Generator Protection

GENERATOR PROTECTION

ENGINEERING Knowledge Management System

ELECTRICAL ENGG.

Key Words

:

Stator Protection, Relay Grouping, CT Parameters, Lead Resistance, Fault Stability, Differential Protection.

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

5/1/2007

Generator protection By PRAMOD KUMAR

DGM NTPC

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 FAULT/ABN ML CONDN

EFFECT

PROTECTION

Thermal over loading

Over heating of stator wdg/insulation failure

Thermo couples/ Over current relays

External fault

Unbalanced loading stress

Over load/negative phase sequence relay

Stator faults ph to ph/ Ph to E Inter turn

Wdg burn out Welding of core lamination

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

Rotor fault

Damage to shaft/bearing

2 stage rotor E/F protection

Motoring

LFPR/Rev power Inter lock

O/V,O/F,U.F Insulation failure,Heating of core failure of blades

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

Loss of field

Loss of field

Induction gen operation Absorb MVAR from system/damage to rotor wdg

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 power to auxiliary plant.

Generator grounding practices

Generator grounding practices

Generator grounding practices

Generator grounding practices

Generator earthing practices

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 • Trips only HV CB

Typical gen prot sld

Typical Generator protection scheme

RELAY GROUPING. PROTECTION FUNCTION 1.

2.

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

3.

Generator Transformer Earth Fault protection

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

6.

Restricted (64RGT)

7.

DUPLICATED (40G1/2 ).

8.

Back up Impedance Protection, 3 pole (21G) along with suitable timer for Coordination with line protections Backup Earth Fault Protection on Generator Transformer H V neutral (51NGT)

9.

Loss of field protection

REMARK ON GROUPING OF PROTECTION 87 G AND 87 GT SHALL BE ON TWO DIFFERENT CHANNELS OF PROTECTION.

64RGT SHALL BE IN A DIFFERENT CHANNEL THAN 87 GT 64 G1 AND 64 G2 SHALL BE ON TWO DIFFERENT CHANNELS OF PROTECTION.

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

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.

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

7.

8.

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

37/32 G1 AND 37/32 G2 SHALL BE IN TWO DIFFERENT CHANNELS OF PROTECTION

Over Flux FUNCTION (99) SHALL BE IN A DIFFERENT CHANNEL THAN O/V AND U/F FUNCTIONS

RELAY GROUPING 1.

Generator Pole slipping protection

2.

Generator interlocks

3.

Unit Transformer Differential Protection, 3 pole (87UT)

4.

5. 6.

under

voltage

relay

for

87 UT & 51 NUT CAN BE Unit Transformer LV back-up earth fault IN ONE CHANNEL AND 64 UT LV & 51UT SHALL protection BE IN ANOTHER ( 51NUT). CHANNEL. Unit Transformer LV REF (64 UT LV) Unit transformer back -up over current protection (51UT).

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 CURRENT.)

EARTHING

(E/F NOT COVERED DUE TO RESULTING IN LOW E/F

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) Typical setting 5- 7.5% of rated current.

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.

CT CONNECTION

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.

CT CONNECTION

Biased Differential protection Modern numerical relays have flexible settings for Id, b (point of slope change) and the slopes.

Typ bias setting: 10% of rated current.

EFFECT OF STATOR E/F

• 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 3RD 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% SEF PROT (3RD HARMONICS PRINCIPLE)

100% SEF PROT (3RD HARMONICS PRINCIPLE)

100% STATOR EARTH FAULT PROT (LOW FREQ.INJECTION PRINCIPLE)

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 • SETTING IS 5% OF FIELD VOLTAGE

ROTOR E/F PROT

(contd)

§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

relay accessory

FIELD NGT

COMPARISION BETWEEN E/F PROTECTIONS

INTER 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 DELAY.

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 • •

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 = I22X T TYP FOR 500 MW PERMISSIVE NEG SEQ CURRENT = 5 – 8 % OF STATOR CURRENT PERMISSIVE I22X T = 5 – 10 SETTINGS ADOPTED FOR NTPC I2 = = 7.5 % I22XT = 8.3

NEGATIVE SEQUENCE PROTECTION

Negative sequence protection

TYPICAL NPS CAPABILITY

TYPICAL NPS SETTINGS

Loss of field protection

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 FIELD

LOSS OF EXCITATION CHARACTERISTICS FOR VARIOUS TYPE OF MACHINES.

BIG M/C WITH GOOD AVR

SMALL MACHINES

POWER CHART

RELAY LINE

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 FORWARD: ZT+Z SYS, REVERSE : GEN XD’ OVER CURRENT SETTING TYP 115% DISTANCE BETWEEN THE BLINDERS = HALF OF VECTOR SUM OF ZG,ZT,ZSYS (APPROXIMATELY) TIME TYP 50-55 MSEC

TYPICAL OUT OF STEP/POWER SWING LOCUS

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 U/V 70%

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 • TIME SETTING 1.5 –2 SEC

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

Rev power/ LFPR INTERLOCK

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 TO BE COORDINATED WITH DISTANCE PROT ZONE 3

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 – SET TO 5%-7% IN HIGH IMP EARTHING

COMMONLY USED GEN/GEN TRFR RELAYS PROTEC TION

ALSTOM

ABB

SIEMENS

HIGH IMP DIFF

CAG 34 MICOM P343

RADHA REG 216

BIASED DIFF

MBCH MICOM P 633

RADSB RET 316

7 UT

POWER RELAYS

RXPE

PPX

7 UM SERIES

Directional power relays

LOSS OF FIELD

YCGF

RAGPC(DI R O/C+U/V)

7UM SERIES

Impedance / admittance

100% E/F

PVMM MICOM P343

GIX REG 216

PG871

7UE22 7UM SERIES

Low frequency injection type preferred over 3 rd harmonic principle

95% E/F

VDG

7UM SERIES

Open delta of gen sec VT

BACK UP IMP

RAKZB YCG15 MICOM SERIES REG

7UM 516

Minimum impedance

7UM SERIES

REMARK In case of duplicated diff, one low imp & one high imp preferred For trfr biased relay preferred

PROTEC TION

ALSTOM

ABB

SIEMENS

Remarks

OVER FLUXING

GTTM

RATUB RALK

7RW

IDMT

POLE ZTO+YTG SLIPPING M15

RXZF+RXPE

7UM 516

IMPEDANCE IMP+ DIR O/C IMP+NO OF POWER SWINGS

ACC. BACK ENERG

CTIG

RAGUA

7UM SERIES

O/C +CB AUX CONTACT CURRENT ELEMENT+U/V

INTER TURN

VDG MICOM

REG

7UM SERIES

comp of open delta 0n gen term+ngt sec voltage

NEG PH SEQ

CTN

RARIB

7UM SERIES

MEASUREMENT OF

REF

CAG/FAG

RADHD

7UM SERIES

ROTOR E/F

VDG MICOM SERIES

REG SERIES

7UR 22 7 UM SERIES

I2 HIGH IMP PREFFERED

Type of fault

Protection

Channel

Short circuit

87 G1 87G2 87 GT

1 2 1&2

Stator Earth Fault

64G1 64G2

1 2

Inter turn

95G

1 &2

unbalance

46G

1&2

Over load

51G

Alarm

Loss of excitation

40G1 40G2

1 2

Out of step

98G

1&2

Motoring

32 G1/2 / 37 G1/G2

1/2

O/V,O/F U/F

59/99 81G1/81G1

1 /2 1/2

System back up

21G

1&2

Accidental energisation

50GDM

1 &2

Rotor E/F

64F

1 &2

Recommenda tion

>100 MW

Generator transformer/unit transformer protections

Fault

Device no

channel

Short ckt (GT)

87T 87 HV 51 GT

1 2 2

Earth Fault(GT)

51 NGT 64GT(3 Ph GT) 64T

1 1 1/2

Short circuit(UT)

87 UT 51UT

1/2 1/2

Earth Fault UT

51 NUT 64 UT

1 2

Recomm endation

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 SCHEMES

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. • NOT CONNECTED TO THE GRID.

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 {2 ON ONE BUS CVT (ON 2 CORES) & 1 ON OTHER BUS CVT}

TYPICAL SWYD SLD • 5

17

8

R2

20

R2

181 F 18

6 4

3

7

9

16

10

12

13

19 21

15

1 281 F

2

381 F

11

14

481F

581F

681F

TYPICAL ISLANDING LOGIC FOR SELECTED BUS CVT

TYPICAL ISLANDING LOGIC FOR NON SELECTED BUS CVT SUPPLY

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 NTPC