GENERATOR PROTECTION GENERATOR PROTECTION TYPES OF PROTECTION TYPES 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
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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
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
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
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
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
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
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
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