Generator Protection

GENERATOR PROTECTION

ENGINEERING

Knowledge Management System

ELECTRICAL ENGG.

Key Words

:

Presentation by : Pramod Kumar, DGM(PE-Elect),CC, 9868390543, [email protected]

Generator protection

By

PRAMOD KUMAR

Classification of Generator

protection

Stator Protection

Abnormal operating conditions System back up protections Rotor protection

GT protections UT protections

Over view of type of fault Vs protection

O/V relay Volt/Hz relay U/F relay

Insulation failure,Heating of core failure of blades

O/V,O/F,U.F

LFPR/Rev power Inter lock Motoring

Loss of field Induction gen operation

Absorb MVAR from

system/damage to rotor wdg Loss of field

2 stage rotor E/F protection Damage to shaft/bearing

Rotor fault

Differential prot

100% E/F prot/95% E/f Inter turn prot

Wdg burn out

Welding of core lamination Stator faults

ph to ph/ Ph to E

Inter turn

Over load/negative phase sequence relay

Unbalanced loading stress External

fault

Thermo couples/ Over current relays Over heating of stator

wdg/insulation failure Thermal over loading PROTECTION EFFECT FAULT/ABN ML CONDN

GCB/NON GCB SCHEMES

•

A)

Unit scheme:

(NON GCB SCHEME)

•

In this scheme

no

switchgear is provided

between the generator and

generator transformer, which

are treated as a unit; a unit

transformer is tapped off the

interconnection for supplying

of power to auxiliary plant.

GCB SCHEME

B)

Generator circuit breaker

scheme:

In this scheme a generator

circuit breaker is provided

between the generator and

generator transformer. unit

transformer is tapped off before

the GCB for supplying of

TRIP LOGIC OF GENERATOR PROTECTION

•

TWO INDEPENDENT CHANNELS WITH INDEPENDENT

CT/VT INPUTS/DC SUPPLY/TRIP RELAY

CLASS A TRIPS

• ALL ELECTRICAL TRIP

• TRIP TURBINE , FIELD, GENERATOR,GT,UT

CLASS-B TRIP

• MECHANICAL TRIPS

• AVOID OVER SPEEDING OF TURBINE DUE TO STEAM ENTRAPPED IN TURBINE. TURBINE TRIP SIGNAL IS GIVEN FIRST AND THE ACTIVE POWER, SENSED BY THE LOW FORWARD RELAY (32G) GIVES THE TRIP SIGNAL TO THE UNIT BREAKER & FIELD BREAKER AFTER A TIME DELAY.

• IN GCB SCHEME, ONLY GCB AND FIELD IS TRIPPED,KEEPING UAT CHARGED THROUGH GT

• IN NON GCB SCHEME, HV CB,FIELD,UT LCV CB ARE TRIPPED.

• Class C

Typical Generator

protection

scheme

RELAY GROUPING.

PROTECTION FUNCTION REMARK ON GROUPING OF PROTECTION

1. Generator Differential Protection, 3 pole (87 G) having operating time of 25 milli sec. or lower at five times the current rating.

2. Overall Differential Protection (87GT).

87 G AND 87 GT SHALL BE ON TWO DIFFERENT CHANNELS OF

PROTECTION. 3. Generator Transformer Restricted

Earth Fault protection (64RGT)

64RGT SHALL BE IN A DIFFERENT CHANNEL THAN 87 GT

4. Stator Earth Fault Protection covering 100% of winding (64G1), operating on low frequency signal injection principle suitable for continuous monitoring of stator insulation even during machine shut down.

5. Stator Standby Earth Fault Protection covering 95% of winding (trip) (64 G2) with adjustable time delay

64 G1 AND 64 G2 SHALL BE ON TWO DIFFERENT CHANNELS OF

PROTECTION.

6. Inter-turn Fault Protection (95G1), through comparison of zero sequence voltage on generator phase and neutral side.

7. DUPLICATED Loss of field protection (40G1/2 ).

40G1 AND 40 G2 SHALL BE ON TWO DIFFERENT CHANNELS OF PROTECTION.

8. Back up Impedance Protection, 3 pole (21G) along with suitable timer for Co-ordination with line protections

9. Backup Earth Fault Protection on Generator Transformer H V neutral (51NGT)

21 G AND 51 NGT BE IN DIFFERENT CHANNELS

RELAY GROUPING

1. Negative Sequence Current Protection, alarm and I 22t element for trip (46G) matching with the machine

characteristics.

2. Duplicated Low -Forward Power / reverse power Interlock for steam turbine generator (37 /32G1 & 37/32 G2), each having two stages, short time delayed interlocked with turbine trip and long time delayed independent of turbine trip.

37/32 G1 AND 37/32 G2 SHALL BE IN TWO

DIFFERENT CHANNELS OF PROTECTION

3. Two Stage Rotor Earth Fault Protection (alarm & tri p) operating on principle of continuously monitoring rotor insulation value even during machine shut down period (64F).

4. Definite Time Delayed Over -Voltage Protection (59G) for alarm and trip.

5. Generator Under Frequency Protection with alarm and stage tripping (81G)

with df/dt elements.

6. Over Fluxing Protection (99) for Generator / Generator Transformer having inverse time characteristics suitable for Generat or /Generator Transformer over fluxing capability.

Over Flux FUNCTION (99) SHALL BE IN A

DIFFERENT CHANNEL THAN O/V AND U/F FUNCTIONS

7. Accidental Back Energisation protection for accidental closure/flashover of EHV breaker or EHV disconnecting switch (50GDM)

8. Instantaneous and time delayed Over Current protection to be used on H V side of excitation transformer.

RELAY GROUPING

1. Generator Pole slipping protection

2. Generator under voltage relay for interlocks

3. Unit Transformer Differential Protection, 3 pole (87UT)

4. Unit Transformer LV back-up earth fault protection

( 51NUT).

5. Unit Transformer LV REF (64 UT LV) 6. Unit transformer back -up over current

protection (51UT).

87 UT & 51 NUT CAN BE IN ONE CHANNEL AND 64 UT LV & 51UT SHALL BE IN ANOTHER

CHANNEL.

DUPLICATED PROTECTIONS TO BE CONNECTED TO

TRIP RELAYS OF RESPECTIVE GROUPS .SINGLE

PROTECTION TO BE CONNECTED TO TRIP RELAYS OF

BOTH THE GROUPS.

GENERATOR PROTECTIONS IN DETAIL

DIFFERENTIAL PROTECTION

COVERS PHASE FAULTS

HIGH IMPEDANCE EARTHING RESULTING IN LOW E/F CURRENT.)

EFFECTS:

• HIGH CURRENTS

• POTENTIAL DAMAGE TO MACHINES

• EXPENSIVE OUTAGE/REPAIR DUE TO DAMAGE.

FEATURES:

• UNIT TYPE PROTECTION

• INSTANTANEOUS IN OPERATION.

• COVERS THE STATOR WDG FOR PHASE TO PHASE FAULTS. • DUPLICATED DIFFERENTIAL PROT GIVEN USED FOR GCB

SCHEME

• TWO TYPES: HIGH IMPEDANCE TYPE/BIASED TYPE. • STABLE FOR THROUGH FAULTS.

HIGH IMP TYPE RELAY contd

• CT PARAMETERS

Vk = 2 If (Rct+2Rl)

Vk – Min. Knee point voltage of the CT

If - Maximum fault current in the system

(converted to sec side)

Rct- Secondary resistance of the CT

Rl – lead resistance of the sec connection

(typ 8.73 ohms per km for 2.5 sq mm cu cable)

HIGH IMPEDANCE TYPE DIFF RELAY

• USE TWO SETS OF IDENTICAL DEDICATED CTs

• PS CLASS CTs WITH STRINGENT PARAMETERS TO BE USED

• TWO CTs PARALLED OUT SIDE THE RELAY AND SINGLE INPUT TO THE RELAY • VERY SENSITIVE

• THROUGH FAULT STABILITY ACHIEVED BY USING STABILISING RESISTORS IN THE RELAY CIRCUILT.

BIASED TYPE DIFF RELAY

• CTS CAN BE SHARED WITH OTHER PROTECTIONS • PS CLASS CTs REQUIRED.

• LESS STRINGENT CT PARAMETERS.

• INDIVIDUAL CT INPUTS GIVEN TO THE INDIVIDUAL BIAS COILS. • THROUGH FAULT STABILITY ACHIVED THROUGH BIASING.

• CT MISMATCH (TYP OF THE PRDER OF 1:5 ) CAN BE ACCOMODATED. • MORE SUITABLE FOR NUMERICAL INTEGRATED PROTECTION SYSTEMS

AS THE CTs CAN BE SHARED FOR MANY FUNCTIONS.

Biased Differential protection

Typ bias setting: 10% of rated current.

Modern numerical relays have flexible settings for

Id, b (point of slope change) and the slopes.

• STATOR EARTH FAULT PROTECTION

• E/F CURRENT IS LIMITTED TO 10A

• THIS MINIMIZES THE DAMAGE

• FIRST FAULT LESS CRITICAL

• NEEDS CLEARANCE AS

IT MAY DEVELOP INTO A PH TO PH FAULT

SECOND FAULT WILL RESULT IN VERY

HIGH CURRENT

• TWO TYPES:

• 100 % E/F

• 95 % E/F

• 95 % SEF

• RESULTS IN VOLTAGE SHIFT OF GEN NEUTRAL

W.R.T GROUND

• DETECTED BY VOLTAGE RELAY CONNECTED

ACROSS GROUNDING RESISTOR OR FROM

THE GENERATOR TERMINAL THROUGH OPEN

DELTA VT

• PROTECT APPROX 95% OF STATOR WDG

• TYP SETTING:

– For IDMT type relays

– Minimum tap

– TIME DELAY OF MORE THAN 1 SEC

(GEN IDMT RELAY WITH PMS 5.4 AND TMS 1 USED) – For Def time delay type: 5%of 110 V ie, 5.5 V at 1 sec

100 % Stator E/F Protection

THIRD HARMONIC PRINCIPLE

– A RELAY WHICH RESPONDS TO THE REDUCTION OF

THE 3

_{HARMONIC COMPONENT}

– A STATOR PHASE-TO-GROUND FAULT OCCURS AT OR

NEAR THE GENERATOR NEUTRAL, THERE WILL BE AN

INCREASE IN THIRD HARMONIC VOLTAGE AT THE

GENERATOR TERMINALS, WHICH WILL CAUSE RELAY

OPERATION.

– DISADVANTAGES

DUE TO DESIGN VARIATIONS, CERTAIN GENERATING

UNITS MAY NOT PRODUCE SUFFICIENT THIRD

HARMONIC VOLTAGES

THIS METHOD DOES NOT PROTECT THE M/C DURING

STAND STILL CONDITIONS.

100% SEF BASED ON THIRD HARMONICS

MEASUREMENTS

100% STATOR EARTH FAULT PROT

100 % stator E/F protection

•

SETTINGS TYP FOR 500 MW UNIT

• Trip : 10 Ohm / 1 sec

• Alarm : 20-30 ohm /10 sec

• SETTINGS ARE TO BE FINALISED

DURING COMMISSIONING TEST IN

LINE WITH INSTRUCTIONS OF RELAY

CATALOGUE.

ROTOR EARTH FAULT PROTECTION

•

FIRST ROTOR E/F DOES NOT CAUSE IMMEDIATE

DAMAGE

•

SECOND E/F RESULTS IN A WDG SC OF ROTOR

•

CAUSE MAGNETIC UNBALANCE/MECH FORCES

/DAMAGE

•

METHODS OF DETECTION

– POTENTIOMETER METHOD

• A CENTRE TAPED RESISTOR IS CONNECTED ACROSS THE MAIN FIELD WINDING

• THE CENTRE TAP IS CONNECTED TO EARTH THROUGH A VOLTAGE RELAY

• AN EARTH FAULT ON THE FIELD WINDING WILL PRODUCE VOLTAGE IN THE RELAY, MAXIMUM VOLTAGE OCCURRING FOR END FAULTS

• A BLIND SPOT EXISTS AT THE TAPPING POINT, TO AVOID THIS , THE TAPPING POINT IS VARIED WITH A PUSH BUTTON OR SWITCH , AND IS TESTED PERIODICALLY TO DETECT BLIND ZONE

§LOW FREQUENCY INJECTION METHOD

MODERN ROTOR EARTH FAULT PROT ECTION

RELAY OPERATES ON THE PRINCIPLE OF LOW

FREQUENCY INJECTION INTO THE FIELD

WINDING VIA CAPACITORS.

CORRESPONDING CURRENT OR RESISTANCE

DURING E/F IS SENSED

TYP SETTING (500 MW)

ALARM 40 K OHM TIME = 10 SEC

TRIP 5 K OHM TIME = 1 SEC

ACTUAL VALUES OF SETTING SHALL BE DECIDED AT

SITE DURING COMMISSIONING TO ACCERTAIN THE

HEALTHY VALUE OF THE PARTICULAR M/C.

SEF/REF USING INJECTION PRINCIPLE

TYPICAL CONNECTION

TYPICAL CONNECTION DIAGRAM OF SEF/RF

USING INJECTION PRINCIPLE

NGT

FIELD

I

NTER TURN PROTECTION

•

CURRENT BASED SYSTEM

• FOR GENERATORS WITH SPLIT NEUTRALS WITH ALL SIX TERMINALS BROUGHT OUT ON NEUTRAL SIDE

• DELAYED LOW-SET O/C RELAY WHICH SENSES THE CURRENT IN THE CONNECTION BETWEEN THE NEUTRALS OF THE STATOR WINDINGS

•

VOLTAGE BASED SYSTEM

RELAY COMPARES THE NEUTRAL NGT SEC VOLTAGE AND GEN TERMINAL OPEN DELTA VOLTAGE

BALANCE DURING E/F OR NORMAL CONDITION

DURING INTER TURN FAULT OPEN DELTA VOLTAGE WILL BE DEVELOPED AND NGT SEC VOLTAGE WILL BE ZERO,RESULTING IN A DIFFERENTIAL VOLTAGE WHICH MAKES THE RELAY

OPERATE

IDMT RELAYS WITH 5.4 PMS AND 1 TMS ARE ADOPTED.

DEF TIME TYPE RELAYS: MINIMUM SETTING WITH I Sec

O/V PROTECTION

.

TYP SETTINGS OF A 3 STAGE O/V RELAY IS AS FOLLOWS

ALARM 110 % 2 SEC

TRIP 120 % 1 SEC

140 % INSTANTANEOUS

U/F O/F PROTECTION

TYPICAL SETTING:

U/F

O/F

ALARM - 47.8HZ 1 SEC 51 Hz 1 SEC

TRIP - 47.4 HZ 2 SEC

51.5Hz 2.5 SEC

SETTING NEED TO BE CO-ORDINATED WITH THE

RESPECTIVE GRID AGENCY AND THE ISLANDING

SCHEME SETTINGS AND THE M/C CAPABILITY.

Negative sequence protection

• NEGATIVE SEQUENCE PROTECTION FOR GENERATOR PROTECTS THE GENERATOR FROM EXCESSIVE HEATING IN THE ROTOR RESULTING FROM UNBALANCED STATOR CURRENTS

• CAUSED DUE TO

– ONE POLE OPEN IN LINE

– ONE POLE OPEN OF A CIRCUIT BREAKER – CLOSE IN UNCLEARED UNBALANCED FAULTS

• THE NEGETIVE SEQUENCE PROTECTION RELAYS SHALL BE SET TO THE NPS CAPABILITY OF THE MACHINE WHICH IS

• K = I₂2_{X T}

• TYP FOR 500 MW

PERMISSIVE NEG SEQ CURRENT = 5 – 8 % OF STATOR CURRENT PERMISSIVE I2

2_{X T = 5 – 10}

SETTINGS ADOPTED FOR NTPC I2 = = 7.5 %

Loss of field protection

•

ACTS AS AN INDUCTION GENERATOR

•

INDUCED EDDY CURRENTS IN THE FIELD WINDING,

ROTOR BODY, WEDGES AND RETAINING RINGS

•

MW FLOW IN TO THE SYSTEM/ MVAR FLOWS IN TO THE

MACHINE.

•

THE APPARENT IMP TRAVELS TO THE FORTH

QUADRANT OF X-Y PLANE

•

METHOD OF DETECTION:

MINIMUM IMPEDANCE WITH U/V

SOME RELAYS ARE SET IN THE ADMITTANCE PLANE

MATCHING WITH THE CAPABILITY CURVE OF THE

MACHINE

TRIP CHARACTERISTICS OF

LOSS OF FIELD PROTECTION

LOSS OF EXCITATION CHARACTERISTICS FOR VARIOUS TYPE OF MACHINES. BIG M/C WITH GOOD AVR SMALL MACHINES

POWER CHART

OUT OF STEP PROTECTION

• MACHINE RUNS OUT OF SYNCHRONISM WITH THE NETWORK • CYCLIC VARIATION OF ROTOR ANGLE

• CURRENT INCREASES HEAVILY

• FREQUENCY DEPEND ON THE RATE OF SLIP • RESULT IN THE WINDING STRESS

• IT MAY ALSO DAMAGE THE AUXILIARIES OF THE AFFECTED UNIT

• DETECTED BY SENSING THE VARIATIONS IN IMP

• DISTINGUISH BETWEEN THE RECOVERABLE SWING AND THE IRRECOVERABLE SWING

– BLINDERS + A SUPERVISORY MHO ELEMENT,TRIP WHEN IMP IS INSIDE THE MHO AND CROSE THE BLINDERS WITH THE SPECIFIED TIME.

– MINIMUM IMPEDANCE(MULTIPLE ZONE) + COUNTING NO OF SWINGS

TYPICAL POLE SLIPPING RELAY

CHARACTERISTICS

TYP SETTING:

MHO RELAY SETTING

:

TYP 115%

DISTANCE BETWEEN THE BLINDERS = HALF OF VECTOR SUM OF ZG,ZT,ZSYS (APPROXIMATELY) TIME TYP 50-55 MSEC

ACCIDENTAL BACK ENERGISATION

• CAUSE:

• FLASH OVER OF THE GENERATOR BREAKER

• INCORRECT CLOSING OF THE GENERATOR BREAKER • EFFECTS

• CAUSE OPERATION AS AN INDUCTION MOTOR • DAMAGEMACHINE AND TURBINE

• THE RAPID HEATING IRON PATHS NEAR THE ROTOR SURFACE DUE TO STATOR INDUCED CURRENT.

• DETECTED BY

• OVER CURRENT + CB AUXILIARY CONTACTS

CHECKS FOR THE CURRENT WHEN THE GEN BREAKER CONTACTS ARE OPEN SET BELOW THE RATED CURRENT(90%)

• O/C AND U/V MEASUREMENTS O/C 1.2 TIMES

ACCIDENTAL BACK ENERGISATION

USING CB AUX CONTACTS & O/C

• Backup impedance protection

• FOR UNCLEARED SYSTEM FAULT

•

THE BACKUP PROTECTION IS TIME DELAYED

TO COORDINATE WITH THE ZONE 3 SETTING

OF LINES

• DETECTED BY

– OVER CURRENT

– DISTANCE

– DISTANCE PREFFERED AS THE LINE IS PROVIDED

WITH DISTANCE RELAYS

• SETTING SHOULD BE MADE TO COVER THE GT

IMP AND THE LONGEST LINE IMP

• SETTING SHOULD TAKE CARE OF THE INFEED

FROM OTHER GENERATORS CONNECTED TO

THE SAME BUS ALSO

REVERSE /LOW FORWARD

POWER INTERLOCK

LOW FORWARD AND REVERSE POWER

INTER LOCK

• To allow entrapped steam in the turbine to be

utilized to avoid damage of the turbine blade.

• To protect the machine from motoring action

• Trip under class B after a

short time

delay in

case the turbine is already tripped ( typ set at 2

sec)

• Trip under class A, after a long time delay if

turbine is not tripped (typically set at 10 sec)

• Power setting typ 0.5 % of rated power

GEN TRFR PROTECTION

• DIFFERENTIAL

BIASED DIFFERENTIAL

– 10 % BIAS SETTING (TO COVER TAP RANGE AND CT MISMATCH IF ANY)

– TIME: INSTANTANEOUS

BACK UP EARTH FAULT

DEF TIME OR IDMT RELAY 20 % WITH 2 SEC TIME DELAY

UT PROTECTION

• DIFFERENTIAL

– BIASED DIFF USED

– BIASED SETTING 10%

BACK UP OVER CURRENT

– 2-3 TIMES THE FULL LOAD CURRENT

– DELAY 0.9 SEC

– TAKE CARE OF ANY LARGE MOTOR STARTING CASE

RESTRICTED E/F

– HIGH IMP DIFF

COMMONLY USED GEN/GEN TRFR RELAYS

Open delta of gen sec VT 7UM SERIES VDG 95% E/F Minimum impedance 7UM 516 RAKZB REG YCG15 MICOM SERIES BACK UP IMP Impedance / admittance 7UM SERIES RAGPC(DI R O/C+U/V) YCGF LOSS OF FIELD

Directional power relays 7 UM SERIES PPX RXPE POWER RELAYS 7 UT RADSB RET 316 MBCH MICOM P 633 BIASED DIFF In case of duplicated diff, one low imp & one high imp preferred For trfr biased relay preferred 7UM SERIES RADHA REG 216 CAG 34 MICOM P343 HIGH IMP DIFF REMARK SIEMENS ABB ALSTOM PROTEC TION

7UR 22 7 UM SERIES REG SERIES VDG MICOM SERIES ROTOR E/F HIGH IMP PREFFERED 7UM SERIES RADHD CAG/FAG REF MEASUREMENT OF

I

comp of open delta 0n gen term+ngt sec voltage 7UM SERIES REG VDG MICOM INTER TURN O/C +CB AUX CONTACT CURRENT ELEMENT+U/V 7UM SERIES RAGUA CTIG ACC. BACK ENERG IMPEDANCE IMP+ DIR O/C

IMP+NO OF POWER SWINGS 7UM 516 RXZF+RXPE ZTO+YTG M15 POLE SLIPPING IDMT 7RW RATUB RALK GTTM OVER FLUXING Remarks SIEMENS ABB ALSTOM PROTEC TION

1 &2 1 &2 1 & 2 1 /2 1/2 1 / 2 1&2 1 2 Alarm 1&2 1 &2 1 2 1 2 1&2 Channel >100 MW Recommenda tion 95G Inter turn 64G1 64G2 Stator Earth Fault

64F Rotor E/F 50GDM Accidental energisation 21G System back up 59/99 81G1/81G1 O/V,O/F U/F 32 G1/2 / 37 G1/G2 Motoring 98G Out of step 40G1 40G2 Loss of excitation 51G Over load 46G unbalance 87 G1 87G2 87 GT Short circuit Protection Type of fault

Generator transformer/unit transformer protections

channel

Recomm

endation

Device no

Fault

Numerical integrated generator protection systems

•

Many functions in the same relay

•

Takes multiple CT/VT inputs.

•

Minimum of 2 nos to be used.

•

All the prot functions are to be divided in to 2 groups .

•

Built in DR(fast scan)/SOE functions

•

Self supervision

•

Communicable

•

Has programmable logic gates which simplifies the auxiliary circuits.

COMMON RELAYS ARE

REG series OF ABB

7UM SERIES OF SIEMENS

MICOM SERIES OF AREVA.

GENERATOR DISTURBANCE RECORDER

• RECORD THE GRAPHIC FORM OF INST.VALUES OF POWER SYSTEM QUANTITIES

• FAST SCAN (1-5 KHz) AND SLOW SCAN (5/10 Hz) FEATURES • SUFFICIENT ANALOGUE/DIGITAL INPUTS.

• TRIGGERING FROM DIGITAL INPUTS AND THRESHOLD/RATE OF CHANGE OF ANALOGUE VALUES.

• ADEQUATE MEMMORY

• GOOD FREQUENCY RESPONSE

• INDIVIDUAL ACQUISITION UNITS AND COMMOM EVALUATION UNIT FOR A STATION

Islanding scheme

n DEPENDS ON TYPE OF GENERATING SYSTEM

n GRID CONNECTED GENERATING STATIONS

• GENERATOR IS CONNECTED TO THE GRID THROUGH EHV TRANSMISSION LINES.

• CAPTIVE GENERATING STATION

• DEDICATED GENERATOR(S) SUPPLIES POWER TO A PARTICULAR UTILITY/ESTABLISHMENT.

TYPE OF ISLANDING SCHEMES.

• FOR GRID CONNECTED GENERATORS

CRITERIA:

UNDER FREQUENCY / RATE OF CHANGE OF

FREQUENCY

ACTION:

STAGGERED TRIPPING OF GRID LINES AT

PREDTERMINED LOGIC AT THE PRE DECIDED

SEQUENCE.

ISLANDING SCHEME FOR GRID

CONNECTED GENERATORS.

• KEY FEATURES

– INTEGRATED SCHEME FOR THE WHOLE

PLANT

– FREQUENCY BASED

– TRIGGERING BASED ON THRESHOLD AND

RATE OF CHANGE OF FREQUENCY

– U/F RELAYS CONNECTED TO BUS CVT

– BASED ON 2 OUT OF 3 LOGIC

– INDIVIDUAL TRIP RELAYS FOR EACH FEEDER

– STAGGERED TRIPPING SCHEME TO BE

ENGINERED IN COORDINATION WITH

RESPECTIVE GRID AGENCY DEPENDING ON

THE SYSTEM CONDITIONS AND THE POWER

NUMBER OF THE CONNECTED GRID.

CVT SUPPLY FOR U/F

RELAYS

• CONNECTED TO THE SELECTED

BUS CVT SUPPLY

OR

• DISTRIBUTED AMONG THE 2 BUS CVTS

{

TYPICAL SWYD SLD

•

TYPICAL ISLANDING LOGIC

FOR SELECTED BUS CVT

TYPICAL ISLANDING LOGIC

ISLANDING FOR CAPTIVE

GENERATING PLANTS.

• FEATURES

– BASED ON LOAD GENERATION BALANCE.

– SCADA BASED DYNAMIC LOGIC

– ADAPTIVE TO SYSTEM CHANGES

– PRIORITY GROUPS ARE SET FOR ISLANDING

– TRIPPING SEQUENCE IS DECIDED BY THE SOFTWARE

BASED ON THE PRIORITY AND THE DYNAMIC LOAD

GENERATION BALANCE.

THANK YOU