Generator Protection

MADRAS ATOMIC POWER STATION

Presented by J.ROOBY

March 2001

TURBO GENERATOR

PROTECTION

ELECTRICAL PROTECTIONS

TRIP TYPE:: TT GCB FBDIFFRENTIAL STATOR EARTH ROTOR EARTH OVERVOLTAGEOVERCURRENT UNBALANCEUNDERFREQUENCY

PROTECTIONS - 2

TRIP TYPE TT GCB FB

UNDEREXCITATION

W/O LOSS OF FIELD

WITH LOSS OF FIELD

REVERSE POWER LONG TIME

SHORT TIME

(OPERATES ONLY AT TT)

THW: ELEC. PROTECTION BHEL RECOMMENDATIONS

‘Resistor’ ground. Minimum stator earth fault protection: 95%. E/F current < 2A for 2 sec.Trip within 24 Hrs. on 1st rotor earth fault alarm On 2nd fault machine to be trippedOver-voltage relay at 120% rated. Reset factor of the relay not less than 0.95.Tripping on exceeding specified loads.Negative phase sequence: I2².t = 8 On continuous basis: I2 < 5%.

THW: ELEC. PROTECTION - 2 BHEL RECOMMENDATIONS

Loss of field protection allowed at 40% for 15 minutes etc. If grid cannot sustain on auto basis, tripping within 5 sec.Difference in any two phase currents by more than 20% shall cause instant trip.Inter-turn protection with instant tripping if out of balance current in two parallel paths exceeds 2 - 3% of rated current.

THW: ELEC. PROTECTION - 3

BHEL RECOMMENDATIONS

Back up protection for generator main breaker failure shall be provided.Operation at a frequency below 47.5 or above 51.5 Hz allowed only for a total of 2 Hrs. in entire life of set. (Turbine)Reverse power relay to be set at 0.5% of rated output with a time delay of 3 - 10 seconds.

THW : TRIPPING SCHEME PROTECTION TT GCB FB A Generator differential

Stator earth faultRotor earth fault - 1st

- 2nd

Over-voltage OverloadNegative ph seq currentInter-turn for stator wdg.Reverse powerLoss of field

THW: MECHANICAL PROTECTIONS

Bearing babbit 75° High Oil temp.,flow babbit 80° HH Trip B manual

Oil out 60° High Oil temp.,flow Oil out 65° HH Trip B manual

H2 seal-oil inlet 45°High Flow,cooler,CW outlet 70°High Trip B manual

DM Conductivity: 20µMho: Trip B AutoDM inlet temp. <39°: Reduce CW flow

44°: Cooler; Unload >48°: Trip B manual

MECHANICAL PROTECTIONS - 2

Wdg.DM flow <21M³/Hr Unload to 75% <13M³/Hr 4 mte Auto trip B

DM outlet 85° DM flow-temp,CoolerWdg. temp. 75° Unload to normalizeDiff in 2 RTDs >20° Run down,man.trip B

Cold H2 High 44°C W inlet temp,press,& HighHigh 55° Unload.Trip B manual

H2 hot gas High75° CW press,temp,flowCore temp High95° Unload,Trip B manu


H2 purity Low 95% Trip B manual

H2 press.Low -0.2bar Unchecked, trip B High +0.2bar Restore to normal

Rotor wdg.temp High115°H2 temp press HighHigh 120° Unload,Trip B

CW inlet temp Low 20° Bring it up High 37°Scheduled unload HighHigh 48° Run down Trip B


Liquid in LLI :If CW, isolate cooler,unload If seal oil, rectify,trip B manu. If DM water, check H2 press.

STATOR EARTH FAULT

Type of earthing and earth fault current value decide the relay. For resistance grounded TG, definite time or IDMT ground over current relay is used. For solid earth, an IDMT relay is preferred.For solidly / resist. grounded TGs, standby E/F relay operated off a CT is used.

STATOR EARTH FAULT - 2

Standby E/F relay backs up the differential or restricted E/F protection when provided, against internal earth faults. For resistance grounded TG,with low E/F in feeds, lower ratio neutral CT can be selected, achieving optimum sensitivity.

INDUCTION TYPE IDMT RELAY

Inverse with Definite Minimum Time characteristic relay: Has definite minimum time to operate due to self braking effect of fluxes that produce torque.

DEFINITEMINIMUMTIME

Time

Current

OVER-CURRENT RELAY INDUCTION TYPE

TRIP

Fluxes due to primary and secondary windings, separated in phase, produce a torque on disc, which is restrained by a spring. In case of over- -current,disc moves and closes the trip contacts.Time of travel and over-current settings can be

altered. CURRENT

REVERSE POWER RELAYWhen power flows normally, fluxes in windings tend to rotate disc away from trip contact. When it flows in reverse direction, torque is in opposite direction and trip contacts close.Relay is made sensitive by having a very light control spring.

TRIP

CURRENT

VOLTAGE

STATOR EARTH FAULT - 3 IDMT TYPE RELAY 64S

64S 64S

STATORWINDING

LOWRATIO CT

SOLID EARTHING RESISTANCE EARTHING

STATOR EARTH FAULT - 4RELAY 64S FOR HIGH IMPEDANCE EARTH

64S

64S

LOAD RESISTANCEDISTBN.

TRANSF.

VOLTAGE OPERATEDNEUTRAL DISPLACEMENT SENSITIVE CURRENT IDMT TYPE 5-20 V OPERATED

STATORWINDING

LR

STATOR EARTH FAULT - 4

Earth fault relay is normally used along with follower timer for a sensitive setting or 2 stage protection using 2 relays used.

1st stage with sensitive setting ~ 5% with a follower timer and second with coarser setting say 10% with instantaneous trip.

They cover 90-95% of winding. For 100%, sub harmonic voltage injection or 3rd harmonic voltage comparison based relay is used.

STATOR GROUND FAULTS SAMPTH & PRATAPKUMAR ENGLISHELECTRIC

Phase to ground fault, depending upon fault location, increases elect. stresses on unaffected winding. Probability of 2nd ground fault increases.

Serious damage may result, if a fault occurs near to neutral and is then followed by a 2nd fault higher up in same phase.

STATOR GROUND FAULTS - 2

This 2nd fault may result from insulation deterioration caused by transient over- -voltages due to erratic, low current unstable arcing of the 1st fault.

2nd fault may result in high currents.

To cover entire winding with earth fault protection, three methods are used:

1. Measurement of 3rd harmonic at generator neutral voltage.


2. Deliberate displacement of neutral potential with respect to ground, by injecting a voltage, at a sub-multiple of power frequency.

3. Comparison of 3rd harmonic voltages generated at both: neutral and line ends of the winding.

English Electric uses 3rd method.

3rd harmonic voltage builds up across capacitive impedance of phase to ground


Due to ground impedance, neutral shall also have 3rd harmonic voltage to earth.

Actual 3rd harmonic voltage is 1- 3 % of rated voltage at no load. At loads, it can be 0.5 to 2.5 times the no load value. However ‘VN3 / VL3’ remains constant.

When fault occurs at point F, VN3 / VL3 ratio changes. Difference of VN3 & VL3 as a % of V3, is sensed by relay PVMM.


There is a blind zone when the ratio VN3 / VL3 remains same in healthy as well as in fault condition. Relay shall not sense the fault. This is taken care of by the usual 95% winding coverage relay tuned to 50 Hz.Relay stability depends upon availability of both neutral and line voltages. Later can disappear if VT fuse blows.

STATOR GROUND FAULTS - 6 SAMPTH & PRATAPKUMAR ENGLISHELECTRIC

VT fuse health is monitored by a circuit consisting of a reed relay which gets energized if the fuse fails.

STATOR GROUND FAULTS - 7 SAMPTH & PRATAPKUMAR, ENGLISHELECTRIC

N L 0 0.2 0.6 1.0 FAULT POSITION

VL3VN3

BLIND ZONE

BLIND ZONE

N LF

Q: HEALTHYF: FAULTY

V3N L

RnVN3

VL3

V3

VN3VL3

VN3VL3

V3

VN3F

VN3Q

VL3FVL3Q

STATOR GROUND FAULTS - 8 SAMPTH & PRATAPKUMAR, ENGLISHELECTRIC

G

NEUTRAL DISPLACEMENTDETECTOR UNIT

3rd HARMONIC VOLTAGE COMPARATOR

GROUNDTRANSFORMER

LINE PT

PVMM RELAY INPUTS

GENERATOR DIFFERENTIAL

It is a unit protection, covering both phase and earth faults within machine. Protection zone is defined by CTs on neutral and line sides of stator winding.High impedance type protection, off CTs having identical ratio and rating used. CTs are low reactance type class PS with minimum turns ratio error and of identical magnetizing characteristics.

GENERATOR DIFFERENTIAL - 2

The relays are either current or voltage calibrated & tuned to system frequency to ensure stability on through faults in presence of 3rd harmonic currents and transient DC offsets in fault current.


87

87

87

RESISTORS

HIGH IMPEDANCERELAY

STATOR WDG.


64

64

STATOR WDG.RYBN

ADDL. CT IF EARTHING TAP OFF IS BEFORE THENEUTRAL CT


T

87

CT AACTIVE

CT BSATUR.

RST RCT

IS

VS

RL Lead Resistance

If/n

If

• Max. Vs that can appear under thro’ fault = If/n {RCT+2RL}Relay voltage setting to be >Vs.For current relay, choose RST

such that Is remains below relay setting.• CTs to have a knee point voltage >2Vs to ensure that current thro’ relay is > twice the setting current when internal fault occurs for fast & positive operation of the relay.

CT A (n/1) CT B (n/1)

87

GENERATOR DIFFERENTIAL - 6Associated CTs should have a knee point voltage of at least twice the setting voltage Vs, to ensure that the CTs push at least twice the setting current thro’ the relay on internal fault for fast and positive operation.Knee point voltage Vk of the CT is:

Vk => 2 Vs or Vk => 2 If/n { RCT + 2RL}


Associated CTs will see current inrush into Generator for an internal fault. This results in high peak voltage across relay and CT secondary pilots. This value may exceed 3 KV, so it is customary to use nonlinear resistors (Metrosits) across relay branch to limit such voltages within limits.

GENERATOR DIFFERENTIAL - 8 BIASED DIFFERENTIAL RELAY

Biased differential relay is used when TG +GT are treated as single zone. Y GT is compensated by Y CT connection.For unit auxiliary transformers, CTs are provided on UAT tap off.

CT

Y

87

YY

G T Y

UATET Y

INTERPOSING CT

UNBALANCED LOADING SH Y. K. PANDHARIPANDE NASIK 1999

Unbalanced loads in TG cause negative sequence currents to flow. These create synchronous field in reverse direction.This field produces 2f (100Hz) currents to flow on rotor surface & intense heat.Negative sequence relay give alarm if I2 increases preset value and trip the m/c if I2²•t exceeds limit. Alarm is set at 80% of I2²•t trip value and instant trip at 100%

46

ZB ZR

R

Y

B

UNBALANCED LOADING NEGATIVE SEQUENCE RELAY ‘46’

IR

VR

IYIB VB

IB IR

VR + VB = 0 IR

VR

IB

IY

VR + VB

VB

ROTOR EARTH FAULTFirst or single rotor earth fault is detected based on DC injection principle. This method requires access to field circuit.For brushless exciters often instrument slip rings are provided to which relay can be connected.Relay is time delayed and mostly made to initiate alarm. It can detect fault even during machine standstill condition.

ROTOR EARTH FAULT - 2

ExAUX ACSUPPLY

RELAY FIELDWINDING

+

-

ROTOR EARTH FAULT - 3 SH Y K PANDHARIPANDE, NASIK JUL 1999

If first earth fault appears, it is essential to protect rotor from second earth fault damage which is severe.This is brought in service in steps using 4 position selector switch. Relay is based on disturbed bridge balance which appears on first fault. By adjusting on a potentiometer, bridge is balanced. 2nd fault shall flow current thro’ 64R2 to trip.

ROTOR EARTH FAULT - 4 SH Y K PANDHARIPANDE, NASIK JUL 1999

ExAUX ACSUPPLY

+

-

+

TRIP

1st E/FBalanceTest2nd E/F

64R2 mA

POTENTIOMETER

2nd

1st

64R1

1st ROTOR EARTH FAULT

ExAUX ACSUPPLY

+

-

1st E/F

POTENTIOMETER

E/F

ACA - PROT - 48 / 80

64R1

•Bridge gets unbalanced.•Relay 64 R1 gets signal.•Alarm is initiated.

BALANCE POSITION

ExAUX ACSUPPLY

+

-

+

mA


POTENTIOMETER

1st E/F

64R1

mA HAS NO CURRENT

TESTING FOR BALANCE

ExAUX ACSUPPLY

+

-

+

TRIP

1st E/FBalanceTest

64R2 mA

POTENTIOMETER

1st

64R1

2ND ROTOR EARTH FAULT

Ex

+

-

+

TRIP


64R2 mA

POTENTIOMETER

2nd

1st

RELAY 64 R2 GETSOUT OF BALANCECURRENT & INITIATESTRIPPING

FIELD FAILURE PROTECTION SH Y K PANDHARIPANDE, NASIK JULY 1999

Failure of brushgear,accidental opening of FCB, failure of AVR cause field loss.

Two types of relays used: Under current type and Offset MHO relay.

Under current relay, set at <8% If, that is < min. field current, is used with follower timer. To overcome slip freq. currents OFF delay and ON delay timers used.

Unsuitable for large TGs - Ifo is small.

E

50

ALARM / TRIP

FCB

D.R.

FIELDWINDG.

EXCITATION

50:FIELD UNDER CURR RELAYT1 OFF DELAY TIMER 0.1-1ST2 ON DELAY TIMER 0.1-1S

T1

T2

FIELD FAILURE PROTECTION - 2 UNDER CURRENT RELAY

The relay requires access to field hence limitation for its use for brushless systems.

Offset MHO relay monitors impedance at TG terminals. Without field, machine draws reactive current from system, the terminal impedance shifts from1st to 4th quadrant on the R - X plane and settles within the relay characteristic. Field failure protections are used with 1.5- 2 sec delay to ensure transient free operation.

FIELD FAILURE PROTECTION - 3 MHO TYPE RELAY

FIELD FAILURE PROTECTION - 4 MHO TYPE RELAY - 2

For large TGs, it is supplemented by under voltage relay, which overrides time delay. This ensures stability when field failure occurs say at full load & accompanied by drop in stator voltage. System is not strong enough to support VAR needs of the generator.

FIELD FAILURE PROTECTION - 5 MHO TYPE RELAY - 3

MHO relay settings are: TG with rotor angle of 90° & no leading PF operation:

Offset = 0.50 Xd’ Diameter = Xd TG

with rotor angle of upto 120° and likely leading PF operation:

Offset = 0.75 Xd’ Diameter= 0.5 Xd

OFFSET

DIA

X

R

OFFSET MHO RELAY

LOCUS

BACK UP PROTECTION

It is provided for tripping, in case system faults are not cleared. For close up faults, AVR may not be able to boost voltage and hence low fault current levels obtained. Voltage controlled over-current relays are used.The relay is designed to become more sensitive with voltage reduction and operates positively, even if fault current is less than rated.

BACK UP PROTECTION - 2

Voltage controlled over-current relays are applied for directly connected m/cs. Relay characteristic shifts from over- current to fault when input voltage falls below preset level.

The relay is time coordinated with the down stream back up protections. CURRENT

TIM

E S

ec28

2114 7

0

OVERLOAD

FAULT


For unit connected generators, single step offset MHO relay is used for back up impedance protection along with a follower timer.Relay is set to cover longest emanating line from station bus bars. Effect of in-feeds from parallel generator is also taken into account while setting the relay to the extent permitted by load.


21

51NBACK UPIMPEDANCERELAY

GEN VT

EARTHING TRANSF.

LR

GEN GEN TRANSF

STANDBY E/F RELAY

Zset = ZT + n • ZL

ZT is gen transf. leakage impedance, ZL longest line impedance, n=No of TGs.in //. Upper limit of Zset decided by max load on TG & 80% load impedance

INTERPOSING VT


Since relay is connected at TG voltage level but measures line impedance(thro’ GT impedance),input voltage from VT is phase corrected by providing Y VT to compensate phase shift due to Y GTBack up imped. relay caters for ph to ph or 3 ph faults on the line. E/F back up is provided by standby E/F relay 51N operated off neutral CT on GT side.

ANTI MOTORING PROTECTION

For steam turbine sets, motoring power is about 0.5 - 6% of rated. Lower for condensing & higher for back pressure. Gas turbines may draw 10 - 15% rated.Reverse power relay with time delay is used. While sensitive relay with about 0.5% power setting is required for STG, coarser setting of about 3% for gas turbine/engine driven sets is used.

OVER VOLTAGE PROTECTION

Over voltages may occur due to sudden load throw off and consequent turbine over-speeding. Although AVR controls voltages and speed governors control speed, back up may be required.Usually definite time over voltage relay is used. The relay should have high drop off /pick up ratio and preferably be of continuously adjustable setting.

FREQUENCY PROTECTION

Multi stage under frequency schemes are applied. Cumulative timers along with under frequency relays are used to initiate alarms, to isolate machine for a shut down if cumulative operation exceeds limits.Over frequency relays are used as a back up to mechanical over-speed protection.Under / over frequency relays are time delayed to prevent transient operation.

OVER FLUXING PROTECTION

It is used to prevent over-fluxing of GT.Over-fluxing relay measures V/f ratio - an index of over-fluxing. Typical V/f settings are: 1 - 1.3 on 110V/50Hz basis. Relays are definite time or inverse time versions with pre-trip alarm for corrective steps.Since immediate isolation of GT is not required, relay is provided with adjustable time delay thus also preventing transients

DEAD MACHINE PROTECTION

TG is protected at standstill or on barring gear, from accidental energisation.A high speed protection involving current detection in all three phases trips EHV breaker. Supplemented with under voltage relays, protection is coordinated to prevent mal-operation for close in faults.

NUMERICAL PROTECTION

Microprocessor based protection is user friendly with configurable software-based tripping matrix. It has also the following: Continuous self monitoring; facility to communicate with station control & with remote load dispatch control, reducing cabling.Events recording;flexible relay settings & reduction in CT / VT burden are possible

NUMERICAL PROTECTION - 2

It has a library of protection functions that make it easy to apply, replacing large no. of discrete relays and reduction in panelsProtection functions in numerical relays are defined by software,resulting in better algorithms for individual functions and capability to adapt to changed operating conditions.Comprehensive multi-function MP-based generator protection relay is developed.

TRIPPING MODES

Shut down or simultaneous tripping: Cl. A or interlocked / sequential trip: Class B.Class A trips ST, TG, field breaker & unit aux. transformer LV breaker together.TG differential, overall diff., stator E/F, GT UAT, restricted E/F,2nd rotor E/F, back up impedance or over-current protections initiate instant trip of whole unit on severe electrical faults.

TRIPPING MODES - 2

Class B is applied where elec. isolation of TG can be delayed. ST trips immediately. Tripping of TG,UAT, field circuit breaker is interlocked with low forward power relay. This avoids over-speeding of TG.Mode ‘Class D’ is provided for GTG which involves tripping of GCB & excitation only. GT is not tripped. It can spin at no load w/o overspeeding. Cl A trip affects GT life.

GEN PROT CKT

81C

59F2

40 59F1

81A

27

32A

32A

32A

67W

67W 67W

21

60PR60PY 60P60PB

TO RELAYS 32A,32B&67W

TO CT CKT OF AVR

TO RELAYS 40.50A,50S,21,50UT,32C&46

TO GEN INTERTURN DIEFFERENTIAL

TO GT OVERALL DIFFERENTIAL

87G

64A64B64C

CB1/9 33AZ

CT RATIO 10000/5A

PT RATIO 16.5KV/110V

R Y B

86G+ 250V DC SUPPLY -250V DC SUPPLY

FS 905LT1966

87G

64F2

87INT

64A

64BCB/9-152b 50ST

64CX

86M

86BO

86T

86R

86STA

67WT

32AT

CB1/9-33A

8AR

81/94HS300

1K

86G

FS906

DIFFERENTIAL PROT

SECOND ROTOR EARTH FAULT

INTERTURN DIFFERENTIAL

STATOR GROUND FAULT-91%

STATOR GROUND FAULT-96%

STARTUP OVERCURRENT

STARTUP GROUND FAULT

REVERSE POWER

LOW FORWARD POWER

EXCITATION PROT

UNDER FREQ. IF HL OR AVR BYPASSED

996

2BX

87GT

63GX1

63GX2

FDX1

86M

86BO

67WX

86T

86R

86STA

32BT

87UT

64AUT

196A2429

CB1/9 33AZ 59FY1

86GT

BUS BAR DIFF.-87C OR 87B,

BREAKER BACK UP PROT. 50B, 50BN

GT DIFFERENTIAL

GT BUCHOLZ RELAY

UT BUCHOLZ RELAY

LOW FORWARD / REVERSE POWER PROT

UT DIIFFERENTIAL

UT RESTRICTED EARTH FAULTTRANSFER BUS DIFFERENTIAL-87A

OVERFLUXING STAGE-2

+ 250V DC SUPPLY - 250V DC SUPPLY86GT

86M RELAY

86MLT511

30B

40GZ

46T

60AR

CB1/933AZ 59FX3

81CT

GT WDG TEMP HI 850 C

LOSS OF EXCITATION 0.5 SEC

NEGATIVE SEQ PROT

GEN FIELD CB TRIP-0.8 SEC

OVER FLUXING-1+ 30 SEC

HIGH FREQ- 51.5 + 10 SEC

+ 250V DC SUPPLY

FS 905 FS 906

- 250V DC SUPPLY

86T+

-

48V DC

48V DC

R1187

R1194

R1188

R1191

R1190R1192

86T

FS693

FS694

86T

EX.HOOD TEMP

CONDENSER VACCUM

LUB.OIL PRESSUE LOW <0.3 KG/CM2

THRUST WIER

86B RELAY

86BLT5113

51G

64BUT

+ 250V DC SUPPLY

FS 907 FS 908

- 250V DC SUPPLY

60X1 21T

94BX

64AGT

64AXT

64BXUT

GT BACK UP VER CURRENT

BACK UP IMPEDENCE

GT BACK UP EARTH FAULT

UT BACK UP PROTECTION

GT BACK UP E/F THRO AUX RELAY COTACT

UT BACK UP OVER CURRENT

UT BACK UP O/C THRO AUX RELAY CONTACT

+250VDC

86G 86GT 86B 86M 86STA 86R 86T 86BO

20COX

SV883

20COX

63QRB

PS94063QRA

PS939

TURBINE TRIP

- 250VDC

63QRA

63QRB

20COX20X

HS566 TEST

CB1/3-33AY

PS815

32CX

60Y1

20X

CB

1/3-

33A

Y

SV884

20X

20Y

20Z20

XY

Z-1

20X

YZ

-2

20X

YZ

-320Y 20Z

63QSA63QPX

63C

27E

+250VDC FDR-23

-250V DC

NRV SV

NRV SV

TURBINE TRIP

CB OPERATION-TRIPT N C

152L

152a

152TCB 9- 3T

143A

86GT

86B

86G

996

81/94

27T

98

152b

+250VDC

- 250VDC

FS903FS904

L R

CB OPERATION-CLOSE+250VDC

- 250VDC

+250VDC

- 250VDC

163A

163AX

163AX

152C

152Y

152R

152B

152CC

152CC

152CC

152L143A

152C

T N C L R

152R-b 152Y-b 152B-b

L R

FSFS

FS

FSCB-9 3C

27C

27C

CIES VALVE CONTROL+48V DC

63QRF

63QRFX

HS LOCAL/REMOTE

OPENCLOSE

20WAO20WAC

63QRG-1

63QRGX

63QRH-1

63QRHX

- 48V DC

+250V DC

FS7

FS9

FS10 FS8

- 250V DC

20WAO

20WA- 1

20WAC

96WA

20WAM

OPEN

CLOSE

20WAC

20WAO

13127

96WA

63QRGHH

72QR-4

96WA

A

20WA

R13127

FS13

63QRFX

72QR

72QRCLOSE

TRIP

FS14

CIES VALVE CONTROL

SPEEDER GEAR

R1116-1

R1123-2

R1133-1

R1124-1

R1128-1

R1127

RAISE

R1123-1

R1985-1

R1116-1OPEN AT 94%

SPEED &LESS

R1128

LOWER

R1127-1

R1124

63QSB(PS-949)

OPEN AT NO LOAD

R1134-163QSD(PS933) OPEN AT NO

LOAD

R1129

R1985

65S1 CLOSES

FOR

< 94% SPEED

- 48V DC

+ 48V DC

SPEEDER GEAR AUTO/MAN+48VDC

- 48VDC

HS816 AUTO HS816 SYNCHS816 MANUAL

18L

18R

R1133 R1134

R1132(TDPU)

1TDO 100msR1131

R1116

R1124-3

R1114

R1132R1131

CB 1/9 33AYG-1

-81

-94

A

HS HS HS

RAISERAISE RAISERAISE

LOWER LOWER LOWER

SPEEDER GEAR MOTOR

AC

RO

MA

G R

EL

AY

SER

VO

AM

P

POW

ER

PA

CK

1.5K

7575

75

R11

31

R11

27 R11

28

3 75

4-20

mA

R1127(RAISE)

R1128(LOWERR1123

R1985

R1127

R1128

FS688

FS687FS685

20COX

R1123

FS686

+ 48DC

- 48DC - 48DC

+ 48DC

GOVERNOR CIRCUIT

GEN UNLOADING+ 48VDC

- 48VDC

20COX

R1123R1124

R1120R1122R1150R1121R1117

R1122R1120

R1117

R1121R1150

R1121

R1150

STATOR FLOW vlow

STATOR FLOW vlow

STATOR FLOW vlow

STATOR COND HIGH

LP SPRAY COOLING+ 48VDC

- 48VDC

1R

----

1

TDR/1-TDO

TDR/1-TDO

1R

----(SCR)

1

SV-874

R1963

GS-939

CLOSE WHEN CV FULLY CLOSE

PS-889

63V

CLOSE COND VAC<660mm

Hs

override

Close SOP

<3.17

CLOSE ON CV FULLY OPEN

R-1963-1

W A

NRV CONTROL ED

20XYZ

LS859CLOSES ON VH LEVEL IN HPHR-6

20N1

SV 870 DE-EN TO CLOSE

4311 V-5

+ 250 V DC

- 250 V DC- 250 V DC

20N1Y 20N2Y 20N3Y 20N4Y 20N9Y

- 250 V DC

NRV CONTROL ED-CONTD

20N1Y

20N5X

SV-875

20N5

63QPX

20N5X GS 977

20N5X

20N5X

A

+ 250 V DC

20N1Y/20N5X – HPHTR

20N2Y/20N6X –LP HTR

20N3Y/2N7X

20N4Y/20N8X – RHTR( RH)

TURBINE SOLENOID RESET

- 250 V DC

+250 V DC + 48VDC

- 48VDC

20M1X

20M1X 20M2X

20M2X

20M1 20M25EX

+48V DC

CLOSE ON RAISE

CLOSE ON LOWER

33Qy 33Qy

33ay 33ay

Close for speed >106% Close for full load & above

Close at 94% speed

R 1127

R 1128

R 1131

R 1889

Differential Protection Relay – 87G

Type CAG 34 – High speed high impedance relayIt is a current relay attractive Armature – ACCurrent setting Range 0.1 to 0.4 Amps.Relay set at 0.2 Amps.Flag 87 GR, 87 GY, 87 GB (3 phases)

Inter Turn Protection Relay – 81 INT

Type – CAG 34, High speed high impedance RelayCurrent Relay Attractive Armature – ACCurrent Setting Range 0.1 to 0.4 Amps.Relay set at 0.2 Amps.Flag 87 INT R; 87 INT Y; 87 INT B (3 phases)

Stator Ground Fault Relay – 64A

Type – VDG 14 – Voltage Induction Disc type – ACAVX voltage 250V DCVoltage setting range 12.5V to 20V seal in typeRelay plug set at 12.5 volts.Time multiplier – 0.2

Stator Ground Fault Protection Relay – 64B

Type VDG 14 – Voltage operated Induction Disc type – ACVoltage setting range 12.5 to 20V seal in typeRelay plug set at 5.4 voltsTime multiplier – 0.3

Loss of Excitation Protection Relay - 40

Type – YCGF – Field Failure Relay, Off set mho type (Gen Asynchronous running detection relay)Z1 = K3 + K4

Z2 = K1 + K5

K1 = 1 (Range 0.75 to 1)K2 = 3.5 (0.5 to 4)K3 = 0.5 (0-1)

Contd.

Loss of Excitation Protection Relay – 40 Contd.

K4 = 3 (0.5 – 3)K5 = 25.9 (6.95 to 50)Off set = Z1 = K2 = K3+K4 = 3.5Circle = Z2 = K1 x K5 = 25.9

Operates through timer VAT {Definite time delay type} 40 (2B) – 2 sec. Range [2-10 Sec.]

Contd.

Loss of Excitation Protection Relay – 40 Contd.

Under Voltage Protection for Field Failure-27Instantaneous under voltage relay type VAGM 22Attractive Armature Voltage RelayAC U/V or O/V relay with variable settings and high drop off / of pick up ratioRange 44 – 88 volts; set at 73.2 volts

Unbalance current protection relay – 46, 46A

(Negative Sequence Current Protection)Type CTN – Negative sequence relay with inverse time characteristicStatic RelayI2S K3

7.5 110 1.78 Plug set at 7.5%

Contd.

Unbalance current protection relay – 46, 46A Contd.

15 420 7.130 16 [I2/In]2t=K1K3;In

=5 amps

Negative Sequence O/C Alarm Relay – 46A

Range 70% -100% of tripSet at 70% (70% of 7.5)Timer 5 Sec. (fixed)

Low Forward Power Relay – 32A / 32B

Type WCD 11 – High speed polyphase sensitive power relayFixed setting relay type; Sensitivity <0.5%Low forward power relay operates through a timer relay VAT 11Definite time delay relay Type 32 AT – 2.5 Sec., 32 BT – 6.5 seconds

Reverse Power Protection Relay – 67W

Type WCD 11 Polyphase reverse power relayFixed setting relay, sensitivity < 0.5%Operates through a timer VAT 11 (Range 0.5 – 3 sec.)67 Wt set at 2.5 sec.

Under Frequency / Over frequency Relays(Combined Unit Static Relays)

Type FCX 103 b of Hindustan Brown Boveri81A / 81 AT81B / 81 BT81C / 81 CT81 / 94 – Timer81 A – Under frequency at 47.77 Hz

Contd.

Under Frequency / Over frequency Relays(Combined Unit Static Relays) Contd.

81 B – Under frequency at 47.5 Hz81 C – Over frequency at 51.5 Hz81 AT set at 3 Sec; 81 BT set at 0.5 sec = Range 0.1 to 99.9 sec.81 CT set at 10 Sec. = Range 6 to 60 sec.81/94 T set at 1 sec; Time delay relay type VTT – Static timer (0.1 to 99.9 sec.)

Backup Protection Relay - 21

Type ZAUM 71 – Definite time Impedance RelayGenerator Under Impedance Protection relayFlags 21 R, 21 Y, 21B; 21 Rx, 21 Yz, 21BxTiming set at 2 seconds (Range 2-10 sec.)

Contd.

Backup Protection Relay – 21Contd.

Impedance Setting = 17.3 x ZZ = K1 + K2

K1 = 0 K2 = 0K1 = 0

K2 = 4 K2 = 4K2 = 4

BZ AZ CZZ = 1,732 x 4 = 6.928

Start up E/F Protection Relay – 64C

Instantaneous over voltage relayType DBA 4 (of AEI-UK) – Moving coil relay with variable settings and a single adjustable setting.Relay operates on rectified DC voltage.Range 5 – 20 voltsRelay set at 7.5 volts

Start up over current protection relay – 50S

Type CAU-39 Definite time O/C relay(range 20-80% of 5A) operates on rectifiedDC

current Plug set at 1 AmpsTiming range 0.05 to 3 sec; Set at 0.5 sec.

Rotor Earth Fault Protection Relay – 64F

Type –VME21 – Rotor E/F relay (field ground)Flag – 64 Fx; Relay uses a sensitive balanced armature polarised element.Fixed setting relay – operates at 1.8MA.

2nd Rotor E/F Protection Relay

Type – CAEM 33Fixed setting 1 mA.

Generator Field O/C Protection Relay – 1.0C R

Type – DBB 4; moving coil relay variable settings to adjustable settings.Set at 1.75 IFR (4000 A) Operates through the Timer 3TR

Generator Field O/V Protection Relay – 1.0V R

Type – VAGMSetting steps : 121, 126.5, 132, 137.5, 143, 148.5, 154 voltsSet at 143 volts (normal 110 volts); operates through the timer 3 TR.L43 corresponds to 520 volts (excitation voltage).

BEST WISHES

TO UU ALL

63QRA (PS 939) ) Relay oil pressure after main trip valve. `NO’

63QRB (PS 940) ) contact closes for pr > 3.52 Kg/cm2 .

So 20COX is energised and 20COX `NO’ contact is in closed condition.

Whenever a protection relay (86G, 86GT, 86B, 86M, 86STA, 86R, 86T, 86BO) acts, SV-883 pick up and trip signal is initiated.

Turbine Trip

PS-815: Pressure switch in Bled steam to deaerator line set to Close at 1.0 Kg/cm2 rising pressure, opens at 0.9 Kg/cm2.

32 CX : `NC’ contact closes when the generator power output is more than 80 MW (30%).

60 Y1 : `NC’ contact closes when voltage is normal.

20X : relay pick up either on CB-1/9 open (33AY) or on dropping of wattmetric relay, provided 4th Extraction pressure > 0.9 Kg/cm2. Then OLG SV-884 energises and …..

Turbine Trip

Turbine Trip

63C : Differential pressure between Condenser and Deaerator `NO’ contact closes when /\ P > 0.21 Kg/cm2.

Normally 20X, 20Y & 20Z relays are de-energised and So 20 XYZ-1,-2 , -3 are picked up condition whenever turbine trip signal goes, 20X/20Y,20Z relay energise, drop out 20XYZ relays and all reheater valves closes on turbine trip.

143A : Selector Switch for Local or Remote

152L : Selector Switch for Trip, Normal or Close.

152a : When CB is in closed condition, this contact close.

152T : CB Trip Coil

152b : When CB is in open condition, this contact closes.

98 : Supervision relay to check healthiness of trip coil circuit when the CB is in open condition.

CB93T: When the CB is selected to Remote, Circuit breaker can be tripped only through 3T relay.

Any protections acts, directly 152T pick up through the Lock out relay and tripping will be initiated.

27T : Under voltage relay to supervise supply healthiness.

CB TRIP

152C : CB closing coil

152CC : Once 152C pick up and the contact closes, 152CC of each phase energises and CB closes.

163AX: If pole discrepancy do not exist, 163AX contact closes and permits 152C Coil to pick up whenever closing signal initiated through Local or 3C/relay.

27C : Under voltage relay to supervise the closing coil circuit supply healthiness when the CB is in open condition.

CB CLOSE

20 WAO : Opening relay for manual opening of CIES Valves from Local/Remote.

20 WAC : Closing relay for manual closing of CIES Valve from Local/Remote.

63QRH#1 : Relay oil pressure switch contact RH CIES Valve trip Cylinder – Closes below 8.43 Kg/cm2 .

63 QRG#1: Relay Oil pressure Switch CIES Valve trip Cylinder – closes below 8.43 Kg/cm2.

63 QRHX: Auxiliary relay for PS 63 QRH

CIES VALVE

63 QRGX: Auxiliary relay for PS 63 QHG

63 QRF : Relay Oil Pressure Switch after main trip Valve – Contact set for 3.52 Kg/cm2.

63 QRFX : Auxiliary relay for PS 63 QRF.

Whenever closing or opening operations is done, 20 WAC or 20 WAO picks up.

Whenever turbine trip cylinder relay oil pressure falls below 8.43 kg/cm2, 63QRGX and 63QRHX pick up. Normally relay oil pressure after main trip valveis higher than 3.53 kg/cm2, 63QRF contact is in close condition and so 63QRFX is energised.

CIES VALVE

20WAO : Opening relay contact20WAC : Closing relay contact96WA : Aux. Relay contact for LH CIES valve reset20WA-1} : Limit switch contact open when the LHCIES 20WA-2} valve is fully opened/closedR13127 : Permissive relay for closing of CIES valve to

the limit switch63QRGX-2 : LH CIES valve trip cylinder relay oil

pressure switch aux. Contact closes below 8.43 kg/cm2

72QR : Aux. Relay for 63QRF(latched)63QRFX : Relay oil pressure switch after the main trip

valve contact set for 3.52 kg/cm2 in trip condition

CIES VALVE

While TG is running, whenever opening command is initiated through 20WAO ‘NO’ contact by closing and 20WAM operate in open direction. Similarly CIES valve can be closed closing of 20WAC ‘NO’ contact, since 13127 is also closed as long as 20WA-2(LS not acted) is in closed condition and 13127 relay is picked up.

During turbine trip, CIES valve trip cylinder pressure falls below 8.43 kg/cm2 63QRGX-2 closes and 96WA energises and then give closing signal directly to CIES valve closing coil

CIES VALVE

65S1 : Limit switch on speeder gear, the contact close for speed less than 94%

R1128 :Aux. Relay for generator run down-manualR1985 : The relay energises on 65S1 contact closes,

open out ‘NC’ contact and prevent generator unloading

R1123 : Normally this relay is energised through 20COX’NO’ contact closed and so ‘NC’

contact in R1128 is open. Whenever turbine trips 20COX contact open, this relay de- energise and initiate generator unloading

SPEEDER GEAR

SPEEDER GEAR

63QSD/ 63QSB} : Sensitive oil pressure switch (interceptor).Normal operation the contacts are closed and ‘NO’ contact of R1124 is in open condition. Whenever generator unloading is called from stator water flow very low or conductivity high,”NO’ contact of R1124 closes and R1128 pick up and unload generator.

SPEEDER GEARR1116 : Aux. Relay- low vaccum unloadingR1134 : Interposing relay for speeder gear

lowering through HS in manual or synchro mode

R1127 : Aux. Relay for speeder gear power raise-manual

This relay can pick up and raise generator load through R1133 from manual/synchro. Power raise, provided turbine is not tripped and generator unloading is not existing

SPEEDER GEARHS816 : Hand switch has three positions-

manual,synchro and autoR1133 : Aux. Relay for speeder gear raiseR1134 : Aux. Relay for speeder gear lowR1131 : Aux. Relay for auto pressure raise or

lower. This relay pick up on satisfying the following conditions

A:Under frequency does not existB:Breaker CB 1/9 closeC:Condenser vacuum is normal(R1114) so that dump valve is

not closed.D:Generator unloading does not existE:Condenser low vacuum unloading does not exist18R/18L :Raise/Lower contacts through HS auto synchro

mode

R1131 : Aux. Relay contact- closed during auto pressure control for

speeder gear.R1127/1128: Aux. Relay for manual raise or lower ‘NO’

contact closes on manual action and ‘NC’ contact open for cutting BPC signal

R1889 : In manual mode, whenever raise or lower PB is pressed, it de-energise R1889. ‘NO’ contact is wired across the input terminals of servo amplifier and ‘NC’ contact is wired in the output circuit

Gen-unloading

R1120 : Generator unloading will be initiated by energising this relay on two out of three logic relays(1117,1121,1150) by stator water flow very low

R1122 : Generator unloading will be initiated through stator water conductivity very high

R1124 : Timer relay for generator unloading

Documents

Generator Protection