Generator Protection

MADRAS ATOMIC POWER STATION

TURBO GENERATOR PROTECTION Presented by

J.ROOBY

March 2001

ELECTRICAL PROTECTIONS TRIP TYPE:: DIFFRENTIAL STATOR EARTH ROTOR EARTH OVERVOLTAGE OVERCURRENT UNBALANCE UNDERFREQUENCY

TT

GCB

FB

PROTECTIONS - 2 TRIP TYPE UNDEREXCITATION W/O LOSS OF FIELD WITH LOSS OF FIELD REVERSE POWER LONG TIME

SHORT TIME (OPERATES ONLY AT TT)

TT

GCB

FB

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 tripped Over-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

Generator differential Stator earth fault Rotor earth fault - 1st

- 2nd Over-voltage Overload Negative ph seq current Inter-turn for stator wdg. Reverse power Loss of field

TT

GCB

FB A

THW: MECHANICAL PROTECTIONS Bearing babbit babbit Oil out Oil out H2 seal-oil inlet outlet DM Conductivity: DM inlet temp.

75° High 80° HH 60° High 65° HH 45°High 70°High 20µMho: <39°: 44°: >48°:

Oil temp.,flow Trip B manual Oil temp.,flow Trip B manual Flow,cooler,CW Trip B manual Trip B Auto Reduce CW flow Cooler; Unload 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,Cooler Wdg. temp. 75° Unload to normalize Diff in 2 RTDs >20° Run down,man.trip B Cold H2 High 44°C HighHigh 55°

W inlet temp,press,& Unload.Trip B manual

H2 hot gas High75° Core temp High95°

CW press,temp,flow

Unload,Trip B manu

MECHANICAL PROTECTIONS - 3 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

MECHANICAL PROTECTIONS - 4

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. Time

DEFINITE MINIMUM TIME

Current

OVER-CURRENT RELAY INDUCTION TYPE

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. TRIP Time of travel and over -current settings can be altered. CURRENT

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

STATOR EARTH FAULT - 3 IDMT TYPE RELAY 64S STATOR WINDING

64S

SOLID EARTHING

LOW RATIO CT

64S

RESISTANCE EARTHING

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

DISTBN. TRANSF.

LOAD RESISTANCE

LR 64S 64S

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

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.

STATOR GROUND FAULTS - 3

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

STATOR GROUND FAULTS - 4 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.

STATOR GROUND FAULTS - 5 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

BLIND ZONE N Rn

V3

N VL3

VN3 V3

VN3

L

F

L V3

VN3F BLIND ZONE

VL3 VL3 VN3 VL3 VN3 N L 0 0.2 0.6 1.0 FAULT POSITION

VL3F VL3Q

VN3Q Q: HEALTHY F: FAULTY

STATOR GROUND FAULTS - 8 SAMPTH & PRATAPKUMAR, ENGLISHELECTRIC

PVMM RELAY INPUTS G NEUTRAL DISPLACEMENT DETECTOR UNIT 3rd HARMONIC VOLTAGE COMPARATOR GROUND TRANSFORMER

LINE PT

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.

GENERATOR DIFFERENTIAL - 3 STATOR WDG.

RESISTORS 87

87

87

HIGH IMPEDANCE RELAY

GENERATOR DIFFERENTIAL - 4 STATOR WDG.

R Y B N

64 64 ADDL. CT IF EARTHING TAP OFF IS BEFORE THE NEUTRAL CT

GENERATOR DIFFERENTIAL - 5 CT A (n/1)

CT B (n/1) T

87

If RL Lead Resistance RCT CT B SATUR.

CT A IS RST ACTIVE VS 87 If/n • 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.

GENERATOR DIFFERENTIAL - 6

Associated 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}

GENERATOR DIFFERENTIAL - 7 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.

 ET

UAT 

CT  Y

GT Y

Y Y



Y

87

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%

UNBALANCED LOADING NEGATIVE SEQUENCE RELAY ‘46’ R

Y B ZB

IB

IR VR + VB = 0 VR IB

VB

IY

ZR

IR

46

IR VR

VR + VB VB

IB IY

ROTOR EARTH FAULT First 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 + Ex AUX AC SUPPLY

FIELD WINDING

RELAY

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

POTENTIOMETER

+

2nd 1st

Ex

AUX AC SUPPLY

64R1

+

TRIP

64R2

mA

1st E/F Balance Test 2nd E/F

1st ROTOR EARTH FAULT POTENTIOMETER

+ Ex

E/F AUX AC SUPPLY

64R1

•Bridge gets unbalanced. •Relay 64 R1 gets signal. •Alarm is initiated. ACA - PROT - 48 / 80

1st E/F

BALANCE POSITION POTENTIOMETER

+ Ex

1st E/F AUX AC SUPPLY

64R1

+

mA HAS NO CURRENT

mA

1st E/F Balance Test 2nd E/F

TESTING FOR BALANCE POTENTIOMETER

+ Ex

1st

AUX AC SUPPLY

64R1

+

TRIP

64R2

mA

1st E/F Balance Test

2ND ROTOR EARTH FAULT POTENTIOMETER

+

2nd

Ex 1st

+

RELAY 64 R2 GETS OUT OF BALANCE CURRENT & INITIATES TRIPPING 1st E/F Balance Test

2nd E/F TRIP

64R2

mA

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.

FIELD FAILURE PROTECTION - 2 UNDER CURRENT RELAY FCB FIELD WINDG.

EXCITATION

E D.R.

50 T1

T2

ALARM / TRIP

50:FIELD UNDER CURR RELAY T1 OFF DELAY TIMER 0.1-1S T2 ON DELAY TIMER 0.1-1S

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

FIELD FAILURE PROTECTION - 3 MHO TYPE RELAY

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 - 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

X LOCUS R

MHO relay settings are: TG with rotor angle of 90° & OFFSET no leading PF operation: Offset = 0.50 Xd’ DIA Diameter = Xd TG with rotor angle of upto 120° and OFFSET MHO likely leading PF operation: RELAY Offset = 0.75 Xd’ Diameter= 0.5 Xd

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 falls28below preset level. The relay is time coordinated with the down stream back up protections.

21 14 7 0

OVERLOAD FAULT CURRENT

BACK UP PROTECTION - 3 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.

BACK UP PROTECTION - 4 GEN

 LR EARTHING TRANSF.

GEN TRANSF 

BACK UP 21 IMPEDANCE RELAY

51N STANDBY E/F RELAY

GEN VT 

INTER POSING VT

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

BACK UP PROTECTION - 5 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 GT Back 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 overfluxing. 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 panels Protection 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 60PR R

Y

60PB 60P

B

59F2

PT RATIO 16.5KV/110V 81C

CT RATIO 10000/5A

60PY

40

32A

81A

59F1

27

32A

TO RELAYS 32A,32B&67W TO CT CKT OF AVR

87G TO RELAYS 40.50A,50S,21,50UT,32C&46 TO GEN INTERTURN DIEFFERENTIAL TO GT OVERALL DIFFERENTIAL CB1/9 33AZ

64C

64B

64A

32A

67W

67W

67W

21

86G

+ 250V DC SUPPLY LT1966

FS 905

-250V DC SUPPLY FS906 86G

87G DIFFERENTIAL PROT 64F2 SECOND ROTOR EARTH FAULT 87INT

INTERTURN DIFFERENTIAL

64A

STATOR GROUND FAULT-91%

64B CB/9-152b

50ST 64CX

STATOR GROUND FAULT-96% STARTUP OVERCURRENT STARTUP GROUND FAULT

86M

67WT 32AT

86BO

86T

REVERSE POWER LOW FORWARD POWER

CB1/9-33A

86R 86STA 81/94

8AR

EXCITATION PROT

HS300

1K

UNDER FREQ. IF HL OR AVR BYPASSED

86GT

- 250V DC SUPPLY

+ 250V DC SUPPLY 996 2BX 87GT

63GX1 63GX2 FDX1 86M

32BT

67WX

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

86BO 86T 86R 86STA

87UT

UT DIIFFERENTIAL

64AUT 2429 CB1/9 33AZ

196A 59FY1

UT RESTRICTED EARTH FAULT TRANSFER BUS DIFFERENTIAL-87A OVERFLUXING STAGE-2

86M RELAY + 250V DC SUPPLY

LT511

- 250V DC SUPPLY

86M

FS 906

FS 905

30B GT WDG TEMP HI 850 C

40GZ LOSS OF EXCITATION 0.5 SEC

46T NEGATIVE SEQ PROT

60AR CB1/933AZ

GEN FIELD CB TRIP-0.8 SEC

59FX3

81CT

OVER FLUXING-1+ 30 SEC

HIGH FREQ- 51.5 + 10 SEC

86T 48V DC

+

FS693

EX.HOOD TEMP

R1187

R1188 R1190

R1194

R1191

CONDENSER VACCUM 86T

86T 48V DC -

FS694

R1192

LUB.OIL PRESSUE LOW <0.3 KG/CM2

THRUST WIER

86B RELAY + 250V DC SUPPLY

LT5113

- 250V DC SUPPLY

86B

FS 908

FS 907

51G GT BACK UP VER CURRENT 60X1

21T

BACK UP IMPEDENCE 94BX 64AGT

UT BACK UP PROTECTION GT BACK UP EARTH FAULT

64AXT GT BACK UP E/F THRO AUX RELAY COTACT

64BUT UT BACK UP OVER CURRENT 64BXUT UT BACK UP O/C THRO AUX RELAY CONTACT

TURBINE TRIP

+250VDC

86G

86GT 86B

86M

86STA 86R

86T

86BO

63QRA

63QRB

PS939

PS940

20COX 20COX SV883

- 250VDC

TURBINE TRIP

+250VDC FDR-23

NRV SV

63QRB 20X

63C

20Y PS815 20Z

27E

HS566 TEST

20X

63QPX

63QSA

63QRA

CB1/3-33AY 32CX

20Y

20Z

20XYZ-3

60Y1 SV884 20X

NRV SV -250V DC

20COX

CB OPERATION-TRIP - 250VDC +250VDC

152L T N C

L R 152a

FS903

FS904 152T

CB 9- 3T

143A

86GT 86B 81/9 4 86G

996

27T 152b 98

CB OPERATION-CLOSE - 250VDC +250VDC FS

163A FS

163AX

152R 152C

152CC

152Y 152CC 152B 152CC 152L T N C

+250VDC FS

143A L R

163AX

- 250VDC

L R 152C

CB-9 3C

27C 27C

152R-b

152Y-b

152B-b

FS

CIES VALVE CONTROL +48V DC

HS LOCAL/REMOTE 63QRG-1

63QRF CLOSE

OPEN

63QRFX

63QRH-1

20WAC

20WAO

- 48V DC

63QRGX

63QRHX

+250V DC

CIES VALVE CONTROL FS7

FS9

FS13 20WAO 63QRGHH 20WAC 20WAC

63QRFX

20WA 96WA

96WA

72QR-4

20WAO

72QR

13127 96WA

R13127 CLOSE

72QR TRIP

20WA- 1 A

CLOSE OPEN

FS14

20WAM

- 250V DC FS10

FS8

SPEEDER GEAR

+ 48V DC

R1123-1 R1116-1 R1124-1

R1124

R1985-1 OPEN AT 94% SPEED &LESS

R1116-1

63QSB(PS-949) OPEN AT NO LOAD

R1134-1

63QSD(PS933) OPEN AT NO LOAD

65S1 CLOSES FOR

R1123-2

R1127-1

< 94% SPEED

R1133-1 R1128-1 R1128 LOWER

R1985

R1127

R1129

RAISE

- 48V DC

SPEEDER GEAR AUTO/MAN +48VD C HS816 AUTO

HS816 SYNC

HS816 MANUAL

CB 1/9 33AY R1131

18L

HS

R1132 RAISE R1114

HS LOWER RAISE

HS

LOWER RAISE

18R LOWER

R11243 R1116 R1131

R1132(TDPU) 1TDO 100ms

48VDC

R1133

R1134

ACROMAG RELAY

R1128

R1127

R1131 4-20mA + 48DC

1.5K 75

+ 48DC

FS685

FS687

R1985

75

20COX

POWER PACK

R1128(LOWER R1123

SPEEDER GEAR MOTOR

75

R1127 R1127(RAISE)

R1123 R1128

FS686

- 48DC

FS688

- 48DC

GOVERNOR CIRCUIT

GEN UNLOADING + 48VDC

20COX

STATOR COND HIGH STATOR FLOW vlow

STATOR STATOR FLOW vlow FLOW vlow

R1117

R1120 R1121

R1117

R1121

R1150

R1121

R1122

- 48VDC

R1150

R1120

R1122

R1150

R1124

R1123

LP SPRAY COOLING + 48VDC

PS-889

GS-939 CLOSE WHEN CV FULLY CLOSE

1R

Close SOP

63V

----

<3.17

CLOSE COND VAC<660mm

1

Hs

TDR/1-TDO

override

SV-874

1R TDR/1-TDO

----(SCR) 1

- 48VDC

A

W

R1963

CLOSE ON CV FULLY OPEN

R-1963-1

NRV CONTROL ED + 250 V DC

20XYZ

LS859 CLOSES ON VH LEVEL IN HPHR-6 20N1Y

20N2Y

20N3Y

20N1 SV 870 DEEN TO CLOSE 4311 V-5 - 250 V DC - 250 V DC

20N4Y

20N9Y

NRV CONTROL ED-CONTD + 250 V DC 20N1Y/20N5X – HPHTR 20N1Y

20N2Y/20N6X –LP HTR

63QPX

20N3Y/2N7X 20N4Y/20N8X – RHTR( RH)

20N5X 20N5X

GS 977

20N5X

20N5X

A

SV-875 20N5

- 250 V DC

TURBINE SOLENOID RESET + 48VDC

+250 V DC

20M1X

20M2X

20M1X 20M1

20M2X

20M2

- 48VDC - 250 V DC

5EX

+48V DC

R 1889

CLOSE ON LOWER

CLOSE ON RAISE

R 1127

33ay

33Qy Close for speed >106%

33Qy Close for full load & above

Close at 94% speed

33ay

R 1128

R 1131

Differential Protection Relay – 87G Type CAG 34 – High speed high impedance relay It is a current relay attractive Armature – AC Current 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 Relay Current Relay Attractive Armature – AC Current 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 – AC AVX voltage 250V DC Voltage setting range 12.5V to 20V seal in type Relay plug set at 12.5 volts. Time multiplier – 0.2

Stator Ground Fault Protection Relay – 64B Type VDG 14 – Voltage operated Induction Disc type – AC Voltage setting range 12.5 to 20V seal in type Relay plug set at 5.4 volts Time 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 K5 Off set Circle =

= = = Z2

3 (0.5 – 3) 25.9 (6.95 to 50) Z1 = K2 = K3+K4 = 3.5 = 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-27 Instantaneous under voltage relay type VAGM 22 Attractive Armature Voltage Relay AC U/V or O/V relay with variable settings and high drop off / of pick up ratio Range 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 characteristic Static Relay I2S K3 7.5 1 10 1.78 Plug set at 7.5% Contd.

Unbalance current protection relay – 46, 46A Contd. 15 20 30

4 7.1 16

[I2/In]2t

=K1K3;In =5 amps

Negative Sequence O/C Alarm Relay – 46A Range 70% -100% of trip Set at 70% (70% of 7.5) Timer 5 Sec. (fixed)

Low Forward Power Relay – 32A / 32B Type WCD 11 – High speed polyphase sensitive power relay Fixed setting relay type; Sensitivity <0.5% Low forward power relay operates through a timer relay VAT 11 Definite 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 relay Fixed 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 Boveri 81A / 81 AT 81B / 81 BT 81C / 81 CT 81 / 94 – Timer 81 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 Hz 81 C – Over frequency at 51.5 Hz 81 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 Relay Generator Under Impedance Protection relay Flags 21 R, 21 Y, 21B; 21 Rx, 21 Yz, 21Bx Timing set at 2 seconds (Range 2-10 sec.) Contd.

Backup Protection Relay – 21 Contd.

Impedance Setting = 17.3 x ZW Z = K1 + K2 K1 = 0 K2 = 0K1 = 0 K2 = 4 K2 = 4K2 = 4 BZ AZ CZ Z = 1,732 x 4 = 6.928W

Start up E/F Protection Relay – 64C Instantaneous over voltage relay Type 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 volts Relay 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 Amps Timing 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 33 Fixed 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 – VAGM Setting steps : 121, 126.5, 132, 137.5, 143, 148.5, 154 volts Set at 143 volts (normal 110 volts); operates through the timer 3 TR. L43 corresponds to 520 volts (excitation voltage).

BEST WISHES TO U ALL

Turbine Trip

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 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.

CB 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 CLOSE

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.

CIES VALVE 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 20WAC 96WA 20WA-1} 20WA-2} R13127

: Opening relay contact : Closing relay contact : Aux. Relay contact for LH CIES valve reset : Limit switch contact open when the LHCIES valve is fully opened/closed : Permissive relay for closing of CIES valve to the limit switch 63QRGX-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

SPEEDER GEAR 65S1 R1128 R1985 R1123

: Limit switch on speeder gear, the contact close for speed less than 94% :Aux. Relay for generator run down-manual : The relay energises on 65S1 contact closes, open out ‘NC’ contact and prevent generator unloading : 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 deenergise and initiate generator unloading

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 GEAR R1116 R1134

: Aux. Relay- low vaccum unloading : 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 GEAR HS816 : Hand switch has three positions-

manual,synchro and auto R1133 : Aux. Relay for speeder gear raise R1134 : Aux. Relay for speeder gear low R1131 : Aux. Relay for auto pressure raise or lower. This relay pick up on satisfying the following conditions A:Under frequency does not exist B:Breaker CB 1/9 close C:Condenser vacuum is normal(R1114) so that dump valve is not closed. D:Generator unloading does not exist E:Condenser low vacuum unloading does not exist 18R/18L :Raise/Lower contacts through HS auto

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