generator protections basics
DESCRIPTION
protection Relaynumerical relaysTRANSCRIPT
GENERATOR PROTECTIONGENERATOR PROTECTION
TYPES OF PROTECTIONTYPES OF PROTECTION TYPE OF PRIME - MOVER AND CONSTRUCTION
MW AND VOLTAGE RATINGS
TYPE OF PRIME - MOVER AND CONSTRUCTION
MW AND VOLTAGE RATINGS MW AND VOLTAGE RATINGS
MODE OF OPERATION
MW AND VOLTAGE RATINGS
MODE OF OPERATION MODE OF OPERATION
METHOD OF CONNECTION TO POWER SYSTEMS
MODE OF OPERATION
METHOD OF CONNECTION TO POWER SYSTEMS
METHOD OF EARTHING METHOD OF EARTHING
GENERATOR PROTECTIONGENERATOR PROTECTION
PRIME MOVERSPRIME MOVERSPRIME MOVERSPRIME MOVERS
STEAM TURBINESSTEAM TURBINESSTEAM TURBINES
GAS TURBINES
STEAM TURBINES
GAS TURBINES
HYDROHYDRO
DIESELDIESEL
GENERATOR PROTECTIONGENERATOR PROTECTION
CONSTRUCTIONCONSTRUCTION
CYLINDRICAL ROTORCYLINDRICAL ROTOR
CONSTRUCTIONCONSTRUCTION
CYLINDRICAL ROTOR
SALIENT POLE
CYLINDRICAL ROTOR
SALIENT POLE
MODE OF OPERATIONMODE OF OPERATION
BASE LOAD
PEAK LOAD
BASE LOAD
PEAK LOADPEAK LOAD
STAND - BY
PEAK LOAD
STAND - BY
GENERATOR PROTECTIONGENERATOR PROTECTION
CONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEM
DIRECTDIRECT
~
GENERATOR PROTECTIONGENERATOR PROTECTION
CONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEMCONNECTION TO POWER SYSTEM
DIRECTDIRECT
~
VIA TRANSFORMERVIA TRANSFORMERVIA TRANSFORMERVIA TRANSFORMER
~~
GENERATOR PROTECTIONGENERATOR PROTECTION
METHOD OF EARTHINGMETHOD OF EARTHINGSOLIDSOLID
GENERATOR PROTECTIONGENERATOR PROTECTION
METHOD OF EARTHINGMETHOD OF EARTHINGSOLIDSOLID
RESISTANCERESISTANCE RRESISTANCERESISTANCE R
GENERATOR PROTECTIONGENERATOR PROTECTION
METHOD OF EARTHINGMETHOD OF EARTHINGSOLIDSOLID
RESISTANCERESISTANCE RRESISTANCERESISTANCE R
HIGH IMPEDANCEHIGH IMPEDANCE R
GENERATOR PROTECTIONGENERATOR PROTECTION
REQUIREMENTSREQUIREMENTS DETECT FAULTS ON THE GENERATOR DETECT FAULTS ON THE GENERATOR
PROTECT FROM ABNORMAL OPERATING CONDITIONS
SO G O O C S S
PROTECT FROM ABNORMAL OPERATING CONDITIONS
SO G O O C S S ISOLATE GENERATOR FROM UNCLEARED SYSTEM FAULTS
ISOLATE GENERATOR FROM UNCLEARED SYSTEM FAULTS
ACTIONS REQUIREDURGENT
ACTIONS REQUIREDURGENT NOT URGENT ALARM NOT URGENT ALARM
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTION
PROVIDES HIGH SPEED PROTECTION FOR ALL FAULT PROVIDES HIGH SPEED PROTECTION FOR ALL FAULT PROVIDES HIGH SPEED PROTECTION FOR ALL FAULT TYPES
PROVIDES HIGH SPEED PROTECTION FOR ALL FAULT TYPES
MAY BE HIGH IMPEDANCE TYPE
OR
MAY BE HIGH IMPEDANCE TYPE
OR
BIASED DIFFERENTIAL TYPEBIASED DIFFERENTIAL TYPE
GOOD QUALITY CT’S ARE REQUIRED AT LINE AND NEUTRAL ENDS
GOOD QUALITY CT’S ARE REQUIRED AT LINE AND NEUTRAL ENDS
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTION
HIGH IMPEDANCE TYPE HIGH IMPEDANCE TYPE
~Differential Relay
Stabilising Resistor
ZG9323
g
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONHIGH IMPEDANCE TYPEHIGH IMPEDANCE TYPE
~RCT
If RCT
2RV
2RL
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONHIGH IMPEDANCE TYPEHIGH IMPEDANCE TYPE V = IV = Iff x { Rx { RCTCT + 2R+ 2RL L }}
Z = V / IZ = V / IS S
~RRSTAB STAB = Z = Z -- RRRELAYRELAY
RCTIf RCT
2RL
V2RL
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONHIGH IMPEDANCE TYPEHIGH IMPEDANCE TYPE
STABILISING RESISTOR CALCULATION
Rstab = If x ( RCT + 2 RL) ( VA )
STABILISING RESISTOR CALCULATION
Rstab = If x ( RCT + 2 RL) ( VA )Rstab If x ( RCT 2 RL) ( VA )Is Is2
WHERE
Rstab If x ( RCT 2 RL) ( VA )Is Is2
WHEREWHEREIf = MAXIMUM THROUGH FAULT CURRENTRCT = RESISTANCE OF CT WINDING2R TWO WAY LEAD RESISTANCE
WHEREIf = MAXIMUM THROUGH FAULT CURRENTRCT = RESISTANCE OF CT WINDING2R TWO WAY LEAD RESISTANCE2RL = TWO WAY LEAD RESISTANCEVA = RELAY BURDENIs = RELAY SETTING
2RL = TWO WAY LEAD RESISTANCEVA = RELAY BURDENIs = RELAY SETTING
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONHIGH IMPEDANCE TYPEHIGH IMPEDANCE TYPE
EXAMPLE
50 MVA 11KV F L C = 2624 Amps
EXAMPLE
50 MVA 11KV F L C = 2624 Amps50 MVA 11KV F. L. C. = 2624 Amps
Xd’’ = 18 % C. T. RATIO = 3000 / 1
50 MVA 11KV F. L. C. = 2624 Amps
Xd’’ = 18 % C. T. RATIO = 3000 / 1
RCT = 3 Ohms 2RL = 2 OhmsRCT = 3 Ohms 2RL = 2 Ohms
SETTING = 0.5ASETTING = 0.5A
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONHIGH IMPEDANCE TYPEHIGH IMPEDANCE TYPEFAULT CURRENT ( I ) 50 103 14579 AFAULT CURRENT ( I ) 50 103 14579 AFAULT CURRENT ( IF ) = 50 x 103 = 14579 A
1.732 x 11 x 0.18FAULT CURRENT ( IF ) = 50 x 103 = 14579 A
1.732 x 11 x 0.18
RSTAB = IF x ( RCT + 2 RL ) ( VA )RSTAB = IF x ( RCT + 2 RL ) ( VA )
= 4.86 A ( Sec )= 4.86 A ( Sec )
Is Is2
= 4.86 x (3 + 2 ) 1 Is Is2
= 4.86 x (3 + 2 ) 1
0.5 0.52
= 48.6 - 4 = 44.6 Ohms0.5 0.52
= 48.6 - 4 = 44.6 Ohms
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTION
HIGH IMPEDANCE TYPEHIGH IMPEDANCE TYPE
CT REQUIREMENTCT REQUIREMENT
ACCURACY CLASS : PS CLASSACCURACY CLASS : PS CLASS
KNEE POINT VOLTAGE VK > 2 IF ( RCT + 2RL )
MAGNETISING CURRENT I < 3 % OF In AT V / 2
KNEE POINT VOLTAGE VK > 2 IF ( RCT + 2RL )
MAGNETISING CURRENT I < 3 % OF In AT V / 2MAGNETISING CURRENT IMAG < 3 % OF In AT VK / 2 MAGNETISING CURRENT IMAG < 3 % OF In AT VK / 2
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONLOW IMPEDANCE TYPELOW IMPEDANCE TYPE
~
BIAS COIL
BIAS COILOPERATING COILZG9323
BIAS COIL
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTION
LOW IMPEDANCE TYPELOW IMPEDANCE TYPE
OPERATEOPERATENT
NT
OPERATEOPERATE
UR
REN
UR
REN
RESTRAINRESTRAIN
DIF
F. C
DIF
F. C
BIAS CURRENT BIAS CURRENT
DD
GENERATOR PROTECTIONGENERATOR PROTECTION
DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONOVERALL DIFFERENTIAL PROTECTION SCHEMEOVERALL DIFFERENTIAL PROTECTION SCHEME
~ G TG T
UAT
ICTRELAY
GENERATOR PROTECTIONGENERATOR PROTECTION
OVERALL DIFFERENTIAL PROTECTIONOVERALL DIFFERENTIAL PROTECTION BIASED RELAYS SHOULD ONLY BE USED BIASED RELAYS SHOULD ONLY BE USED
NO MAG - INRUSH AS TRANSFORMER VOLTAGE IS GRADUALLY DEVELOPED
NO MAG - INRUSH AS TRANSFORMER VOLTAGE IS GRADUALLY DEVELOPED
HOWEVER MAG - INRUSH CURRENT WILL FLOW FOR THE FOLLOWING CONDITION
HOWEVER MAG - INRUSH CURRENT WILL FLOW FOR THE FOLLOWING CONDITION
WHEN A THROUGH FAULT IS CLEAREDWHEN A THROUGH FAULT IS CLEARED
WHEN A LARGE STATION TRANSFORMERCONNECTED TO G T BUSBAR IS ENERGISED WHEN A LARGE STATION TRANSFORMERCONNECTED TO G T BUSBAR IS ENERGISED
GENERATOR PROTECTIONGENERATOR PROTECTION
INTERTURN FAULT PROTECTIONINTERTURN FAULT PROTECTION
LONGITUDINAL DIFFERENTIAL SYSTEM DOES NOT LONGITUDINAL DIFFERENTIAL SYSTEM DOES NOT DETECT INTERTURN FAULTS
INTERTURN FAULT PROTECTION NOT COMMONLY
DETECT INTERTURN FAULTS
INTERTURN FAULT PROTECTION NOT COMMONLYINTERTURN FAULT PROTECTION NOT COMMONLY PROVIDED BECAUSE
FAULTS ARE RARE
INTERTURN FAULT PROTECTION NOT COMMONLY PROVIDED BECAUSE
FAULTS ARE RAREFAULTS ARE RARE
EVEN IF THEY OCCUR THEY WILL QUICKLY
FAULTS ARE RARE
EVEN IF THEY OCCUR THEY WILL QUICKLYEVEN IF THEY OCCUR, THEY WILL QUICKLYDEVELOP INTO STATOR EARTH FAULTSEVEN IF THEY OCCUR, THEY WILL QUICKLYDEVELOP INTO STATOR EARTH FAULTS
GENERATOR PROTECTIONGENERATOR PROTECTION
INTERTURN FAULT PROTECTIONINTERTURN FAULT PROTECTION
HIGH IMPEDANCE TYPE PROTECTIONHIGH IMPEDANCE TYPE PROTECTION
R
Y
B
STABILISING RESISTORRDIFFERENTIAL
RELAY
GENERATOR PROTECTIONGENERATOR PROTECTION
INTERTURN FAULT PROTECTIONINTERTURN FAULT PROTECTION
LOW IMPEDANCE TYPE PROTECTIONLOW IMPEDANCE TYPE PROTECTION
R
Y
B
RDIFFERENTIAL
RELAY
GENERATOR PROTECTIONGENERATOR PROTECTION
INTER TURN FAULT PROTECTIONINTER TURN FAULT PROTECTION
SETTINGSSETTINGS
HIGH IMPEDANCE TYPE PROTECTIONHIGH IMPEDANCE TYPE PROTECTIONSETTINGS RELAY PICK - UP = SHOULD BE LESS THAN
DIFFERENTIAL CURRENT DUE TO
SETTINGS RELAY PICK - UP = SHOULD BE LESS THAN
DIFFERENTIAL CURRENT DUE TO SINGLE TURN SHORT CIRCUIT
Rstab = SAME AS DIFFERENTIAL
SINGLE TURN SHORT CIRCUIT
Rstab = SAME AS DIFFERENTIALRstab = SAME AS DIFFERENTIAL PROTECTION EXCEPTFAULT CURRENT ( If )
Rstab = SAME AS DIFFERENTIAL PROTECTION EXCEPTFAULT CURRENT ( If )FAULT CURRENT ( If )
= MVA x 103
1.732 x KV x Xd’’ x 2
FAULT CURRENT ( If ) = MVA x 103
1.732 x KV x Xd’’ x 2
GENERATOR PROTECTIONGENERATOR PROTECTION
COMBINED DIFFERENTIAL & INTERTURNCOMBINED DIFFERENTIAL & INTERTURN
HIGH IMPEDANCE TYPE PROTECTIONHIGH IMPEDANCE TYPE PROTECTION
R
Y
B
RELAY
GENERATOR PROTECTIONGENERATOR PROTECTION
ZERO SEQ. VOLTAGE MEASUREMENTZERO SEQ. VOLTAGE MEASUREMENT
SHORT CIRCUIT OF ONE OR MORE TURNS WILL CAUSE THE GENERATED E M F TO CONTAIN ZERO SEQUENCE
SHORT CIRCUIT OF ONE OR MORE TURNS WILL CAUSE THE GENERATED E M F TO CONTAIN ZERO SEQUENCETHE GENERATED E M F TO CONTAIN ZERO SEQUENCE COMPONENTTHE GENERATED E M F TO CONTAIN ZERO SEQUENCE COMPONENT
EXTERNAL EARTHFAULTS WILL ALSO PRODUCE A ZERO SEQUENCE VOLTAGE - MOST OF THE VOLTAGE WILL BE EXPENDED ON EARTHING RESISTOR
EXTERNAL EARTHFAULTS WILL ALSO PRODUCE A ZERO SEQUENCE VOLTAGE - MOST OF THE VOLTAGE WILL BE EXPENDED ON EARTHING RESISTORWILL BE EXPENDED ON EARTHING RESISTOR
HENCE, DROP ACROSS THE WINDING SHOULD BE
WILL BE EXPENDED ON EARTHING RESISTOR
HENCE, DROP ACROSS THE WINDING SHOULD BE MEASUREDMEASURED
GENERATOR PROTECTIONGENERATOR PROTECTION
INTERTURN FAULT PROTECTIONINTERTURN FAULT PROTECTION
ZERO SEQUENCE VOLTAGE DETECTIONZERO SEQUENCE VOLTAGE DETECTION
TUNED RELAY SHOUD BE USED
R VR =VA + VB + VC VR =VA + VB + VC
GENERATOR PROTECTIONGENERATOR PROTECTION
STATOR EARTH FAULT PROTECTIONSTATOR EARTH FAULT PROTECTION
CAUSED BY INSULATION FAILURE CAUSED BY INSULATION FAILURE
LEADS TO BURNING OF MACHINE CORE, WELDING OF LAMINATIONS
LEADS TO BURNING OF MACHINE CORE, WELDING OF LAMINATIONS
REBUILDING OF MACHINE CORE CAN BE A VERY EXPENSIVE PROCESS
REBUILDING OF MACHINE CORE CAN BE A VERY EXPENSIVE PROCESSVERY EXPENSIVE PROCESS
HENCE
VERY EXPENSIVE PROCESS
HENCE EARTH FAULT PROTECTION IS A MUSTEARTH FAULT PROTECTION IS A MUST
GENERATOR PROTECTIONGENERATOR PROTECTION
STATOR EARTH FAULT PROTECTIONSTATOR EARTH FAULT PROTECTIONSTATOR EARTH FAULT PROTECTIONSTATOR EARTH FAULT PROTECTION
DEPENDS ON SYSTEM EARTHINGDEPENDS ON SYSTEM EARTHING DEPENDS ON SYSTEM EARTHING
95 % STATOR EARTH FAULT PROTECTION
DEPENDS ON SYSTEM EARTHING
95 % STATOR EARTH FAULT PROTECTION 95 % STATOR EARTH FAULT PROTECTION
100% STATOR EARTH FAULT PROTECTION
95 % STATOR EARTH FAULT PROTECTION
100% STATOR EARTH FAULT PROTECTION
RELAYS WITH INVERSE CHARACTERISTICS PREFERRED
RELAYS WITH INVERSE CHARACTERISTICS PREFERREDPREFERREDPREFERRED
GENERATOR PROTECTIONGENERATOR PROTECTION
95 % S. E. F. PROTECTION - CURRENT OPERATED95 % S. E. F. PROTECTION - CURRENT OPERATED
R ~10 % - 40 %RR
SUITABLE FOR RESISTANCE AND SOLIDLY SUITABLE FOR RESISTANCE AND SOLIDLY EARTHED SYSTEMSEARTHED SYSTEMS
GENERATOR PROTECTIONGENERATOR PROTECTION
95 % S. E. F. PROTECTION - VOLTAGE OPERATED95 % S. E. F. PROTECTION - VOLTAGE OPERATED
~R64
SUITABLE FOR HIGH IMPEDANCE EARTHED SYSTEMSSUITABLE FOR HIGH IMPEDANCE EARTHED SYSTEMS
SHOULD BE A TUNED RELAYSHOULD BE A TUNED RELAY
GENERATOR PROTECTIONGENERATOR PROTECTION
NEED FOR 100 % S. E. F. PROTECTIONNEED FOR 100 % S. E. F. PROTECTION
OVERCURRENT AND OVERVOLTAGE RELAYS WILL NOT DETECT EARTH FAULT NEAR NEUTRALOVERCURRENT AND OVERVOLTAGE RELAYS WILL NOT DETECT EARTH FAULT NEAR NEUTRAL
DIFFERENT METHODSDIFFERENT METHODS
NOT DETECT EARTH FAULT NEAR NEUTRALNOT DETECT EARTH FAULT NEAR NEUTRAL
SUB - HARMONIC INJECTION SUB - HARMONIC INJECTION
THIRD HARMONIC UNDERVOLTAGE THIRD HARMONIC UNDERVOLTAGE
COMPARISON OF THIRD HARMONIC VOLTAGE AT NEUTRAL AND LINE ENDS
COMPARISON OF THIRD HARMONIC VOLTAGE AT NEUTRAL AND LINE ENDS
GENERATOR PROTECTIONGENERATOR PROTECTION
SUB - HARMONIC INJECTION METHODSUB - HARMONIC INJECTION METHOD WILL NOT DETECT OPEN CIRCUITING OF
GROUND TRANSFORMER PRIMARY OR WILL NOT DETECT OPEN CIRCUITING OF
GROUND TRANSFORMER PRIMARY OR SECONDARY
CHANGES THE EARTHING PARAMETERS
SECONDARY
CHANGES THE EARTHING PARAMETERS CHANGES THE EARTHING PARAMETERS WHICH IS NOT DESIRABLE
CHANGES THE EARTHING PARAMETERS WHICH IS NOT DESIRABLE
OFF - LINE SUPERVISION IS REQUIRED
COST OF IMPLEMENTAION AND MAINTENANCE
OFF - LINE SUPERVISION IS REQUIRED
COST OF IMPLEMENTAION AND MAINTENANCE COST OF IMPLEMENTAION AND MAINTENANCE IS VERY HIGH
COST OF IMPLEMENTAION AND MAINTENANCE IS VERY HIGH
GENERATOR PROTECTIONGENERATOR PROTECTION
THIRD HARMONIC UNDERVOLTAGETHIRD HARMONIC UNDERVOLTAGETHIRD HARMONIC UNDERVOLTAGETHIRD HARMONIC UNDERVOLTAGE
SUFFICIENT NEUTRAL THIRD SUFFICIENT NEUTRAL THIRD SUFFICIENT NEUTRAL THIRD HARMONIC VOLTAGE SHOULD BE AVAILABLE
SUFFICIENT NEUTRAL THIRD HARMONIC VOLTAGE SHOULD BE AVAILABLE
IT WILL ALSO BE OUT - OF - SERVICE IF IT WILL ALSO BE OUT - OF - SERVICE IF IT WILL ALSO BE OUT OF SERVICE IF SUFFICIENT VOLTAGE HAS NOT DEVELOPED DURING LIGHTLY LOADED CONDITIONS
IT WILL ALSO BE OUT OF SERVICE IF SUFFICIENT VOLTAGE HAS NOT DEVELOPED DURING LIGHTLY LOADED CONDITIONSCONDITIONS CONDITIONS
GENERATOR PROTECTIONGENERATOR PROTECTION
THIRD HARMONIC VOLTAGE COMPARISONTHIRD HARMONIC VOLTAGE COMPARISON
LINE SIDE AND NEUTRAL SIDE THIRD HARMONIC VOLTAGES ARE COMPARED
LINE SIDE AND NEUTRAL SIDE THIRD HARMONIC VOLTAGES ARE COMPAREDHARMONIC VOLTAGES ARE COMPAREDHARMONIC VOLTAGES ARE COMPARED
V L 3
V N 3 NORMAL CONDITIONNORMAL CONDITIONN 3
GENERATOR PROTECTIONGENERATOR PROTECTION
THIRD HARMONIC VOLTAGE COMPARISONTHIRD HARMONIC VOLTAGE COMPARISONGROUND FAULT AT NEUTRAL END ( VN 3 = 0 )GROUND FAULT AT NEUTRAL END ( VN 3 = 0 )
V L 3V N 3N 3
GENERATOR PROTECTIONGENERATOR PROTECTION
THIRD HARMONIC VOLTAGE COMPARISONTHIRD HARMONIC VOLTAGE COMPARISONGROUND FAULT AT NEUTRAL END ( VN 3 = 0 )GROUND FAULT AT NEUTRAL END ( VN 3 = 0 )
V L 3V N 3N 3
GROUND FAULT AT LINE END ( VL 3 = 0 )GROUND FAULT AT LINE END ( VL 3 = 0 )
V L 3V N 3V N 3
GENERATOR PROTECTIONGENERATOR PROTECTION
FAULT AT 50 % OF GENERATOR WINDINGFAULT AT 50 % OF GENERATOR WINDING
V L 3
V N 3DEAD ZONEDEAD ZONE
THE V L 3 , V N 3 BALANCE WILL BE MAINTAINEDTHE V L 3 , V N 3 BALANCE WILL BE MAINTAINED
V N 3
THE 100 % UNIT MAY NOT DETECTTHE 100 % UNIT MAY NOT DETECT
HENCE , USE A 95 % UNIT ALSOHENCE , USE A 95 % UNIT ALSO
GENERATOR PROTECTIONGENERATOR PROTECTION
100 % STATOR EARTH FAULT100 % STATOR EARTH FAULT
95 % MODULE95 % MODULE100 % MODULE100 % MODULE100 % MODULE100 % MODULE
GENERATOR WINDINGGENERATOR WINDING0 %0 % 100 %100 %
95 % MODULE SHOULD BE CONNECTED TO GROUNDING TRANSFORMER SECONDARY
95 % MODULE SHOULD BE CONNECTED TO GROUNDING TRANSFORMER SECONDARY
SHOULD BE TUNED SHOULD BE TUNED
GENERATOR PROTECTIONGENERATOR PROTECTION
100 % STATOR EARTH FAULT PROTECTION 100 % STATOR EARTH FAULT PROTECTION
DEFINITE TIME DELAYED 100 % UNIT DEFINITE TIME DELAYED 100 % UNIT DEFINITE TIME DELAYED 100 % UNIT
INVERSE TIME DELAYED 0 - 95 % UNIT
DEFINITE TIME DELAYED 100 % UNIT
INVERSE TIME DELAYED 0 - 95 % UNIT
IMMUNITY AGAINST FUSE FAILURE IMMUNITY AGAINST FUSE FAILURE
PROVIDES MONITORING POINTS FOR MEASUREMENT OF OPERATING QUANTITIES
PROVIDES MONITORING POINTS FOR MEASUREMENT OF OPERATING QUANTITIES
USED IN MANY 500 MW AND 210 MW GENERATING SETS USED IN MANY 500 MW AND 210 MW GENERATING SETS
GENERATOR PROTECTIONGENERATOR PROTECTION
UNBALANCED LOADINGUNBALANCED LOADING
GIVES RISE TO NEGATIVE PHASE SEQUENCE STATOR CURRENT WHICH CAUSES CONTRA ROTATINGGIVES RISE TO NEGATIVE PHASE SEQUENCE STATOR CURRENT WHICH CAUSES CONTRA ROTATINGCURRENT WHICH CAUSES CONTRA - ROTATING MAGNETIC FIELDSCURRENT WHICH CAUSES CONTRA - ROTATING MAGNETIC FIELDS
STATOR FLUX CUTS ROTOR AT TWICE SYNCHRONOUS SPEED INDUCING DOUBLE FREQUENCY CURRENT INSTATOR FLUX CUTS ROTOR AT TWICE SYNCHRONOUS SPEED INDUCING DOUBLE FREQUENCY CURRENT INSPEED INDUCING DOUBLE FREQUENCY CURRENT IN FIELD SYSTEM AND ROTOR BODYSPEED INDUCING DOUBLE FREQUENCY CURRENT IN FIELD SYSTEM AND ROTOR BODY
RESULTING . . . . . RESULTING . . . . .
GENERATOR PROTECTIONGENERATOR PROTECTION
UNBALANCED LOADINGUNBALANCED LOADING
RESULTING EDDY CURRENTS CAUSE OVERHEATINGRESULTING EDDY CURRENTS CAUSE OVERHEATING
MACHINES ARE ASSIGNEDI = CONTINUOUS NPS RATING
MACHINES ARE ASSIGNEDI = CONTINUOUS NPS RATINGI2 S = CONTINUOUS NPS RATINGI22 t = SHORT TIME NPS RATING I2 S = CONTINUOUS NPS RATINGI22 t = SHORT TIME NPS RATING
IF SYSTEM UNBALANCE APPROACHES MACHINE CONTINUOUS WITHSTAND THEN PROTECTION IS REQUIRED
IF SYSTEM UNBALANCE APPROACHES MACHINE CONTINUOUS WITHSTAND THEN PROTECTION IS REQUIREDREQUIRED REQUIRED
GENERATOR PROTECTIONGENERATOR PROTECTION
TYPICAL NPS CURRENT WITHSTAND TABLETYPICAL NPS CURRENT WITHSTAND TABLETYPE OF MACHINE TYPE OF COOLING I2 S I22 t
TURBO ALTERNATOR DIRECT HYDROGEN 10 7
TYPE OF MACHINE TYPE OF COOLING I2 S I22 t
TURBO ALTERNATOR DIRECT HYDROGEN 10 7TURBO ALTERNATOR DIRECT HYDROGEN 10 7 30 LB / SQ. FT
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 12
TURBO ALTERNATOR DIRECT HYDROGEN 10 7 30 LB / SQ. FT
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 12TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 12 30 LB / SQ. FT
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 15
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 12 30 LB / SQ. FT
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 15TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 15 15 LB / SQ. FT
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 20
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 15 15 LB / SQ. FT
TURBO ALTERNATOR CONVENTIONAL HYDROGEN 15 20 0.5 LB / SQ. FT
SALIENT POLE CONVENTIONAL AIR 40 60
0.5 LB / SQ. FT
SALIENT POLE CONVENTIONAL AIR 40 60
GENERATOR PROTECTIONGENERATOR PROTECTION
NEGATIVE PHASE SEQUENCE PROTECTIONNEGATIVE PHASE SEQUENCE PROTECTION
I22 t = K
WHERE
I2 = NEGATIVE SEQUENCE COMPONENT
t = WITHSTAND TIME (SECS)
K = CONSTANT PROPORTIONAL TO THEK CONSTANT PROPORTIONAL TO THE THERMAL CAPACITY OF GENERATOR
GENERATOR PROTECTIONGENERATOR PROTECTION
OVERLOAD OVERLOAD
OVER - TEMPERATURE IN STATOR AND ROTOR OVER - TEMPERATURE IN STATOR AND ROTOR
INSULATION FAILURE INSULATION FAILURE
OVERLOAD PROTECTION OVERLOAD PROTECTION
PICK - UP ABOVE THE MAX LOAD CURRENT
ALTERNATIVELY
PICK - UP ABOVE THE MAX LOAD CURRENT
ALTERNATIVELY ALTERNATIVELY ,
CURRENT OPERATED THERMAL REPLICA RELAYS
ALTERNATIVELY ,
CURRENT OPERATED THERMAL REPLICA RELAYS
GENERATOR PROTECTIONGENERATOR PROTECTION
VOLTAGE RELAYSVOLTAGE RELAYSVOLTAGE RELAYSVOLTAGE RELAYS
FIELD EXCITATION SYSTEM USUALLY PREVENTS FIELD EXCITATION SYSTEM USUALLY PREVENTS UNDER- AND OVER- VOLTAGE CONDITIONS
OVER VOLTAGE CONDITION OCCURS WHEN
UNDER- AND OVER- VOLTAGE CONDITIONS
OVER VOLTAGE CONDITION OCCURS WHENOVER - VOLTAGE CONDITION OCCURS WHEN
1 ) PRIME - MOVER OVERSPEEDS DUE TO SUDDEN
OVER - VOLTAGE CONDITION OCCURS WHEN
1 ) PRIME - MOVER OVERSPEEDS DUE TO SUDDEN )LOSS OF LOAD
2 ) VOLTAGE REGULATOR IS DEFECTIVE
)LOSS OF LOAD
2 ) VOLTAGE REGULATOR IS DEFECTIVE2 ) VOLTAGE REGULATOR IS DEFECTIVE2 ) VOLTAGE REGULATOR IS DEFECTIVE
GENERATOR PROTECTIONGENERATOR PROTECTION
OVER VOLTAGEOVER VOLTAGE
ENDANGERS INTEGRITY OF INSULATION
OVERFLUXING
ENDANGERS INTEGRITY OF INSULATION
OVERFLUXINGOVERFLUXING
DEFINITE TIME DELAYED / INVERSE TIME OVERVOLTAGE IS PROVIDED
OVERFLUXING
DEFINITE TIME DELAYED / INVERSE TIME OVERVOLTAGE IS PROVIDEDOVERVOLTAGE IS PROVIDED
UNDER VOLTAGE
OVERVOLTAGE IS PROVIDED
UNDER VOLTAGE
DEFINITE TIME DELAYED UNDERVOLTAGE PROTECTION IS GENERALLY PROVIDEDDEFINITE TIME DELAYED UNDERVOLTAGE PROTECTION IS GENERALLY PROVIDEDIS GENERALLY PROVIDED
BACK - UP FOR OTHER MAIN PROTECTION RELAYS
IS GENERALLY PROVIDED
BACK - UP FOR OTHER MAIN PROTECTION RELAYS
GENERATOR PROTECTIONGENERATOR PROTECTION
FUSE FAILURE PROTECTIONFUSE FAILURE PROTECTION
USED FOR BLOCKING PROTECTION RELAYS USED FOR BLOCKING PROTECTION RELAYS USED FOR BLOCKING PROTECTION RELAYS
PRIMARY AND SECONDARY FUSES SHOULD BE
USED FOR BLOCKING PROTECTION RELAYS
PRIMARY AND SECONDARY FUSES SHOULD BE MONITOREDMONITORED
GENERATOR PROTECTIONGENERATOR PROTECTION
VT FUSE FAILURE PROTECTIONVT FUSE FAILURE PROTECTIONMVAPM32
( 1 )
PT - 1
MVAPM32( 2 )
PT - 2
C1MVAPM32
( 2 )MVAPM32
( 1 )( + ) ( - )
C2MVAPM32
( 2 )MVAPM32
( 1 )
C1 : PT - 1 FAILUREC2 : PT - 2 FAILUREC1 : PT - 1 FAILUREC2 : PT - 2 FAILURE
GENERATOR PROTECTIONGENERATOR PROTECTIONLoss of Excitation
Generator Capability Curve
Loss of Excitation
Can be translated to R-X Plane
( MVA , Ø ) ( Z, Ø )
Z = ( KV2 / MVA ) . ( CTR / PTR ) [ secy.]
KV : Voltage for which the capability curve is valid
GENERATOR PROTECTIONGENERATOR PROTECTIONLoss of ExcitationLoss of Excitation
CausesAccidental tripping of field breaker
Short circuit in the field
P b h t tPoor brush contact
AVR failure
Loss of AC supply to the excitation system
Loss of field to the pilot exciter
GENERATOR PROTECTIONGENERATOR PROTECTIONLoss of ExcitationLoss of Excitation
Consequences Generator damage
Synchronous Induction generator
Slip frequency induced currents rotor heating
High currents stator heating
Stator end iron heating
Hydrogenerators : saliency Hydrogenerators : saliency
GENERATOR PROTECTIONGENERATOR PROTECTIONLoss of ExcitationLoss of Excitation
Consequences Effects on the system
Substantial reactive drain
Consequences Effects on the system
System instability
“ Voltage collapse ”
GENERATOR PROTECTIONGENERATOR PROTECTIONLoss of Excitation
Field Failure Characteristic
Loss of Excitation
Field Failure CharacteristicX
R
Xd’/ 2
Xd
GENERATOR PROTECTIONGENERATOR PROTECTIONL f E it ti
Protection
Loss of Excitation
ProtectionX
R
Xd’/ 2
Xd
GENERATOR PROTECTIONGENERATOR PROTECTIONL f E it ti
Protection
Loss of Excitation
Time delays required for field failure protection
Delay on pick-up Delay on drop-off Delay on drop off
Measuring Element
TDDOTDDO
TDPU
GENERATOR PROTECTIONGENERATOR PROTECTIONPole SlippingPole Slipping
System considerationsSystem considerations
System complexity
Performance criteria
Machine design advancements Machine design advancements
GENERATOR PROTECTIONGENERATOR PROTECTIONPole SlippingPole Slipping
C
Prolonged fault clearing
Causes
Prolonged fault clearing
Excessive system impedances
Underexcited operation
Low system voltage
Line switching operations
GENERATOR PROTECTIONGENERATOR PROTECTIONPole SlippingPole Slipping
Steady - state stability
Response to small and gradual changes in the systemy
P = ( Vs.Vr / X ) Sin Ø
Vs , Vr : sending & receiving end voltagesX : Reactance between Vs and VrØ : Power angle
GENERATOR PROTECTIONGENERATOR PROTECTIONPole SlippingPole Slipping
Consequences High currents, voltage swings
St t i di t Stator winding stress
Pulsating torques Pulsating torques
Transients in the step -up transformer
GENERATOR PROTECTIONGENERATOR PROTECTIONPole Slipping
Characteristics
Pole Slipping
~ ~ZLZA ZB
EA EB
B
ZB
X
ZL
B
P
Z
A
ZA R
GENERATOR PROTECTIONGENERATOR PROTECTIONPole Slipping
Protection - Type ZTO
Pole Slipping
jX
Directional cum blinder
jX
Directional identifiessevere swings
Locus ofPole Slip
Blinder identifies swingsleading to pole - slip
Rleading to pole - slip
Timer distinguishes stableswing
fault conditionsg
GENERATOR PROTECTIONGENERATOR PROTECTIONMotoringMotoring
Failure of mechanical input
SynchronousGenerator
SynchronousMotorGenerator
Prime mover is the main concern
GENERATOR PROTECTIONGENERATOR PROTECTIONMotoring
Prime Mover Motoring Power Possible Damage
Motoring
Diesel Engine 5 % - 25 % Risk of fire or l iexplosion
Gas Turbine 10% - 15 % MechanicalGas Turbine 10% 15 % Mechanical
% % &Hydro - Turbine 0.2 % - 2 % Blade & runner cavitation
Steam turbine 0.5 % - 3 % Thermal stress damage
GENERATOR PROTECTIONGENERATOR PROTECTIONMotoring
Protection Considerations
Motoring
Automatic disconnection
Non-electrical means of protection
Electrical detection Electrical detection
Sensitive reverse power relay p y
Three-phase detection
CT / PT accuracy
GENERATOR PROTECTIONGENERATOR PROTECTIONMotoring
Protection Considerations
Motoring
P
Reverse power relayQVa
High operating angle range
Time delaysTime delays-- Transients-- Asymmetrical faults Ia
Disabling -- Pumped storage schemes-- Synchronous compensation
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal VoltagesAbnormal Voltages
Over voltages Causes
AVR failure
Over voltages - Causes
Operator Errors
Lightly loaded conditions
Load rejection
Hydro generators
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal VoltagesAbnormal Voltages
Overvoltages Consequences Damage to insulation
Overvoltages - Consequences
Over fluxing
Damage to isolated loads
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal VoltagesAbnormal Voltages
Overvoltages ProtectionOvervoltages - Protection
Definite Time relays100 % - 120 % threshold1s - 3s delay1s - 3s delay
Instantaneous relay, if desired 130% - 150 % threshold
GENERATOR PROTECTIONGENERATOR PROTECTIONAb l V l
Undervoltage Function
Abnormal Voltages
Undervoltage Function
A V R failure
B k f l d f lt Back-up for uncleared faults-- Parallel connected generators
Prevents damage to loads
I t l ki Interlocking
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal Frequency
Basics
Abnormal Frequency
Load - frequency link
Load shedding schemes
Relieve overload on generators Relieve overload on generators
Minimise risk of damageg
Minimise possibility of cascading
Restoration of normal frequency
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal FrequencyAbnormal Frequency
Underfrequency - Causes
Loss of GenerationLoss of Generation
S t litS t lit
OverloadOverload UnderfrequencyUnderfrequency
System splitSystem split
Load sheddingLoad shedding
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal Frequency
Under frequency - Consequences
Abnormal Frequency
Generator
Reduced output capability
Thermal damage
Overfluxing
Turbines
Blade stresses
Mechanical resonances
GENERATOR PROTECTIONGENERATOR PROTECTIONAb l FAbnormal Frequency
Prohibited Prohibited operationoperationoperationoperation
Restricted Time Operating Restricted Time Operating Frequency LimitsFrequency Limits
50Continuous operationContinuous operation
uenc
y
ProhibitedProhibited
Restricted Time Operating Restricted Time Operating Frequency LimitsFrequency Limits Fr
eq
Prohibited Prohibited operationoperation
Duration
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal Frequency
Underfrequency - Consequences
q y
q y q
Plant Auxiliaries - Steam Plant Auxiliaries SteamLoss of Capacity at reduced speeds
Pl t A ili i N l Plant Auxiliaries - NuclearCoolant Pump outputs reduced
Combustion Turbines
H d t Hydro generators
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal FrequencyAbnormal Frequency
Under frequency - ProtectionSuggested criteria ( I E E E )
Establish trip points & time delays based on turbine limits
Co-ordination with automated load -shedding
Failure of any single relay should not cause machine trippingmachine tripping
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal Frequencyq y
Under frequency - ProtectionSuggested criteria ( I E E E )
Failure of any single relay should not jeopardise the protection scheme
Scheme should be in operation whenever the unit is synchronised / supplying y pp y gauxiliaries
S t l f d d f / Separate alarms for reduced frequency / pending trip
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal Frequencyq y
Over frequency - Causes
Fault clearingFault clearingFault clearingFault clearing
Over sheddingOver shedding
Loss of LoadLoss of Load
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal Frequencyq y
Overfrequency - Causes
Fault clearingFault clearingFault clearingFault clearing
OversheddingOvershedding Load rejection
Loss of LoadLoss of Load
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal FrequencyAbnormal Frequency
Overfrequency - Causes
Fault clearingFault clearing
Over frequency
Fault clearingFault clearing
OversheddingOvershedding Load rejection
Loss of LoadLoss of Load
GENERATOR PROTECTIONGENERATOR PROTECTIONAbnormal Frequency
Over frequency - Considerations
q y
q y
High speed sets : centrifugal forces High speed sets : centrifugal forces
Control action possiblep
Protection - backup to governor
- Hydroturbines
- Time delays
GENERATOR PROTECTIONGENERATOR PROTECTIONO fl i
CausesOverfluxing
Prior to synchronisation
- Operator / System errors
Failure of excitation system
Loss of nearby generators- Loss of nearby generators
- Operation in overexcited mode
Load rejection
GENERATOR PROTECTIONGENERATOR PROTECTIONOverfluxingOverfluxing
Overexcitation High Flux DensityOverexcitation High Flux Density
GENERATOR PROTECTIONGENERATOR PROTECTIONOverfluxingOverfluxing
Overexcitation High Flux DensityOverexcitation High Flux Density
Saturation of Iron
GENERATOR PROTECTIONGENERATOR PROTECTIONOverfluxingOverfluxing
Overexcitation High Flux DensityOverexcitation High Flux Density
Saturation of Iron
Leakage Paths
GENERATOR PROTECTIONGENERATOR PROTECTIONOverfluxingOverfluxing
Overexcitation High Flux DensityOverexcitation High Flux Density
Saturation of Iron
Leakage Paths
Eddy Currents
GENERATOR PROTECTIONGENERATOR PROTECTIONO fl iOverfluxing
Overexcitation High Flux DensityOverexcitation High Flux Density
Saturation of Iron
Leakage Paths
Eddy Currents
Heat Interlaminar voltage
GENERATOR PROTECTIONGENERATOR PROTECTIONO fl i
ProtectionOverfluxing
Combined with transformer protection
Volts / Hz limiter Volts / Hz limiter
Definite - time relays V Hz
y
Inverse - time relays
t
GENERATOR PROTECTIONGENERATOR PROTECTIONBack up Protection
Voltage Controlled Overcurrent Protection
Back-up Protection
OverloadOverloadCh t i tiCh t i tiCharacteristicCharacteristic
up
Is
Fault Fault CharacteristicCharacteristic
t
t Pic
k -
CharacteristicCharacteristic
Cur
ren
Vs
I Voltage
Vs
GENERATOR PROTECTIONGENERATOR PROTECTIONB k P t ti
Voltage Controlled Overcurrent - Settings
Back-up Protection
Under voltage switching threshold
Voltage Controlled Overcurrent Settings
Under voltage switching threshold
No switching under single phase - earth faults
Should switch for remote - end faults
GENERATOR PROTECTIONGENERATOR PROTECTIONB k P t ti
Voltage Restrained Overcurrent ProtectionBack-up Protection
More suited for indirect connected generatorsg
Equivalent to impedance devices I > k-
upimpedance devices
K I > ent P
ick
Cur
re
VS2 VS1
Voltage
GENERATOR PROTECTIONGENERATOR PROTECTIONBack-up Protection
Voltage Restrained Over current Protection -
Back up Protection
I > : Maximum possible load current
Settings
I > : Maximum possible load current
VS1 : No switching for earth-faults
K I > & VS2 : Should pick - up for remote end feeder faultfault
GENERATOR PROTECTIONGENERATOR PROTECTIONB k P t ti
BasicsBack-up Protection
Subtransient Period Xd’’ , Td’’( 0.1 - 0.2 p.u. )( 0.1 0.2 p.u. )
Transient Period Xd’ , Td’( 0 15 0 35 )( 0.15 - 0.35 p.u. )
Steady - State Period Xd Steady State Period Xd( 1.2 - 1.8 p.u. )
C di ti ith d t lCo-ordination with downstream relays Low pick - up required
GENERATOR PROTECTIONGENERATOR PROTECTIONBack up ProtectionBack-up Protection
Distance Type Back-upDistance Type Back up
~2121
Single zone with mho / offset mho characteristic
GENERATOR PROTECTIONGENERATOR PROTECTIONB k P t tiBack-up Protection
Distance Type Back-upyp p
• Settings
T th l t t i liTo cover the longest outgoing line
Z = ZZ = ZTT + n Z+ n ZLLZ ZZ ZTT n Z n ZLL
ZT = Transformer impedanceT
ZL = Outgoing line impedance
n = Number of parallel connected generators
GENERATOR PROTECTIONGENERATOR PROTECTIONB k P t ti
Back-up Earth fault Protection Back-up Protection
Direct Connected Machines
Indirect Connected Machines51N
Coordination
-- Pickup for remote - end earth faults.
GENERATOR PROTECTIONGENERATOR PROTECTIONB k F il
ConsiderationsBreaker Failure
Faults involving low currents
Abnormal operating conditions
Use high sensitivity detectorsOROR
Use auxiliary contacts from breaker
GENERATOR PROTECTIONGENERATOR PROTECTIONG t T i i
Tripping ModesGenerator Tripping
Class A HV breaker , Field breaker, Turbine, ,For faults in the generator zone
Class B Turbine TripHV Breaker & Field Breaker interlockedHV Breaker & Field Breaker interlocked
with low forward power relay
Class C HV breaker
GENERATOR PROTECTIONGENERATOR PROTECTIONS t Eff t
ConcernsSystem Effects
Shaft Torques
Accidental Energizing
Improper Synchronising
Unbalanced Currents
p ope Sy c o s g
Abnormal Voltages
Transient Instability
Abnormal Voltages
GENERATOR PROTECTIONGENERATOR PROTECTIONS t Eff t
Accidental EnergisationSystem Effects
~Operating Errors
Energisation through the HV disconnect switchHV disconnect switch
- Breaker Head Flashover
Hi h di l t i t S ll t tHigh dielectric stress + Small contact gaps
GENERATOR PROTECTIONGENERATOR PROTECTIONS t Eff t
Accidental Energisation - ConsequencesSystem Effects
Induced Currents
Rapid heating of the rotor surface
Mechanical damage
Hi h i t High primary currents ( Because machine impedance Xd ” )
GENERATOR PROTECTIONGENERATOR PROTECTIONS t Eff t
Accidental Energisation - ProtectionSystem Effects
Voltage Supervised O / C relays
Frequency supervised O / C relays
Auxiliary contact enabled O/C relays
Di t R l Distance Relays
Directional I D M T relays y
GENERATOR PROTECTIONGENERATOR PROTECTIONGenerator Tripping
Device GB FB PM AlarmSuggested Trip L i ( IEEE )
Generator Tripping
87
59G
Logic ( IEEE )
32
40
46
21/51V21/51V
78
8181
64F
GENERATOR PROTECTIONGENERATOR PROTECTIONR t E th F lt
ConsiderationsRotor Earth Faults
First Earth Fault Not Harmful First Earth Fault Not Harmful
Raises the probability of second fault
Second Earth Fault Unbalanced fluxes Second Earth Fault Unbalanced fluxes
Rotor vibration
GENERATOR PROTECTIONGENERATOR PROTECTION
VTUM
U/VVTT 11O RVTUM
VTT11CTIG
VAATD DO
Dead Machine Tripping
CTIG
Backup Tripping
VAA
GENERATOR PROTECTIONGENERATOR PROTECTIONTYPICAL CLASSIFICATION OF TRIPPING
PROTECTIVE RELAY TRIPPING MODE REMARKS
Generator Differential Relay Class ‘A’
TYPICAL CLASSIFICATION OF TRIPPING
Generator Transformer Differential Relay Class ‘A’
Unit Overall Differential Relay Class ‘A’
Generator Stator E/F Relay (100%) Class ‘A’
Generator Stator E/F Relay (95%) Class ‘A’
Generator Transformer Overfluxing Relay Class ‘B’ I stage alarm
Generator Under frequency Relay Class ‘C’ After some time (say 30mins) II stage
I stage alarm30mins) II stage
Generator Rotor Earth Fault Relay Class ‘B’ II stage I stage alarm
Generator Pole slipping Relay Class ‘C’
Generator Field Failure Relay Class ‘B’ Without Under voltage
Generator Low Forward Power Relay For interlock in Class ‘B”tripping
GENERATOR PROTECTIONGENERATOR PROTECTIONTYPICAL CLASSIFICATION OF TRIPPING
PROTECTIVE RELAY TRIPPING MODE REMARKS
Generator Reverse Power Relay Class ‘A’
TYPICAL CLASSIFICATION OF TRIPPING
Generator Distance Backup Impedance Relay Class ‘C’
Generator Voltage Restrained Relay Class ‘A’
Generator Transformer H.V. side Backup O/C relay Class ‘C’
Generator Transformer H.V. side Backup E/F relay Class ‘B’
Unit Auxiliary Transformer Differential Relay Class ‘A’
Generator Negative Sequence Current Relay Class ‘C’ I-stage alarm
Generator Definite time O/C Relay For alarm
Unit Auxiliary Transformer H.V. side O/C Relays (Backuup) Class ‘A’
Generator Transformer Buchholz Relay Class ‘A’ II-stage I-stage alarm
Generator Transformer Winding Temperature Device Class ‘C’ II-stage I-stage alarm
Generator Transformer Oil Temperature Device Class ‘C’ II-stage I-stage alarm
GENERATOR PROTECTIONGENERATOR PROTECTIONTYPICAL CLASSIFICATION OF TRIPPING
PROTECTIVE RELAY TRIPPING MODE REMARKS
Generator Transformer Oil Level Device Alarm
Unit Auxiliary Transformer Buchholz Relay(s) Class ‘C’ I-stage alarm
Unit Auxiliary Transformer(s) Oil Temperature I-stage alarmUnit Auxiliary Transformer(s) Oil Temperature Device(s)
I-stage alarmII-stage-trip unit switch gear incomer breaker(s) and Auto change-over to station service
Unit Auxiliary Transformer(s) Oil TemperatureDevices
I-stage alarmII-stage-trip unit switch gear incomer breaker(s) and Auto change-over.
Unit Auxiliary Transformer(s) Oil Level Device Alarm