Gen Protn Philosophy&Settings
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8/12/2019 Gen Protn Philosophy&Settings
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
CLASSIFICATION OF TRIPPING
CLASSIFICATION OF TRIPPING
Objective is to trip only the absolutely essential so that
- Damage is minimum
- Overspeeding of the TG due to sudden load throw off is avoided
- Impact of tripping of large set on the grid is minimum
- Auxiliaries if possible are kept energised and time to restart the unit is
minimum
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
CLASS-A TRIPPING
CLASS-A TRIPPING
This is adopted for those electrical faults of Generator and Generator
transformer and unit auxiliary transformer for which tripping can not
be delayed.
This leads to simultaneous tripping of
- Generator Transformer HV side CB
- Field Circuit Breaker
- LV side incomer breakers of UAT
- Auto changeover from unit to station for unit auxiliaries and
tripping of turbine
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
CLASS-B TRIPPING
CLASS-B TRIPPING
This is adopted for all turbine faults (Mechanical) and for some
electrical faults of Generator, Generator transformer and unit auxiliary
transformer for which it is safe to trip the turbine.
Subsequently the Generator is tripped through low forward power
interlock
Ensures that unit does not overspeed due to trapped steam in the
turbine during the shutdown and also the loss of power to the grid from
the Generator is not sudden.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
CLASS-C TRIPPING
CLASS-C TRIPPING
This is adopted for all faults beyond the Generator system which can be
cleared by tripping of Generator transformer HV side CB alone.
In this case the TG set runs with HP-LP bypass system in operation and
the Generator continues to feed the unit auxiliary load through unit
auxiliary transformers.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Class CGenerator Pole slipping Relay
Without Under voltageClass BGenerator Field Failure Relay
I stage alarmClass B II stageGenerator Rotor Earth Fault Relay
I stage alarmClass C After some
time (say 30mins) II stage
Generator Under frequency Relay
I stage alarmClass BGenerator Transformer Overfluxing Relay
Class AGenerator Stator E/F Relay (95%)
Class AGenerator Stator E/F Relay (100%)
Class AUnit Overall Differential Relay
Class AGenerator Transformer Differential Relay
For interlock in Class B
tripping
Generator Low Forward Power Relay
Class AGenerator Differential Relay
REMARKSTRIPPING MODEPROTECTIVE RELAY
TYPICAL CLASSIFICATION OF TRIPPING
TYPICAL CLASSIFICATION OF TRIPPING
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
I-stage alarmClass C II-stageGenerator Transformer Winding Temperature Device
Class AUnit Auxiliary Transformer H.V. side O/C Relays (Backuup)
I-stage alarmClass A II-stageGenerator Transformer Buchholz Relay
For alarmGenerator Definite time O/C Relay
I-stage alarmClass CGenerator Negative Sequence Current Relay
Class AUnit Auxiliary Transformer Differential Relay
Class BGenerator Transformer H.V. side Backup E/F relay
Class CGenerator Transformer H.V. side Backup O/C relay
Class AGenerator Voltage Restrained Relay
Class CGenerator Distance Backup Impedance Relay
I-stage alarmClass C II-stageGenerator Transformer Oil Temperature Device
Class AGenerator Reverse Power Relay
REMARKSTRIPPING MODEPROTECTIVE RELAY
TYPICAL CLASSIFICATION OF TRIPPINGTYPICAL CLASSIFICATION OF TRIPPING
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
TYPICAL CLASSIFICATION OF TRIPPINGTYPICAL CLASSIFICATION OF TRIPPING
AlarmUnit Auxiliary Transformer(s) Oil Level Device
I-stage alarm
II-stage-trip unit switch
gear incomer breaker(s)
and Auto change-over.
Unit Auxiliary Transformer(s) Oil Temperature
Devices
I-stage alarm
II-stage-trip unit switch
gear incomer breaker(s)
and Auto change-over to
station service
Unit Auxiliary Transformer(s) Oil Temperature
Device(s)
I-stage alarmClass CUnit Auxiliary Transformer Buchholz Relay(s)
AlarmGenerator Transformer Oil Level Device
REMARKSTRIPPING MODEPROTECTIVE RELAY
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
TYPICAL GROUPING OF RELAYSTYPICAL GROUPING OF RELAYS
GROUP-I
- Generator Differential Relay
- Generator Transformer Differential Relay
- Generator Stator Earth Fault Relay for protection of 100% stator winding
- Generator Over-voltage Relay
- Generator Underfrequency Relay
- Generator Rotor Earth Fault Relay
- Generator Field Failure Relay
- Generator Low Forward Power Relay
- Generator Reverse Power Relay
- Generator voltage restrained O/C Relay
- Generator Transformer HV side O/C Relay (for backup protection)
- Unit Auxiliary Transformer(s) Differential Relay(s)
- Generator Negative Phase Sequence Current Relay
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
TYPICAL GROUPING OF RELAYSTYPICAL GROUPING OF RELAYS
GROUP-II
- Unit overall Differential Relay
- Generator Stator Earth Fault Relay for protection of 95% startor winding.
- Generator Transformer Overfluxing Relay
- Generator Overvoltage Relay.
- Generator Rotor Earth Fault Relay.
- Generator Field Failure Relay.
- Generator Pole Slipping Relay.
- Generator Low Forward Power Relay.
- Generator Reverse Power Relay.
- Generator Distance Backup Relay.
- Generator HV standby Earth Fault Relay.
- Unit Aux Transformer(s) H.V. side overcurrent Relay (for back up protection)
- Generator Negative Phase Sequence Current Relay.
- Generator definite time over-current Relay.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GeneratorData :
Rated MVA : 247 MVA
Rated kV : 15.75kV
Full load current : 9065A
Sub-transient Reactance Xd : 21.4%
Neutral Grounding Transformer :
25 kVA, 15.75 kV/240 V, Resistor: 0.5 ohms, 280A.
Field Circuit Voltage : 600V
Negative Sequence Particulars :
1) A symmetrical short circuit performance is given by 12t 2) Continuous negative sequence withstand current of generator-5%
which implies that maximum difference between the line current
is about 10%.
SYSTEM DETAILSSYSTEM DETAILS
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
b) 400 kV side CT : 500/ 1 A, RCT= 3 , Vk=1000 V
class PS, star connection
c) Neutral side CT : 500/1 A, PS, Vk=1000 V,RCT=3
3) RLLead resistance : One way lead resistance of 15 m, 2.5 mm2
single cable is 0.1 (looping done in CT
Marshalling box)
SYSTEM DETAILSSYSTEM DETAILS
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Relay particulars:
Type : RAGEA
RXIG 95% Relay : 5-15V; 50 Hz.
RXIG 100% Relay : 0.4-1.2V, 150 Hz.
RXEG Supervision Relay : 40-120 V
RXKE1 for 95% Element : 20ms-99s
RXKE1 for 100% Element : 20ms- 99s
Auxiliary Voltage : 220 V DC
GENERATOR 100% EARTH FAULT RELAYGENERATOR 100% EARTH FAULT RELAY
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Calculations:
95% Element:
When a fault occurs on the high voltage side of a / Y step-up transformer,There is no voltage
displacement of the generator neutral due to Zero Sequence currents. But still a small generatorneutral voltage exists for an External ground fault due to a small capacitive coupling between
primary and secondary of the generator step-up transformer. If the data to Calculate this small
neutral voltage is not available, then relay sensitivity Is restricted to about 4-5%.
Also, the 95% relay of RAGEA is suitable for operation at lower frequency and thus can act as a
reliable earth fault protection during start-up. It Operates with increased sensitivity down to about
25 Hz, the operating value being about 0.6x set voltage. At still lower frequency of 10Hz, the relay
operates at 0.8 x set voltage.
Secondary side voltage of grounding transformer for a fault on generator terminal is 240/ 3 = 138V.
From experience it is found that, a setting of 5.4 V of the voltage gives adequate discrimination
against such faults.
GENERATOR 100% EARTH FAULT RELAYGENERATOR 100% EARTH FAULT RELAY
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Time delay setting need to be selected considering PT fuse operating time in case of a fault ongenerator PT. This delay also gives stability against relay picking up from stray voltages.
Delay of about 1-2 secs is recommened.
100% Element:
Setting of this relay is approx. 50% of 3rdharmonic voltage measured across the Generator
grounding transformer.
Typical value of this 3rdharmonic voltage = 1-2V
Setting should be adjusted at site depending on actual measured value.
Time delay of 2 secs. Can be set.
Supervision Relay:
This is usually set about 80% of rated voltage, approx. 90 V.
GENERATOR 100% EARTH FAULT RELAYGENERATOR 100% EARTH FAULT RELAY
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Recommended Settings :
95% Relay : 5.4 V,1 sec.
100% Relay : 0.5 V, 2 sec.
Supervision Relay : 90 V
GENERATOR 100% EARTH FAULT RELAYGENERATOR 100% EARTH FAULT RELAY
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Rated MVA = 247 MVA
Rated kV = 15.75 kV
Rated Load Impedance = 15.75/ 247 = 1.0043 prim.
CTR / PTR = ( 10000 / 5 ) / ( 15.75 x 10/ 110 ) = 13.97
Setting of RAKZB = 70 % of Rated Load Impedance
= 0.7 x 1.0043 x 13.97 = 9.82sec.
Forward Reach = Reverse Reach
ZF= ZR= 9.82 sec.
ZF= ZR= ( 0.2 f / la 3 ) x ( A / B ) f = 50 Hz. Ia= ln= 5 A
( A / B ) = 8.5
Choose A = 80, then B = 9.4
GENERATOR BACK-UP IMPEDANCE PROTECTION-RAKZBGENERATOR BACK-UP IMPEDANCE PROTECTION-RAKZB
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Type : RXNB
Operating Value : Approx. 5 Kat Ux = 0 V and
: Approx. 245 Kat Ux = 600 V
The relay operates for an insulation resistance Rxdependent upon Uxwhen
( ( Ux+ 48 ) / 2.5 ) 14 K= Rx
U1 : supply Voltage
Um : Super imposed voltage between the negative pole of the field
winding and the earth
Ux : Field voltage between the fault location & negative pole of the field wdg.
Rx : Insulation Resistance between the field windind & the earth at the fault
location.
Ij : Current in the measuring circuit.
ROTOR EARTH FAULT RELAY- RXNBROTOR EARTH FAULT RELAY- RXNB
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
ROTOR EARTH FAULT RELAY- RXNBROTOR EARTH FAULT RELAY- RXNB
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Delay on pick-up : Approx. 11sec.
Maximum permissible
Field circuit voltage : 600V continuous, 1500v for 9 sec Bias circuit voltage : 240VK10%, 50Hz.
Auxiliary voltage : 240V DC
Recommended settings :
The relay has fixed settings as described.
ROTOR EARTH FAULT RELAY- RXNBROTOR EARTH FAULT RELAY- RXNB
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR NEGATIVE SEQUENCE PROTECTION (RARIB)GENERATOR NEGATIVE SEQUENCE PROTECTION (RARIB)
Relay particulars:
Type : RARIB
Operating according to t : (In / I2) K where In = rated primary current of Auxiliary CT
K = 1-63secs.
Operating value start : 4-16%
Alarm element : 3-9%
Time delay of alarm : 6secs.
Cooling down time : (K x 170)/2 where a is a constant which is internally
reconnectible in complete steps between 0 and 6
Auxiliary Voltage : 220 V DC
CT details : 10000/5A
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR NEGATIVE SEQUENCE PROTECTION (RARIB)GENERATOR NEGATIVE SEQUENCE PROTECTION (RARIB)
Calculations:
Secondary current corresponding to full load = 4.53A
Setting IM= (4.53/5) x In= 0.906 Inwhere Inis set to 5A.
Recommended settings:
IM = 0.906 x 5AK = 8 on relay (System Details)
Alarm relay = 4% of IM
Trip relay = 8% of IM
Time lag relay for delayed alarm : 6secs.
Cooling down time constant : 2.6 x K
In the absence of valid data of the machine, this has been set at the lowest value.
This is not field adjustable.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR DIFFERENTIAL RELAYGENERATOR DIFFERENTIAL RELAY
Relay Particulars :
Type : RADHA
Rating : 5A
Operating Voltage : 40/50V
Operating Current : 20mAAuxiliary Voltage : 220V DC
System Details :
CT Details : 10000/5A, RCT=1.5
Vk=600V
CT lead resistance RL : Pilot wire loop resistance from CT to interconnection point
of CT leads at Bus duct=0.2 (One way length is 15m,
2.5mmcs)
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR DIFFERENTIAL RELAYGENERATOR DIFFERENTIAL RELAY
Calculations:
1) Maximum through fault current = 1/Xd = 1/0.214=4.67 pu
Base Current = 9.065KA If= 4.67 x 9.065KA = 42.33KA
CT sec. Current Ik= 21.2A
Maximum rms voltage that will develop across the relay for this through fault
current = Ik(RCT+RL)
= 36.04V
Normally a setting of 110% of this voltage will provide full stability against external
fault.
1.1 x 36.04 = 39.65V
A relay version of 40-50V to be selected & to be set at 40 V
Minimum knee point voltage requirement : Vk= 2 x 40 = 80V
Minimum Primary operating current : Ip= n1(IR+ Im+ Ires)
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR DIFFERENTIAL RELAYGENERATOR DIFFERENTIAL RELAY
Where IR = Relay operating current = 0.02A
Im = Magnetising current of CT at set value
= 0.005 A (assumed)
Ires = 5mA for MXA 983-B at 70V
Ip = 10000/5 (0.02 + 0.05 + 0.005) = 150A
Recommended settings:
40 V
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
LOSS OF EXCITATION RELAY (RAGPC)LOSS OF EXCITATION RELAY (RAGPC)
Relay particulars:
Type : RAGPC
Rating : 5A
Scale Ranges : RXPE40 Directional Relay : 1-4A
: RXIG Overcurrentl Relay : 2.5-7.5A
: RXEG2 Under Voltage Relay : 40-120V
System Particulars:
The generator is capable of delivering 247 MVA continuously at 15.75kV terminal
voltage, 9065 A stator current and 3 kg/cmhydrogen pressure with cold gastemperature not exceeding 40C and distillate termperature at inlet of stator wdg notexceeding 40C. The generator capability curve is as per enclosed diagram.
CT Details : 10000/5A, RCT=1.5 , Vk=600V, Class : PS
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
LOSS OF EXCITATION RELAY (RAGPC)LOSS OF EXCITATION RELAY (RAGPC)
PT Details : 15.75kV /110V, 200VA, 3P / 0.5M
Calculations:
The characteristic of RXPE40 unit super- imposed on generator capability curve is
shown in the diagram. The setting of RXPE should correspond to about 70 MVA
as can be seen from the diagram.This corresponds to a secondary current of 1.28A.
The undervoltage and overcurrent relays are usually set at about 85% of Unand 115%
if Inrespectively.
Recommended settings:
For under voltage relay RXEG2
Setting Range : 85-90% of Un(=110 V)
Recommended Setting : 95V (86% of Un)
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
LOSS OF EXCITATION RELAY (RAGPC)LOSS OF EXCITATION RELAY (RAGPC)
2) For Overcurrent relay RXIG2
Setting Range : 110-115% of In(=5A)
Recommended Setting : 5.75A (115% of In)
3) For Directional relay RXPE40
Recommended Setting : 1.28A
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR CAPABILITY CURVE & LOSS OF EXCITATION RELAY CH.GENERATOR CAPABILITY CURVE & LOSS OF EXCITATION RELAY CH.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAYGENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAY
Relay particulars:
Type : RADSB
Rating : 5A
Auxiliary Voltage : 220 V DC
Restraint Operating value : Settable at 20, 25, 32, 40 or 50% of In
Unrestraint Operating value : Reconnectible to 8, 13 0r 20 times In
Calculations:
For determining auxiliary Ct requirement
In1on 15,75 kV side = (250 x 10) / (3 x 15.75)KA
= 9164.56A
In2on 420 kV side = (250 x 10) / (3 x 420)KA
= 343.67A
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAYGENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAY
In1= (5/10000) x 9164 = 4.58A
In2= (1/500) x343.7 = 0.687
Ratio of auxiliary CT = 0.687 / (4.58/ 3 )
= 0.687 / 2.64
Vk=30 x In (RICTS) = 30 x (5/ 3) x RICTS
= 30 x RICTS
Setting Calculations:
a) Operating current setting :
Maximum tap changing position : 5%
According to the designers recommendation a minimum current sensitivity of
about 15% greater than the worst turns ratio mismatch at the tap changer should
normally be selected.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAYGENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAY
Therefore, for 5% variation of taps operating current setting of 20% gives enough
margin for CT unbalance and other errors.
b) Unrestricted operating current setting:
This feature is to provide instantaneous tripping in the event of severe internal
faults.
Recommended unrestrained relay setting to take care of inrush currents on
switching, from experience based on full load current equal to normal relay rating.
In pratice such a situation arises in case of this transformer when an external
close-in fault is cleared.
13 % 13%
When energised from
HV side LV side
Y-(LV) Any
Transformer Transformer
Connection Size
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAYGENERATOR TRANSFORMER OVER-ALL DIFFERENTIAL RELAY
Recommended settings:
Maximum pick-up current setting = 20% of In
Unrestrained operating current setting = 13 times In
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER HV WINDING RESTRICTED EARTH
FAULT RELAY
GENERATOR TRANSFORMER HV WINDING RESTRICTED EARTH
FAULT RELAYRelay particulars:
Type : RADHD
Rating : 1A
Operating Voltage : 10/15V
Operating Voltage : 20mAAuxiliary Voltage : 220V DC
Calculations:
Maximum through fault current = (250 x 1) / (3 x 420 x 0.145)
= 2370A
If = 2370 / 500 = 4.74A
Minimum relay = If (RCT+ 2RL) = 4.74 (3 + 0.2)
Operating Voltage = 15.17V
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER HV WINDING RESTRICTED EARTH
FAULT RELAY
GENERATOR TRANSFORMER HV WINDING RESTRICTED EARTH
FAULT RELAY
Thus, setting can be = 15V
Minimum Knee point voltage of CT = =2 x 15V = 30V
Recommended settings:
Voltage setting = 15V
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER OVER-FLUXING RELAYGENERATOR TRANSFORMER OVER-FLUXING RELAY
Relay particulars:
Type : RATUB
Rating : 110V, 50Hz AC
Setting Range : Start, Alarm 1.5 to 3V / Hz
Calculations:
Following are some comments regarding setting of RATUB
1 ) Transformer can withstand 10% of rise in V /Hz continuously
Therefore setting U/ f start can be selected as
1.09 x (Un/fn) = 1.09 x (110/50) = 2.4V/Hz
2) Plot of transformer U/f withstand characteristics on RATUB characteristics gives
K = 2 as the one giving
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER OVER-FLUXING RELAYGENERATOR TRANSFORMER OVER-FLUXING RELAY
Operating times lower than transformer withstand time for rise in U/f up to
1.35 x (Un/fn). Characteristics of transformer super-imposed on relay characteristics
is shown in diagram.
3) Beyond 1.35 x (Un/fn) rise in U/f operating time of RATUB varies from 6 to 2.2 secs at
K=2, whereas transformer requires instantaneous tripping. Usually instantaneous
element of O/V relay set suitably takes care of these conditions.
4) Alarm unit can be set at same value as trip, 2.4V/Hz and time setting can be at
3.5 secs.
However if instantaneous tripping is desired from RATUB itself alarm unit can be
used for this purpose in which case setting of this unit will be 1.35 x (Un/fn)=1.35 x
(110/50) = 3V/Hz with delay set at 0.1 secs.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
GENERATOR TRANSFORMER OVER-FLUXING RELAYGENERATOR TRANSFORMER OVER-FLUXING RELAY
Recommended settings:
(U / f) start = 2.4V / Hz
K = 2
(U / f) alarm = 2.4V / Hz with time delay 3.5 secs.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
THE OPERATING TIME t AS A FUNCTION OF THE RELATIONSHIP BETWEEN THE ACTUAL
EXCITATION ANS THE SET STARTING VALUE, FOR DIFFERENT TIME CONSTANTS K.
THE OPERATING TIME t AS A FUNCTION OF THE RELATIONSHIP BETWEEN THE ACTUAL
EXCITATION ANS THE SET STARTING VALUE, FOR DIFFERENT TIME CONSTANTS K.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
INTERTURN FAULT PROTECTIONINTERTURN FAULT PROTECTION
Relay particulars:
Type : RXIG28
Range : 5-15V
Aux PT details:
PT-1 : 145.5V/200V, 3P, 15VA
PT-2 : 3.25V/65V, 3P, 15VA
Calculations:
Voltage per turn per slot = 131.25V
In case of split windings
Vfor a single turn fault = 131.25/2=65.645V
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
INTERTURN FAULT PROTECTIONINTERTURN FAULT PROTECTION
VBA = 65.625 *(110/3) *[3/(15.74*10)]
VCD = 0.46 *65/3.25 = 9.2V
The relay can be set at 50% of the voltage developed across the relay for a single turn
Fault.
Recommended Setting:
RXIG28 setting = 5V
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
LIST OF REQUESTED PROTECTIVE FUNCTIONS * DIVIDED
UP INTO TWO SYSTEMS
LIST OF REQUESTED PROTECTIVE FUNCTIONS * DIVIDED
UP INTO TWO SYSTEMS
A B
X
X
X
X
X
X
X
X
X
Generator Differential
Over all Differential
Minimum Impedance
(or alternatively)Overcurrent/Undervoltage
(for thyristor excitation)
(or option)
Overcurrent
Negative sequence
Thermal90% Stator Earth Fault
Neutral Disp.
100% stator earth fault
87G
87T
21
51/27
51
46
4959
64
Generator stator
Short circuits
Assymetry
Stator overload
Earth fault stator
SYSTEMPROTECTION FUNCTIONSANSITYPE OF FAULT
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
A B
X
X
X X
X
X X
X
X
X
X X
Mini reactance
Pole slip
Reverse power (double protection for large
Generators)
Max. frequency
Min. frequencyOvervoltage or overcurrent
Undervoltage
Overfluxing Volt/Hz
Overvoltage
ThermalBridge measuring hardware combined with
Voltage function
40
78/21
32
81
8159
27
24
59
4964R
Generator stator
Loss of excitation
Out of step
Monitoring
Over speed
Blade fatigueInterturn fault
Lower voltages
Mag. Circuit
Higher voltage
Generator Rotor
Rotor OverloadRotor ground
SYSTEMPROTECTION FUNCTIONSANSITYPE OF FAULT
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
Example : Definite list must be prepared in accordance with electrical scheme andinstallation requirements.
A B
X
X
X
X
X
X
X
X
X
Transformer Differential
Overcurrent
Earth Fault Overcurrent
Restricted Earth Fault
Transformer Differential
Overcurrent
Overload
Residual Overcurrent (possible option in
acc. With requirements)
Restricted Earth Fault (possible option in
acc. With requirements)
87T
50/51
51N
87N
87T
50/51
49
(51N)
(87N)
Step-up Transformer
Short circuit
Ground Fault
Unit Transformer
Short circuit
Ground Fault
SYSTEMPROTECTION FUNCTIONSANSITYPE OF FAULT
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
1) Generator differential protection 87G-RADHA:
a) Sub-transient reactance Xd
b) CT secondary resistance RCT
c) Lead resistance from CT to junction point RL
2) Differential protection 87L-RADHA:
a) Sub-transient reactance Xd
b) Transformer reactance XT
c) CT secondary resistance RCT
d) Lead resistance from CT to junction point RL
3) 100% Earth fault relay 64G1-RAGEA:
a) 3rdHarmonic voltage across secondary of grounding transformer.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
4) Generator Overvoltage relay - 59G-RXEG:
a) Overvoltage withstand values of the generator.
5) Generator Inter-turn fault relay 50GI-RXIG:
a) Unbalance in current for 1 turn short circuit.
6) Loss of Excitation relay 40G-RAGPC:
a) The generator capability curve.
b) Impedance locus during loss of excitation
c) Variation in machine voltage & current on loss of excitation
7) Negative sequence protection 46G-RARIB:
a) K- A constant in seconds that is the characteristic for the generator
This constant represents the time during which a negative
sequence current that is equivalent to the rated current of the
generator, can be permitted.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
b) Continuous negative sequence withstand value.
8) Under-frequency protection- 81G-RXFE:
a) Generator manufacturers recommendations regarding under frequency
trip.
9) Over current relay 51-RXIG:
a) Continuous withstand current of the unit.
10) Generator Backup Impedance relay 21G-RAKZB:
a) Philosophy adopted for setting:
- to cover only transformer
- to cover next outgoing line but not beyond, under all
generation conditions
- to set for 70% of maximum load impedance.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
11) Pole slipping relay:
a) Impedance locus during pole slip.
12) Over-all differential relay 87GT-RADSB:
a) RCT, Vkof main CT.
b) RL, Lead Resistance.
13) Restricted Earth fault relay 64GT-RADHD:
a) RCTof the main CT.
b) RL, Lead Resistance.
14) Over fluxing relay 99GT - RATUB:
a) Over fluxing characteristics of the transformer.15) Transformer Ground fault relay 51NGT-CDG:
a) Plug setting.
b) Time setting.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
DATA REQUIRED FOR RELAY SETTING CALCULATIONS FOR
GENERATOR PROTECTIONS
16) Station Transf. Differential relay 87UTA & 87UTB-RADSB:
a) RCT, Vkof main CT.
b) RL, Lead Resistance.
17) Station Transf. Overcurrent relay 51UTA CDG33:
a) Plug setting.
b) Time setting.
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GENERATOR PROTECTION Combiflex R
ABB India
Utilities - Automation