for cooling the air.

–Providing variable DC current with short time overload capability

–Controlling terminal voltage,MVAR and PF with suitable accuracy

–Ensure stable operation with network and / or other machines

–Keep machine within permissible operating range

–Contribution to transient stability subsequent to a fault.

–Communicate with the power plant control system

• Apparent power• Active Power• Current• Voltage• Speed• Frequency• Power Factor• Stator Winding• Rated Field current• Rated Field Voltage

• 170.12MVA• 144.6MW• 9354A• 10.5KV+/-5%• 3000rpm• 50Hz• 0.85• YY• 833A• 410V

GT Generator

STG Generator

• Apparent power

• Active Power

• Current

• Voltage

• Speed

• Frequency

• Power Factor

• Stator Winding

• Rated Field current

• Rated Field Voltage

• 188.23MVA• 160MW• 6900A• 15.75KV+/-5%• 3000rpm• 50Hz• 0.85• YY• 798A• 432V

Steam Turbine Generator

The automatic voltage control system

SynchronousMachine

Excitation System

GridIf Ug

Controller

AVR

SM

High voltage line

Unit step up transformer

Excitation transformer

Sensing PT

Thyristor Converter

Synchronous machine

Static Excitation System

+ direct measuring of field -current, -voltage

+ superior dynamic performance (fast response)

+ field voltage reversing feature

+ very effective field discharge

+ Ceiling factor not limited

+ field ground dedection availabel

+ superior MTBF, MTTR

- Sliprings

Characteristic of Static Excitation System:

Brush less excitation system

• Just positive ceiling voltage capability

• Exciter response limited by the exciter machine time constant (>200ms)

• Field discharge with natural time constant

• Supply from PMG possible providing supporting of short circuit currents

• Relative large size of exciter machine for low speed generators

• No sliprings (less maintenance and dust)

Neutral terminal

• Grounding transformer used to reduce fault currents.

• The 100% stator earth fault detection is also done through this transformer

Starting system

• SFC manufacturer-AEG Germany

• Rating-2.9 MW

• Modes of operation:washing at 600 rpm

• Boiler purging at 900 rpm

• Unit black start at link circuit current 2.7 MW 1360 RPM

• Power operation at max dragging 2.9 Mw 2100 RPM

Transformers

• Generator transformer

• Unit auxiliary transformer

• Excitation Transformer

• MV/LV Transformers

• Lighting Transformers

• Three Phase, 153.5 MVA, BHEL make.

• Delta Star, neutral solidly grounded.

• 10.5/230 kV.• Cooling-ONAN/ONAF/

OFAF • Off circuit Tap changer at

five positions• Oil quantity:-39715 liters

Generator transformer UAT

• Rating 25 MVA 10.5/6.9 kV

• Cooling: ONAN/ONAF

• Quantity of oil-13095 liters

• On load tap changer at 12 positions

Busduct and UAT

Gen. Transformer

System

• There are two Unit Transformers connected thru GT, 10.5 KV Bus.

• These two Transformer make 2no. 6.6KV bus ( 11 &12 BBE) which in turn make another 2 bus thru Ties.(OCA- A&B)

• A total 4no 6.6KV bus exists which are interconnected thru Ties and Bus coupler.

• DG is also connected to OCA (A&B) bus thru 6.6KV Breakers.

6.6KV BUS SYSTEM

Changeover Schemes

Changeover Schemes are divided in Two Group: A. With Paralleling B. Without Paralleling Here there are Four Types of Schemes under these

Categories:• MANUAL Changeover • FAST Changeover• SLOW Changeover• BLACKOUT Condition

Manual Changeover Scheme

Features:

• It is a planned changeover.• Thru Operator Intervention.• No Interruption in Voltages.• Thru Synchronizing Relay

Manual Changeover Scheme

Scope:

1. Bus coupler at OCA

2. UAT Incomer ( BBE01&2)

3. DG Breaker 1&2

4.Tie Breaker at OCA( Tie1 &2)

Manual Changeover Scheme

Example :

U1-B/C-U2 Changeover:

--Proven scheme

--Either of Breaker can be closed thru ECB.

--Choice of Breaker tripping is done thru Trip selection switch.

Fast Changeover Scheme

Feature:• This is only for OCA Bus coupler.• This changeover occurs when Voltage sink is

likely to occur. • OCA Bus coupler will close in Auto without any

time delay. No manual Intervention possible.• This changeover will take place in less than

200millisecond, hence chances of supply interruption is very less.

Slow Changeover Scheme

Features:

• This is a backup of Fast changeover.

• Bus coupler will close in auto after certain Time delay and fulfillment of certain condition

• Chances of unit survival depends on situation

Black Out Condition

Normally blackout condition means:

• 1. All GCB and HVCB open.

• 2. Both Unit Incomer Breakers Open

• 3. No Auxiliary Power at station.

At this moment our attempt to restore the Auxiliary power as soon as possible.

Black Out Condition

Under this Condition:• DG set will take start in Auto• All Aux. Feeders at OCA Bus will Trip• Both DG Breakers will closed in Auto.• Priority Transformer feeders will close in Auto,

also their LT Incomers(except PCC) • Tie feeders at OCA and PCC will not Trip• This all will be done thru Logics As:

Black Out Condition Contd.

If due to any reason DG fail to start or DG Breaker does not close in Auto :

• Start DG Manually• Close the DG Breakers one by one• Close the Priority feeders one by one.

Black Out Condition --Normalisation

2. Thru GT1 and GT2 Transformer :• Back charge the transformer and close the U1 and

U2 breaker thru manual Changeover. D1 and D2 will trip respectively in auto.

3. Thru Unit Start Up.• Start Gas Turbine1/2 in Black Start mode. U1/U2

Breaker will close and D1/D2 will Trip in Auto.

Black Out Condition

Others:• During D1/D2 close condition—• Only Priority feeders can be closed- i.e ODA A

&B Breaker( Only emergency section, ODC I/c-A&B, and Common transformer breaker.)

• Other than Priority 6.6 KV fdr , no 6.6 KV fdr can be closed

• 415V,ODA-B/C D&E , CW &Chlorination fdr., OSF MCC, Nox and Misc MCC can not be closed.

Supply to Switchyard

Switchyard

EHV Control and Switchgear

• Circuit Breaker

• Isolator

• Current Transformer

• Capacitive Voltage Transformer

• Lightning Arrestor

• PLCC equipment

• Bus Switching Schemes

• Disturbance recorder

• Event logger

• Remote telemetering units

Line diagram

Bus Switching Schemes

3 Generators

Bus Coupler

Transfer Bay

4 Transmission lines

Transfer Bus

Main Bus-1

Main Bus-2

Double main and Transfer bus scheme

PLCC System

Tx

Rx

Tx

Rx

CVT

Wave trapSubstation A Substation B

Electrical Protections

• Generator and transformer protections• 6.6 kV Protections

– Station transformer protections – Motor protections– Transformer protections

• 220 kV Protections– Line protections– Bus bar protection– Breaker failure protection

VT Panel Protection Panel Terminal Box

Protection Panel

Numerical Relays

Backside of relays

Tripping Matrix

Tripping Relay

Generator Protection:Protection Functions (1)

Generator differentialOver current protectionVoltage dependent backupStator earth faultNeutral displacementSensitive directional E/F100% Stator E/FUnder & over voltageUnder & over frequency

87G50/5151V/2150/51N59N67N27TN27 & 5981U/O

2759

81O81U

51V21

50N51N

5051

67N

59N 27TN

87G

Reverse powerLow forward powerOverload powerField failureNegative phase seq.OverfluxingDead Machine (GUESS)RTD Thermal protection

32R32L32O40462427/5038/26Interconnectiondf/dt rate of change of frequencydVø Voltage vector shift

RTD

32R32L320

24

40 46

Generator Protection:Protection Functions (2)

MiCOM-P340-42

Settings

• Reverse Power Frequency • Under frequency • Overfrequency

• Rotor earth fault• Stator earth fault• Over Voltage• Under Voltage• Over Current• Under Excitation• Overflux • Generator Differential• Overall Differential• REF• Stator earth fault(95%)• Unbalanced Load

• -3.3 %

• 47.5 & 47.0 Hz• 51.5 & 52 Hz

• 5Kohm and 40 Kohm• 14ohm• 127V/ 143V• 70V• 125%• 5.04V• 1.1-1.4• 25%• 33%• 33%• 5V• 51% , 1.5Sec

STG GRP

6.6 kV Protections• Station transformer protections

– Three phase Over current protection.– Earth fault protection.– Restricted earth fault protection.

• Motor protection– IDMT over current protection– Earth fault protection

• Transformer protection– IDMT over current protection– Earth fault protection

EHV Protections

• Line protections

• Transformer protections

• Generator Protections

• Bus bar protection

• Breaker failure protection

Line protections

• Main I Distance protection (21-1)

• Main II Distance protection (21-2)

• Breaker failure relay.

• Trip circuit supervision relay

• Trip coil supervision relay.

• Fault locator

• Disturbance recorder

Distance Protection

Zone 1: 80%, 0mS

Zone 2: 120%,300mS

Zone 3: 200%,1000mS

A B

220 kV Transformer protections

• Transformer Differential protection.(87)• Three phase over current protection. (51)• Earth fault relay (Phase current balance)• Breaker failure relay.• Bucholz relay• Winding temperature relay• Oil temperature relay• Pressure relief device

DC SYSTEM

DC Systems

• 220 Volts DC Gas Turbine batteries

• 220 and 24 Volts Station batteries

• 432 Volts UPS batteries

• 220 Volts Emergency Lighting batteries

• 48 V Switchyard Battery systems

415 Volts System

• GT MCCs– All the LT auxiliaries of Gas turbine including:

• Auxiliary lube oil pump

• Generator cooling water pump motors

• GT cooling water pump motors

• Ventilation fans

• Battery chargers

• Jacking oil pump motor