Download - Generator Numerical Protection System
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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2. TECHNICAL DATA
Generator:
GENERATOR OUTPUT= Sn 55560.00 kVARATED VOLTAGE= Un 11 kVPOWER FACTOR p.f. 0.9RATED CURRENT In 2915.9 ARATED FREQUENCY fn 50 HzSYNCRONOUS REACTANCE Xd 93.30%TRANSIENT REACTANCE (STAURATED) Xd' 26%NEGETIVE PHASE SEQUENCE WITHSTAND I2 8%UNBALANCED LOAD (I2/IN)xt 20 secFIELD CURRENT If 875 AdcSTATOR LEAKAGE REACTANCE xs 0.0952 PUSYNCRONOUS REACTANCE QUARD AXIS Xq 0.602 PU
Step up transformer
RATED VOLTAGE Un 11/132 kVRATED OUTPUTS Sn 63.9 MVASHORT CIRCUIT VOLTAGE Uk 12.5 %VECTOR GROUP YNd11
Auxiliary Transformer :
RATED VOLTAGE Un 11000/415 VRATED OUTPUTS Sn 500 KVAVECTOR GROUP Dyn11
Excitation Transformer :
RATED VOLTAGE Un 11000/364 VRATED OUTPUTS Sn 630 KVAVECTOR GROUP Dy5
Line Parameters:
POSITIVE SEQUENCE RESISTANCE R1 0.14 OHMS/KMPOSITIVE SEQUENCE REACTANCE X1 0.387 OHMS/KMZERO SEQUENCE RESISTANCE R0 0.272 OHMS/KMZERO SEQUENCE RESISTANCE X0 1.233 OHMS/KMLINE LENGTH L 70 KMLENGTH OF NEXT SHORTEST LINE L1 30 KMLENGTH OF NEXT LONGEST LINE L2 30 KM
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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Current Transformer Primary Secondary
GENERATOR TRANSFORMER HV SIDE 400A 1AGENERATOR TRANSFORMER NEUTRAL 400A 1AGENERATOR NEUTRAL 4000A 5AGENERATOR TERMINAL 4000A 5AAUX TRANSFORMER HV SIDE (OVERALL DIFF) 4000A 5AGENERATOR TRANSFORMER HV SIDE (DIFF) 600A 1AAUX TRANSFORMER HV SIDE (OVERCURRENT PROT) 100A 1A
Voltage transformer Primary Secondary
PROTECTION CORE 11000V 110VAVR CORE 11000V 110VNEUTRAL TRANSFORMER 11000V 110VMETERING CORE 11000V 110VLINE PT 110000V 110V
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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3.GENERATOR, TRANSFORMER AND UNIT AUXILIARY TRANSFORMER PROTECTION
A) GENERATOR DIFFERENTIAL PROTECTION 87G
This function protects the generator system from the neutral CTs to the generator terminal CTs. When function operates, the unit will be shut down immediately.
The differential setting value is calculated as follows:
555602916.14
3 11 3gp
Sn kVAI A
Un kV
Generator primary current
Now with a CT ratio = 4000/5 A the generator secondary current is calculated
2916.14A5 3.65
4000
gpgs
II A A
CTratio A Generator secondary current
The differential current setting is chosen to be 20% of the relay current rating, i.e.
AAI s 1520.087
This is in turn the equivalent to the generator rated current.
87 1% 100 100 27.4%
3.65
s
gs
I AI
I A
The bias slope is set to %40bias
Setting
Name of parameter
Range
Operate Value 1A Bias 40%
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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B) GENERATOR UNDEREXCITATION PROTECTION 40G
The under excitation MHO protection is used to detect failures in the excitation system of synchronous generators and to prevent damage to the equipment and power swings in the system.
The given direct reactances areSynchronous reactance xd 93.3%Transient reactance (saturated) xd 26%
A compensation factor F must be determined according to the equation below, in order to adjust the reactances to the CT and VT ratios:
11000 4000 110 51.5
2916.14 5 11000 100
G r
G r
V CTratio I V A V AF
I VTratio V A A V V
whereIr rated current of the relayVr rated voltage of the relay (100V internally)
So the adapted reactances are
1.5 0.933 1.399
' ' 1.5 0.255 0.382d d
d d
x F x pU pU
x F x pU pU
The relay function setting is calculated as follows.
1.40
' 0.382 1.40.891
2 2 2 2
d
d d
Diameter x pU
x x pU pUCenter pU
The relay will be set to the next possible set point:
Diameter: 1.4 pUCenter: 0.89 pU
The Time Delay Stage 1 is set to 5 sec.
The parameters Operate Value St. 2, Rotor Cur. Comp., Rotor Cur. Offset has no relevance.Stage 2 is using the following logical function:
The Time Delay Stage 2 is set to 1 sec.The Operate Value of the Function "27/50" is set to 50V.
& TripUnderexcitation Stage 1 PickupUndervoltage 27/40 Pickup
Time Delay Stage 2
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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C) GENERATOR NEGATIVE PHASE SEQUENCE PROTECTION 46G
The calculation of the setting values is done according to e.g. following generator data:
Rated power SG =55560 KVARated voltage VG = 11 kVNegative phase sequence current withstand 8%
Therefore the generator primary current is
555602916.14
3 11 3
ggp
gp
S kVAI A
V kV
and by using a current transformer with a CT ratio of 12000A/1A the corresponding secondary current is
2916.14A5 3.64
4000
gpgs
II A A
CTratio A
So the CT ratio compensation is
3.64 0.73
5gs
N
I ACT ratio comp
I A
A further data for the generator (manufacturer data) is the inverse time characteristic i2t, which is for example
i2t=20s
Note: This characteristic is only valid for high current values i, as shown below (calculation tripping time).
So the time constant is selected to be
2
203125 52
0.08
ss min
The tripping time can be calculated exactly
2
222
22ln
e
tripii
it
In case of a failure with n.p.s=45%, i2 results to 5xi2e, and the tripping time is
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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25ln 0.0408 127.5
24tript s
Compared with the manufacturer data
2 22
3.5 2098.7
0.45trips s
t si
The values for the "neg.ph.sequ.alarm" and "neg.ph.sequ.trip" are selected as a percentage of the load limit. The load limit is reached after approximately 4 time constants when running constant admissible unbalance current. Typical values are (depends on the customer wishes):
neg.ph.sequ.alarm=80%neg.ph.sequ.trip=100%
D) GENERATOR OVERVOLTAGE PROTECTION 59
The overvoltage function protects the generator and the transformer against electrical field stresses. The function is provided with 2 stages whereby stage 1 has a lower voltage setting and a larger time delay to cater for voltage regulator response time in case of full load rejections and stage 2 is provided with a higher voltage setting above loss of load conditions and minimum time delay.
The calculation of the setting value for Stage 1 is as follows
The setting is chosen to be 110% of the generator rated voltage, therefore
VV
VV
VTratio
VV
gps 0.12110.1
11000
11011000%110
and the time delay is set to t = 2.0 s
Stage 2 is selected to be 125% of the generator rated voltage, therefore
VV
VV
VTratio
VV
gps 5.13725.1
11000
11011000%125
and the time delay is set to t = 0.0 s
Setting:
Name of parameter Range UnitOperate Value Stage 1 121.0 VOperate Value Stage 2 137.5 VTime Delay Stage 1 2 SecTime Delay Stage 2 0 SecType 1 Over Voltage
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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E) GENERATOR UNDERVOLTAGE PROTECTION 27G
The function is enabled during the generator set being connected to the power system and is disabled (blocked) by the 220kV CB open position. It is a 1-stage function.
The function settings are selected as follows.
VVVV ns 7711070.0%7027 Time delay st 5.227 trip
Setting:
Name of parameter Range UnitOperate Value 77 [V]Time Delay 2,5 [Sec]Type 2 Under Voltage -
F) GENERATOR OVER/UNDERFREQUENCY PROTECTION 81O/U
The protective function has 4 Stages providing separate adjustable over- and under-frequency alarm and trip facilities. In addition to the mechanical overspeed and excitation system underspeed detection it provides backup protection for such conditions. All stages will initiate an alarm and trip the unit.
The function settings are selected as follows.
Stage 1 overfrequency Hzf 0.521.81 time delay st 5.01.81 TripStage 2 overfrequency Hzf 5.522.81 time delay st 0.02.81 TripStage 3 underfrequency Hzf 5.483.81 time delay st 0.203.81 TripStage 4 underfrequency Hzf 0.474.81 time delay st 0.04.81 Trip
The frequency settings need to be reviewed by the grid regulator.
Setting:
Name of parameter Range UnitMin. Volt. Setting 60 100 [V]Max. Volt. Setting 100 140 [V]Operate Value St. 1 52 [Hz] Time Delay St. 1 0.5 [s]Type St. 1 OverdetectionOperate Value St. 2 52.5 [Hz]Time Delay St. 2 0.00 [s]Type St. 2 OverdetectionOperate Value St. 3 48.5 [Hz] Time Delay St. 3 20 [s]Type St. 3 UnderdetectionOperate Value St. 4 47 [Hz]Time Delay St. 4 0.00 [s]Type St. 4 Underdetection
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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G) GENERATOR STATOR EARTH FAULT PROTECTION 64G1
The function should serve as an earth fault function for the complete 11kV-system and for the generator up to 90% of its winding. With an earth fault in the 11kV-system (respectively on the terminals of the generator) we receive the following voltage in the generator neutral:
VVkV
kV
ratiotransf
VV
Gen
N 5.63110/11
1
3
111
3sec
For a protection range of 90% we are able to calculate the setting value:
VVVrangeprot
V Nset 18.35.63%100
%95%100
%100
.%100sec
Selected value (according to setting range of the protection relay): 3.2V.
Time delay 1.0s
Setting:
Name of parameter Range UnitOperate Value 3.2 VTime Delay 1.0 SecType Over detection -
H) GENERATOR STATOR EARTH FAULT PROTECTION 64G2
For simplification an evenly distribution of the 3rd harmonic over neutral and terminals for the generator in healthy condition is assumed (see figure below).
This distribution of the 3rd harmonic over neutral and terminal side is taken for the evaluation of earth faults close to the generator neutral. The 3rd harmonic is measured in the generator neutral with a single-phase voltage transformer and on the generator leads with a voltage transformer in open delta
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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connection. In case of an earth fault, the 3rd harmonic in the neutral is shorted whereby the value on the generator terminals is increased by the same value (see figure below).
The following requirement is assumed: the relay with the measurement of the 3rd harmonic shall protect the 15% of the stator coil close to the neutral point. The other 85% are protected by a normal overvoltage relay with the measurement of the fundamental frequency. The correct settings will be determined on site during earth fault tests. For this purpose different measurements of the 3rd harmonic in the generator neutral and on the generator leads have to be done in dependence of different generator loads for the healthy condition and for an earth fault.
The 3rd harmonics are processed via the following formula:
valuesmeasuredvoltneutralgenHarmrdratiovoltalmintergenHarmrd ....3....3There should be a difference between the measured values for the healthy condition and for the case of an earth fault.
Setting:
Settings will be determined on site during earth fault tests.
I) ROTOR EARTH FAULT PROTECTION 64R
This protection function comprises an auxiliary supply, which is connected between the earth and one side of the field circuit. A direct voltage appears at the output, which is indirectly proportional to the rotor insulation value and corresponds to the resistance. If this measured resistance is smaller than the setting value, the required trip sequences for a unit shutdown are carried out.
The setting of the rotor earth fault protection is selected to
Stage 1: kR 50 with a time delay stdelay 10
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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Stage 1 will initiate an Alarm only.
Stage 2: 1500R with a time delay stdelay 1Stage 2 will initiate a trip.
Setting:
Name of parameter Setting UnitOperate Value, Stage1 50 [k]Time Delay, Stage1 10 [s]Operate Value, Stage2 1.5 [k]Time Delay, Stage2 1 [s]
J) GENERATOR REVERSE POWER PROTECTION 32G
When operating on reverse power this protective function will perform a unit shut down. The setting is selected due to our experience, i.e. -5.0% of the generator rating power.
The relay function setting is calculated as follows.
The relay primary power is
kWAkVIVP CTpprelp 77.5715130000.113cos3
The required -5.0% primary reverse power setting of the machine rating is
kWAkVIVP gpp 2259.04.26200.11305.0cos3%0.532
The required relay setting is Pp32/Prelp = -225/5715.77 = -3.94%
The time delay is set to st 0.532
Setting:
Name of parameter
Setting Unit
Operate Value -3.94 [% PN]Time Delay 5 [s]Power Direction Direction 1 -Phase Rotation Right -
K) VOLTAGE SUPERVISION FUNCTION 60G, 60M AND 60A
The setting for the negative phase sequence voltage for unbalanced secondary phase to phase voltages is selected to
Operate Value U=50.0 V with a time delay t=5s
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The second condition of the function is the setting for the negative phase sequence current. A high negative phase sequence current indicates e.g. a failure in the network and the protection function is blocked. Normally an unbalanced voltage causes only a small n.p.s. current. So the setting is chosen to be
Operate Value I=0.2 A
The selection parameter declares the setting for the phase rotation.
Setting:
Name of parameter Range UnitOperate Value I 0.2 AOperate Value U 50 VTime Delay 5 [s]Phase Rotation 2 (Right) -
L) GENERATOR UNDERIMPEDANCE PROTECTION 21G
This protection function consists of two stages, whereby the first stage is a so called impedance protection relay with a current interlock and the second stage is a backup protection, which is designed as overcurrent protection relay.
Therefore the generator current is
AV
SI
gp
ggp 4.262
3
Generator primary current
The current and voltage transformer are designed according to the related voltage and rated current of the generator. For this purpose the VT ratio is selected to be 11000V/110V and the CT ratio of the current transformer at the neutral is selected to be 10000/1A
The HV and LV transformer currents are:
AV
SI
hvp
thvp 73.57
3
HV transformer primary current
AV
SI
Lvp
tLvp 35.577
3
LV transformer primary current
The primary short circuit impedance of the transformer is obtained by
835.0
10011
50.711
100
22
MVAVku
SVZ
k
t
TSp
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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Therefore the secondary transformer impedance is calculated
495.0825.0
110005
110300ps Z
VTratio
CTratioZ
In order not to overreach on external system faults an impedance of approximately 50% to 70% of the transformer is selected with a corresponding setting of
247.073.15.0%5021 sG ZZ With time delay st G 2.021
The impedance current interlock setting, i.e. the overcurrent stage is a starting element for the under impedance stage, is set to 120% of the generator rated current and calculated as follows
AratioCT
IIs LV 55.11300
535.5772.1
12.1
The time delay setting for stage 2 depends on the time grading of the remaining network.
Setting:
Name of parameter
Range Unit
Operate Value 0.25 [Ohm]Time Delay Imp. 0.2 [s]Time Delay Curr. Depends on time grading of remaining n/w [s]Current Interlock 11.55 A
M) DEAD MACHINE 27/51V
The overcurrent setting will be coordinated with all the other overcurrent functions (generator, transformer ...).
AI V 10.151/27 The typical operating range of a generator lies between 90% and 110% of the rated voltage. For generators with an isolated starpoint or with an earthed starpoint via a resistor the generator voltage drops to values of about 30% caused of a phase to phase fault. For this case the parameter "Voltage Limit" has to be chosen in that way, that the generator voltage is below the setting of this parameter. The operating value of the current setting will then be reduced to the "K-Factor". The setting is chosen to be 60% of the generator nominal voltage; this is for the secondary side:
VV V 0.66110%100
%6051/27
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The k-factor is chosen to be 20% (to make sure that the current exceeds the setting value).
2.0K
Setting:
Name of parameter Range UnitOperate Value 1.1 [A]Voltage Limit 66 [V]K-Factor 0.2 -Time Delay 4 [s]
N) UNIT DIFFERENTIAL PROTECTION 87GT
The unit differential protection is protecting the system from the transformer 220kV CTs up to the 11kV generator neutral and Auxiliary Transformer busbar CTs. When operating the unit is tripped and will be shut down immediately.
AkV
kVA
V
SI
hvp
thvp 74.57
3110
11000
3
HV transformer primary current
AAA
A
CTratio
II
hvphvs 96.00.1
60
74.57 HV transformer secondary current
With a differential current setting of 0.20xIn the setting as a percentage of the transformer rated current can be calculated
%8.2010096.0
20.0%
A
A
I
II
hvs
shvs
By choosing a differential current setting of 0.20A secondary the primary setting is calculated as follows.
AAA
AIratioCTI hvshvp 7515.0
0.1
500
High set over current = 5.0 x IN =4.8
To cater for the different CT ratios on the transformer HV and LV side the CT ratio compensation factor system2/system1 and systm3/system1 is calculated according to following formulas whereby system 1 refers to the 220kV HV winding, system 2 to the generator leg and system 3 to the aux transformer LV winding.
5
5.0
11
1101/60
1/300
2
1.1
212
kV
kVA
A
system
systemratiotrCTsystem
CTsystemcompCTratio
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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05.0
11
1101/60
1/300
3
1.1
313
kV
kVA
A
system
systemratiotrCTsystem
CTsystemcompCTratio
Setting:
Name of parameter Range UnitOperate Value 20% -High Set OC 4,8A -CT Ratio Comp. 2-1 0.5 -CT Ratio Comp. 3-1 0.05 -2nd Harmonic 20 (to be verified during commissioning) %5th Harmonic 15 (to be verified during commissioning) %Bias 50 %Vector Group 1-2 1 -Vector Group 1-3 11 -Zero Sequ. Syst.1 On -Zero Sequ. Syst.2 Off -Zero Sequ. Syst.3 Off -
O) RESTRICTED EARTH FAULT PROTECTION 64REF
The grid transformer restricted earth fault protection 64REF is protecting the system from the transformer 220kV CTs up to the grid transformer neutral to cater for faults near the neutral point (grid transformer). High impedance scheme and high speed tripping is provided. When operating the function trips the generator unit.
CT data for the 220kV transformer feeder switchgear CTs.
CT ratio 600/1,0 ACT secondary current In = 1,0 A Estimated CT knee point voltage Vk > 300 VEstimated CT secondary resistance Rct = 5 Estimated single lead resistance to relay Rl = 0.3
CT data for the 220kV transformer neutral CT
CT ratio 600/1,0 ACT secondary current In = 1,0 A Estimated CT knee point voltage Vk > 300 VEstimated CT secondary resistance Rct = 5 Estimated single lead resistance to relay Rl = 0.3
The CT requirements for the High impedance transformer restricted earth fault protective function, is according to the following formula.
Vk > 2IF ( Rct + 2 Rl + Rext )
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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Whereby IF is the maximum secondary three phase through fault current considering a short circuit failure. The secondary fault current IF at the 220kV level is calculated as follows (British EATS 48-3 standard).
AAkV
kVA
CTratioV
SI
TF 24.12
0.1/6002203
17500016
316
220kV lead CTs Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V220kV neutral CT Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V
Therefore the selected restricted earth fault protection voltage setting is chosen to be greater than the minimum stability voltage IFx( Rct + 2 Rl + Rext )=68.58V Vs=69V and the resulting external stabilising resistor for a relay setting IS = 0.15A (33% rated current) is
45515.0
15.0
1.069
S
SS
STI
I
relayVAV
R
The minimum CT kneepoint voltage should be greater than twice the relay voltage setting
220kV: Vk = 300V > 2 x VS = 138V
Check, whether a voltage limiting device is required:
VVVVV KfKp 3000 22 VK=300V
VRRRRIV RSTlCTFf 56374553.02524.122
Thus, VVp 3579
Due to ensure a safety margin a voltage limiting resistor is connected into the circuit.
Continuous power rating of the setting resistor:
WRIP STScon 2.1045515.0 22 with a short time rating:
ondsforW
R
IRV
R
VP
ST
FSTK
ST
fsshort sec5.0 159
3.12
4
13
2
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Thermal rating of the non-linear resistor:
WVAVIP KF 94.467730024.1215.3
44
AR
VI
STsetting 15.0
455
69
Settings:
Name of parameter Range UnitOperate Value 42.5 % -Drop Off Delay 0.5 s
P) RESTRICTED EARTH FAULT PROTECTION 64REF- DISCRETE RELAY
The grid transformer restricted earth fault protection 64REF is protecting the system from the transformer 220kV CTs up to the grid transformer neutral to cater for faults near the neutral point (grid transformer). High impedance scheme and high speed tripping is provided. When operating the function trips the generator unit.
CT data for the 220kV transformer feeder switchgear CTs.
CT ratio 600/1,0 ACT secondary current In = 1,0 A Estimated CT knee point voltage Vk > 300 VEstimated CT secondary resistance Rct = 5 Estimated single lead resistance to relay Rl = 0.3
CT data for the 220kV transformer neutral CT
CT ratio 600/1,0 ACT secondary current In = 1,0 A Estimated CT knee point voltage Vk > 300 VEstimated CT secondary resistance Rct = 5 Estimated single lead resistance to relay Rl = 0.3
The CT requirements for the High impedance transformer restricted earth fault protective function, is according to the following formula.
Vk > 2IF ( Rct + 2 Rl + Rext )
Whereby IF is the maximum secondary three phase through fault current considering a short circuit failure. The secondary fault current IF at the 220kV level is calculated as follows (British EATS 48-3 standard).
AAkV
kVA
CTratioV
SI
TF 24.12
0.1/6002203
17500016
316
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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220kV lead CTs Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V220kV neutral CT Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V
Therefore the selected restricted earth fault protection voltage setting is chosen to be greater than the minimum stability voltage IFx( Rct + 2 Rl + Rext )=68.58V Vs=69V and the resulting external stabilising resistor for a relay setting IS = 0.15A (33% rated current) is
22.16215.0
15.01.0
69
S
SS
STI
IrelayVA
VR
The minimum CT kneepoint voltage should be greater than twice the relay voltage setting
220kV: Vk = 300V > 2 x VS = 138V
Check, whether a voltage limiting device is required:
VVVVV KfKp 3000 22 VK=300V
28.205522.1623.02524.122 RSTlCTFf RRRRIV
Thus, VVp 48.2052
Due to ensure a safety margin a voltage limiting resistor is connected into the circuit.
Continuous power rating of the setting resistor:
WRIP STScon 65.322.16215.0 22 with a short time rating:
onds for W
R
IRV
R
VP
ST
FSTK
ST
fsshort sec5.082.2412
3.12
4
13
2
Thermal rating of the non-linear resistor:
WVAVIP KF 94.467730024.1215.3
44
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
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AR
VI
STsetting 42.0
22.162
69
Settings:
Name of parameter Range UnitOperate Value 42.5 % -Drop Off Delay 0.5 s
Q) OVERFLUXING PROTECTION 99G
The degree of saturation (overfluxing) is calculated according to following formula.
fV
fVS
N
N
Whereby V and VN are the actual voltage and rated voltage and f and fN the actual frequency and rated frequency respectively.
The operating value of stage 1 is set to the maximum continuous overfluxing withstand of the generator, which must be specified by the manufacturer of the generator, i.e. to 105% voltage at rated frequency and the other stage is set to increasing higher levels.
Stage 1 alarm S1A=1.05 time delay t=10.0sStage 2 trip S2T=1.10 time delay t=1.0s
Setting:
Name of parameter Setting UnitOperate Value St. 1 1.05 [p.U.]Time Delay St. 1 10.00 [s]Operate Value St. 2 1.10 [p.U.]Time Delay St. 2 1.00 [s]Nominal Frequency 50.0 [Hz]Nominal Voltage 110 [V]
R) UAT DIFFERENTIAL PROTECTION 87UAT
This function protects the UAT system from the HV side CTs to the LV side CTs and operates for phase to phase and three phase faults.
The differential setting value is calculated as follows:
AkV
kVA
V
SI
np
ATAT-HVp 24.26
311
500
3
UAT (HV) primary current
Now with a CT ratio = 30/5 A the generator secondary current is calculated
AAA
A
CTratio
II
AT-HVpAT-HVs 37.45
30
24.26 UAT (HV) secondary current
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AV
kVA
V
SI
np
ATAT-LVp 60.695
3415
500
3
UAT (LV) primary current
and with a CT ratio of 800/5A the corresponding secondary current is
AAA
A
CTratio
II
AT-LVpAT-LVs 87.01
800
60.695 UAT (LV) secondary current
The differential current setting is chosen to be 20% of the relay current rating, i.e.
AAI s 00.1520.087
This is in turn the equivalent to the generator rated current.
%16.3810062.2
0.1100%
A
A
I
II
AT-HVs
s
High set overcurrent = 5.0 x IN =13.1
The bias slope is set to %40bias
00.1
415.0
111/30
800
2
1.1
2
kV
kVA
system
systemratiotrCTsystem
CTsystemcompCTratio
Setting:
Name of parameter Range UnitOperate Value 38.16% -High Set OC 13.1 -CT Ratio Comp. 2-1 1.00 -2nd Harmonic 20 (to be verified during commissioning) %5th Harmonic 15 (to be verified during commissioning) %Bias 40 %Vector Group 1-2 11 -Zero Sequ. Syst.1 Off -Zero Sequ. Syst.2 Off -
S) UAT OVERCURRENT PROTECTION 50U/51U
This function protects the auxiliary transformer against substantial overloading and heavy internal and external HV side short circuits and will trip the generator unit when operating. For the overcurrent protection stage 1 an inverse time characteristic is chosen to cater for field forcing conditions and the current setting is selected to be 1.0x the transformer rated current. The overcurrent protection stage 2 setting is chosen to be about 5 x In with a small time delay
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT
MALANA-II HEP Page 23 of 29
The protective function settings are obtained
AkV
kVA
V
SI
np
ATATp 24.26
311
500
3
auxiliary transformer primary current
and with a CT ratio of 50/5A the corresponding secondary current is
AAA
A
CTratio
II
ATpATs 62.25
50
24.26 auxiliary transformer secondary current
Hence the current setting for Stage 1 is selected to be 120% of the rated current
AAII ATs 15.32.162.22.151
With a Time Multiplier setting 5.0TMS normally inverse time characteristic
The Stage 2 current setting is selected to be approximately 5 x In and is obtained
AAII 75.150.515.30.55150
The time delay of Stage 2 is chosen to be st 1.050
Setting:
Name of parameter Range UnitOperating Val. St.1 3.15 ATMS St.1 0.5 -Curve normal inverse -Operating Val. St.2 15.75 ATime delay St.2 0.1 Sec
4. Distance Protection
Line Parameters:
POSITIVE SEQUENCE RESISTANCE R1 0.0659 OHMS/KMPOSITIVE SEQUENCE REACTANCE X1 0.3836 OHMS/KMZERO SEQUENCE RESISTANCE R0 0.272 OHMS/KMZERO SEQUENCE RESISTANCE X0 1.233 OHMS/KMLINE LENGTH L1 70 KMLENGTH OF NEXT SHORTEST LINE L2 30 KMLENGTH OF NEXT LONGEST LINE L3 30 KMARC RESISTANCE PH-PH Arc ph-ph 0 OHMSARC RESISTANCE PH-EARTH Arc ph-e 20 OHMS
Primary Values per Km:
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT
MALANA-II HEP Page 24 of 29
R1=0.0659X1=0.3836R0=0.272X0=1.233
3892.0111 22 XRZ
2517.801
11),( 1
R
XTanPhPhLineAngle
2626.1000 22 XRZ
5598.770
00),( 1
R
XTanEPhLineAngle
Values Protected Line:
Primary Value:
R1pL1=0.0659*70=4.6130X1pL1=0.3836*70=26.8508R0pL1=0.2720*70=19.0400X0pL1=1.2330*70=86.3100
Secondary Value:
06.0PTratio
CTratio
R1sL1=4.6130*0.06=0.2767X1sL1=26.8508*0.06=1.6110R0sL1=19.0400*0.06=1.1424X0sL1=86.3100*0.06=5.1786
Earth Impedance (residual) Compensation:
Resistance Ratio:
Reactance Ratio:
Earth Compensation Factor, Ko:
04248.113
1
1
0
R
R
R
R
L
G
7381.013
1
1
0
X
X
X
X
L
G
1
3
1
1
00 Z
ZK
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT
MALANA-II HEP Page 25 of 29
iK 0508.07469.00 7486.00508.07469.0)( 220 KABS
89.37469.0
0508.0tan)( 10 KARG
Next Shortest Line:
Primary Value:
R1pL2=0.0659*30= 1.9770X1pL2=0.3836*30= 11.5075R0pL2=0.2720*30= 8.1600X0pL2=1.2330*30= 36.99
Secondary Values:
R1sL2=1.9770*0.06=0.1186X1sL2=11.5075*0.06=0.6904R0sL2=8.1600*0.06=0.4896X0sL2=36.9900*0.06=2.2194
Next Longest Line:
Primary Value:
R1pL3=0.0659*30= 1.9770X1pL3=0.3836*30= 11.5075R0pL3=0.2720*30= 8.1600X0pL3=1.2330*30= 36.99
Secondary Values:
R1sL3=1.9770*0.06=0.1186X1sL3=11.5075*0.06=0.6904R0sL3=8.1600*0.06=0.4896X0sL3=36.9900*0.06=2.2194
KPCL Setting Philosophy:
Zone1 : 80% of Protected Line
Zone2 : 100% of protected line + 50% of next shortest line
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT
MALANA-II HEP Page 26 of 29
Zone3 : 100% + 100% of next longest line
Zone4 : Normally 15% to 20% of Zone 1
Zone 1 Calculation:
Phase to Phase Faults:
Primary Values
69.3)8.0*11(11 pharcphpLRpZR 481.21)8.0*11(11 pLXpZX
Secondary Values
221.006.0*1111 pZRsZR 289.106.0*1111 pZXsZX
Phase to Earth Faults:
Primary Values
232.35)8.0*10(10 earcphpLRpZR 048.69)8.0*10(10 pLXpZX
Secondary Values
114.206.0*1010 pZRsZR 143.406.0*1010 pZXsZX
Zone 2 Calculation:
Phase to Phase Faults:
Primary Values
602.5)5.0*21()11(21 pharcphpLRpLRpZR 605.32)5.0*21()11(21 pLXpLXpZX
Secondary Values
336.006.0*2121 pZRsZR 956.106.0*2121 pZXsZX
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT
MALANA-II HEP Page 27 of 29
Phase to Earth Faults:
Primary Values
120.43)5.0*20()10(20 earcphpLRpLRpZR 805.104)5.0*20()10(20 pLXpLXpZX
Secondary Values
587.206.0*2020 pZRsZR 288.606.0*2020 pZXsZX
Zone 3 Calculation:
Phase to Phase Faults:
Primary Values
590.6)31()11(31 pharcphpLRpLRpZR 358.38)31()11(31 pLXpLXpZX
Secondary Values
395.006.0*3131 pZRsZR 301.206.0*3131 pZXsZX
Phase to Earth Faults:
Primary Values
200.47)30()10(30 earcphpLRpLRpZR 300.123)30()10(30 pLXpLXpZX
Secondary Values
832.206.0*3030 pZRsZR 398.706.0*3030 pZXsZX
Reverse Zone 4 Calculation:
Phase to Phase Faults:
Primary Values
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT
MALANA-II HEP Page 28 of 29
923.0)2.0*11(41 pharcphpLRpZR 370.5)2.0*11(41 pLXpZX
Secondary Values
055.006.0*4141 pZRsZR 322.006.0*4141 pZXsZX
Phase to Earth Faults:
Primary Values
808.23)2.0*10(40 earcphpLRpZR 262.17)2.0*10(40 pLXpZX
Secondary Values
428.106.0*4040 pZRsZR 036.106.0*4040 pZXsZX
Settings:
Name of parameter Set Value Unit
Line Angle ph-ph 80.2517 Degreesph-e 77.5598
Earth fault Compensation Factors
Re/Rl 1.042489Xe/Xl 0.738143
Zone 1(Forward)
ph-ph R 0.221
OhmsX 1.289
ph-eR 2.114X 4.143
Zone 2(Forward) ph-ph
R 0.336 OhmsX 1.956
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SETTING CALCULATION NUMERICAL PROTECTION SYSTEM
2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT
MALANA-II HEP Page 29 of 29
ph-e R 2.587X 6.288
Zone 3(Forward)
ph-ph R 0.395
OhmsX 2.301
ph-e R 2.832X 7.398
Zone 4(Reverse)
ph-ph R 0.055
OhmsX 0.322
ph-eR 1.428X 1.036
Operation time
Zone 1 0
secsZone 2 0.4Zone 3 0.8Zone 4 1.2