generator protections basics

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


PRIME MOVERSPRIME MOVERSPRIME MOVERSPRIME MOVERS

STEAM TURBINESSTEAM TURBINESSTEAM TURBINES

GAS TURBINES

STEAM TURBINES

GAS TURBINES

HYDROHYDRO

DIESELDIESEL


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


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

~


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

~~


METHOD OF EARTHINGMETHOD OF EARTHINGSOLIDSOLID



RESISTANCERESISTANCE RRESISTANCERESISTANCE R



RESISTANCERESISTANCE RRESISTANCERESISTANCE R

HIGH IMPEDANCEHIGH IMPEDANCE R


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


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


DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTION

HIGH IMPEDANCE TYPE HIGH IMPEDANCE TYPE

~Differential Relay

Stabilising Resistor

ZG9323

g


DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONHIGH IMPEDANCE TYPEHIGH IMPEDANCE TYPE

~RCT

If RCT

2RV

2RL


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



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



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


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



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


DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONLOW IMPEDANCE TYPELOW IMPEDANCE TYPE

~

BIAS COIL

BIAS COILOPERATING COILZG9323

BIAS COIL



LOW IMPEDANCE TYPELOW IMPEDANCE TYPE

OPERATEOPERATENT

NT

OPERATEOPERATE

UR

REN

UR

REN

RESTRAINRESTRAIN

DIF

F. C

DIF

F. C

BIAS CURRENT BIAS CURRENT

DD


DIFFERENTIAL PROTECTIONDIFFERENTIAL PROTECTIONOVERALL DIFFERENTIAL PROTECTION SCHEMEOVERALL DIFFERENTIAL PROTECTION SCHEME

~ G TG T

UAT

ICTRELAY


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


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



HIGH IMPEDANCE TYPE PROTECTIONHIGH IMPEDANCE TYPE PROTECTION

R

Y

B

STABILISING RESISTORRDIFFERENTIAL

RELAY



LOW IMPEDANCE TYPE PROTECTIONLOW IMPEDANCE TYPE PROTECTION

R

Y

B

RDIFFERENTIAL

RELAY


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


COMBINED DIFFERENTIAL & INTERTURNCOMBINED DIFFERENTIAL & INTERTURN

HIGH IMPEDANCE TYPE PROTECTIONHIGH IMPEDANCE TYPE PROTECTION

R

Y

B

RELAY


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



ZERO SEQUENCE VOLTAGE DETECTIONZERO SEQUENCE VOLTAGE DETECTION

TUNED RELAY SHOUD BE USED

R VR =VA + VB + VC VR =VA + VB + VC


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


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


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


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


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


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


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


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


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


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


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


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


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


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 . . . . .


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


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 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 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


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


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


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


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


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


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


Consequences Generator damage

Synchronous Induction generator

Slip frequency induced currents rotor heating

High currents stator heating

Stator end iron heating

Hydrogenerators : saliency Hydrogenerators : saliency


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


C

Prolonged fault clearing

Causes

Prolonged fault clearing

Excessive system impedances

Underexcited operation

Low system voltage

Line switching operations


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


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


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


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


Overvoltages Consequences Damage to insulation

Overvoltages - Consequences

Over fluxing

Damage to isolated loads


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


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


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


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


Over frequency - Causes

Fault clearingFault clearingFault clearingFault clearing

Over sheddingOver shedding

Loss of LoadLoss of Load


Overfrequency - Causes

Fault clearingFault clearingFault clearingFault clearing

OversheddingOvershedding Load rejection



Overfrequency - Causes

Fault clearingFault clearing

Over frequency

Fault clearingFault clearing

OversheddingOvershedding Load rejection



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



Saturation of Iron



Saturation of Iron

Leakage Paths



Saturation of Iron

Leakage Paths

Eddy Currents

GENERATOR PROTECTIONGENERATOR PROTECTIONO fl iOverfluxing


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


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


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


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


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


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 ” )


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


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 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 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

generator protections basics

Documents

generator protectiono fl

generator protectionpole slipping

generator protectiontypical classification

generator protectionabnormal voltages

system effects eff

generator protectionabnormal frequency

generator protectionl loss

stage alarm ii