generator protection

GENERATOR PROTECTION

TURBO GENERATOR DIESEL GENERATOR HYDRO GENERATOR WIND GENERATOR


TYPES OF GENERATORS

SUB SYSTEMS OF GENERATORS

• STATOR

• ROTOR

• TRANSFORMER


GENERATOR MAIN-SYSTEMS

SUB SYSTEMS OF GENERATORS• STATOR• ROTOR• PRIME MOVER• EXCITATION SYSTEM• VOLTAGE REGULATOR• GOVERNOR• COOLING SYSTEM


GENERATOR SUB-SYSTEMS

FAULTS IN GENERATOR

EXTERNAL FAULTSINTERNAL FAULTSROTOR EARTH FAULTFAULTS RELATED TO SUB SYSTEMS


OVER LOADING

UNBALANCE LOADING

SHORT CIRCUIT

EARTH FAULT


EXTERNAL FAULTS

• PHASE TO PHASE FAULTS IN WINDINGS

• PHASE TO EARTH FAULTS


INTERNAL FAULTS

FAULTS RELATED TO SUB-SYSTEMS

UNDER VOLTAGEOVER VOLTAGEUNDER FREQUENCYOVER FREQUENCYREVERSE POWERLOSS OF EXCITATIONLOW-FORWARD POWER


GENERATOR PROTECTIONTYPES OF FAULTS (STATOR SIDE)

VOLTAGE RESTRAINED OVER CURRENTTHERMAL OVER LOADCURRENT UNBALANCEOVER VOLTAGEUNDER VOLTAGEOVER FREQUENCYUNDER FREQUENCYLOSS OF FIELDREVERSE POWERUNDER POWER

OUT OF STEPINADVERTANT ENERGISATIONEARTH FAULT (100%)EARTH FAULT (95%)

GENERATOR DIFFERENTIAL

OVER EXCITATION (V/Hz)


TYPES OF FAULTS (ROTOR SIDE)

ROTOR EARTH FAULTEXCITATION UNDER VOLTAGEEXCITATION UNDER CURRENTDIODE FAILURE


SINGLE LINE DIAGRAMGENERATOR PROTECTION

G

49 46 40

81

32

87G

51V 37 64

5927

11 kV

6.6 MW

400/5

400/5

400/5

11000/110v


PROTECTION PHILOSOPHY

TYPE OF GENERATORGENERATOR SIZENATURE OF GROUNDINGECONOMYTYPE OF CONNECTIONTYPE OF LOADS



ANOTOMY OF FAULTS

1.01.0 OVER CURRENT PROTECTIONOVER CURRENT PROTECTION

STATOR FAULTS (EXTERNAL )

PLAIN OVER CURRENT ( SMALL MACHINES)

VOLTAGE DEPENDANT OVER CURRENT(LARGE MACHINES)

1.01.0 PLAIN OVER CURRENT PROTECTIONPLAIN OVER CURRENT PROTECTION


RELAY ON BREAKER SIDE

RELAY ON NEUTRAL SIDE

1.01.0 PLAIN OVER CURRENT PROTECTIONPLAIN OVER CURRENT PROTECTION


FAULT AWAY FROM TERMINALS(PLAIN O/C PROTECTION)

FAULT CLOSE TO TERMINALS (VOLTAGE DEPENDENT O/C)

VOLTAGE DEPENDENT OVER CURRENTVOLTAGE DEPENDENT OVER CURRENT

- WHEN O/C FAULT, TERMINAL VOLTAGE REDUCES.- RELAY MAY NOT TRIP, SINCE FAULT CURRENT THROUGH RELAY MAY BE LESS THAN SET POINT

NECESSARY TO VARY THE O/C PICK UP SETTINGWITH RESPECT TO VOLTAGE

STATOR FAULTS

VOLTAGE CONTROLLED OVER CURRENTVOLTAGE CONTROLLED OVER CURRENT

STATOR FAULTS

HAS TWO TRIP CHARACTERISTICS

THE TERMINAL VOLTAGE DECIDESWHICH CHARCTERISTIC WILL BE FOLLOWED BY THE RELAY WHENA FAULT OCCURS

VOLTAGE CONTROLLED OVER CURRENTVOLTAGE CONTROLLED OVER CURRENT

STATOR FAULTS

I >

kI >

Vs >Voltage Level

Pick up level

VOLTAGE RESTRAINED OVER CURRENTVOLTAGE RESTRAINED OVER CURRENT

V/Vs

I*/ [I>]

0.2 0.8

0.2

1.0


EARTH FAULTEARTH FAULT

STATOR FAULTS

DEPENDS ON HOW THE GENERATOR IS EARTHED


EARTHING OF GENERATORS

GENERATOR NEUTRAL IS EARTHED

- for stator protection- for operator safety


EARTHING OF GENERATORS – DIRECT EARTHING

Stator Windings

RELAY


EARTHING OF GENERATORS – IMPEDANCE EARTHING

Stator Windings

TYPES OF IMPEDANCES

• RESISTOR (CURRENT BASED PROTECTION)B) TRANSFORMER (VOLTAGE BASED PROTECTION)C) TRANSFORMERD) (CURRENT BASED PROTECTION)


EARTHING OF GENERATORS – RESISTANCE EARTHING

Stator Windings

CURRENTRELAY


EARTHING OF GENERATORS – TRANSFORMER EARTHING (VOLTAGE BASED)

Stator Windings

VOLTAGE RELAY


EARTHING OF GENERATORS – TRANSFORMER EARTHING (CURENT BASED)

Stator Windings

CURRENT RELAY


EARTHING OF GENERATORS – TRANSFORMER EARTHING (OPEN DELTA)

Stator Windings

VOLTAGE RELAY

OPEN DELTA PT

VOLTAGE RELAY

EARTH FAULTEARTH FAULT

STATOR FAULTS

WHEN A FAULT OCCURES CLOSE TO NEUTRAL,WITH IMPEDANCE GROUNDING, THE E/F CURRENT MAY BE LESS THAN THE PICK UP THRESHOLD OF THE NORMALE/F RELAY OR DIFFERENTIAL RELAY

STATOR EARTH FAULT

95% EARTH FAULT NORMAL RELAY

100% EARTH FAULT SPECIAL RELAYSENSES ABSENCEOF 3RD HARMONICS


STATOR EARTH FAULT0 %

95%95 TO 100%



EARTHING OF GENERATORS – (Close to neutral faults)

Stator Windings

CURRENTRELAY

a If

V

If = aV / R

100% STATOR EARTH FAULT


Measurement of third harmonic voltageacross the earthing impedance

Use of low frequency voltage injectionbetween star point & earth

LOSS OF FIELD IN GENERATORS

GENERATOR WILL OVER SPEED & OPERATE AS AN INDUCTION GENERATOR(OVER SPEEDS OF THE ORDER OF 2 TO 5% )

GENERATOR WILL CONTINUE TO DELIVER POWERWILL DERIVE EXCITATION FROM THE SYSTEM

STATOR CURRENT WILL BE 200%THERE WILL BE HEAVY ROTOR CURRENTRESULTS IN OVER HEATING



PHASE ANGLE BETWEEN

ANGLE VOLTAGE & CURRENT

IMPEDANCE REPLICA OF ANGLE PHASE ANGLE

= 360O -



I

Z


= 0o (360O) FORWARD RESISTIVE = +30o FORWARD RESISTIVE + FORWARD CAPACITIVE = +60o FORWARD RESISTIVE + FORWARD CAPACITIVE

= +90o FORWARD CAPACITIVE (LOSS OF FIELD)

= +120o REVERSE RESISTIVE + FORWADRD CAPACITIVE = +150o REVERSE RESISTIVE + FORWARD CAPACITIVE = +180o REVERSE RESISTIVE

= +210o (-150O) REVERSE RESISTIVE + FORWARD INDUCTIVE = +240o (-120O) REVERSE RESISTIVE + FORWARD INDUCTIVE

= +270o (-90O) FORWARD INDUCTIVE

= +300o (-60O) FORWARD INDUCTIVE + FORWARD RESISTIVE = +330o (-30O) FORWARD INDUCTIVE + FORWARD RESISTIVE


R

X

Z

LOSS OF FIELD

NORMAL

LOSS OF FIELDPROTECTION


R

X

Z

LOSS OF FIELD

NORMAL

K1

K2

LOSS OF FIELDPROTECTION


REVERSE POWER GENERATORS

GENERATOR WILL BECOME MOTOR

HARMFUL TO THE PRIME MOVER

( STEAM TURBINE WILL OVER HEAT)(DIESEL ENGINE WILL EXPLODE DUE TO UNBURNT FUEL)(HYDRAULIC TUBINE WILL HAVE CAVITATION)


INADVERTANT ENERGISATION

- APPLICATION OF FULL VOLTAGE AT STANDSTILL

COASTING TO STOPBEFORE SYNCHRONISM

- PRESENCE OF UNBALANCE VOLTAGE DUE TO FLASH OVER AT IONE OR TWO POLES OF BREAKER

GENERATOR FORCED TO START AS INDUCTION MOTOR RESULTING IN MECHANICAL DAMAGES TO PRIME MOVER AND EXCESSIVEHEATING IN THE ROTOR


V/Hz PROTECTION

- INCORRECT VOLTAGE REGULATOR ACTION- LOAD THROW - OFF- SUDDEN OVER VOLTAGE / OVER FREQUENCY

RESULTS IN OVER FLUXING OF GENERATORAND OVER HEATING


GENERATOR PROTECTION PACKAGESGENERATOR PROTECTION PACKAGES

CURRENT

MC11MC61AMC61C

IM30GIM3G-V

VOLTAGE

MV11MND11MVP-01

DIFFERENTIAL

MD32-GSC14S

ROTOR

UBO/CR

SYNCHRONISING

SCM21 / SPM21

ISLANDING

UFD34UM30MW33

LOAD SHEDDING

UFD34MW33MX7/5REX-8

LOAD SHARING

RRS

-

BC1 BC2

B1 B2 B3

G1 G2 G3

PT1 PT2 PT3

CT1 CT2 CT3

BUS-1 BUS-2 BUS-3

PULSES FORGOVERNOR &EXCITER



LOAD SHARING OF GENERATORS

LSR = LOAD SHARING RELAY

Fig. -1

LSR

LSR

LSR

LSR

LSR

LSR

GRID ISLANDING SCHEME

REVERSE POWER RELAYLOW FORWARD POWER RELAYUNDER VOLTAGE RELAYDIRECTIONAL O/C + E/F RELAY

dF/dT RELAYUNDER FREQ. RELAYOVER FREQ. RELAYVECTOR SURGE RELAY

DG

GRID INCOMERTRANSFORMER

PLANTLOADS

Fig. -2

SYNCHRONISATION OF GENERATORS

SYNCHRONISING IS THE PROCESS OFELECTRICALLY CONNECTING TWO AC POWER SOURCES WITHROTATING MACHINES

WITHOUT ANY DISTURBANCE TOEXISTING SYSTEM AND

WITHOUT ANY DAMAGE TO THEEXISTING SYSTEM

SYNCHRONISATION

SINGLE GENERATOR TO A BUS(DEAD BUS / LIVE BUS SYNCH.)

MULTIPLE GENERATORS TO A BUS(SIZE, VINTAGE, RESPONSE TIMES)

AUTO CHANGEOVER IN BUS CONNECTIONS

MANUAL & AUTO SYNCHRONISATION

REVERSE SYNCHRONISATION

PARAMETERS GOVERNINGSYNCHRONISATION :

VOLTAGE

FREQUENCY

PHASE ANGLE

B1 B2

G1 G2

PT1 PT2

COMMON BUS

SYNCHRONISING OF GENERATORS

SCM 21

RESULTS OF INCORRECT SYNCHRONISATION

FREQUENCY ACTIVE POWER FLOW HIGH FREQ. TO LOW FREQ.

PHASE ANGLE JOLT TO THE SYSTEMFATIGUE TO SHAFTDAMAGE TO BEARINGSOVER HEATING OF STATOR

VOLTAGE REACIVE POWER FLOWHIGH VOLTAGE TO LOW VOLTAGE

TYPES OF SYNCHRONISING RELAYS

CHECK SYNCHRONISING RELAY

AUTO SYNCHRONISING RELAY

ADJUSTABLE SETTINGS FOR F, V, MINIMUM V,F FOR CB CLOSUREDEAD BUS / DEAD LINE SELECTIONCB CLOSURE ONLY IF IS DECREASINGBREAKER OPERATING TIMEMINIMUM RECLOSING TIME2LINE + 1 BUS CONFIGURATIONU/V + O/V PROTECTION

SYNCHRONISING TROLLEY

CHECK SYNCHRONISING RELAY

AUTO SYNCHRONISING RELAY AUTO SYNCHRONISING RELAY

IN ADDITION TO SCM21 FEATURES:

INC / DEC PULSES FOR GOVERNORINC / DEC PULSES FOR AVRADJUSTABLE PULSE WIDTHPULSES PROPORTIONAL TO F, VKICKER PULSE CONTROLANTI MOTORING CONTROL

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