A)Line parameters
1)Rated line voltage - 400 kV
3)Max power flow in the line - 7109.02 MVA 4)Positive sequence resistance - 0.029792 ohms/km 5)Positive sequence reactance - 0.332 ohms/km 6)Zero sequence resistance - 0.16192 ohms/km 7)Zero sequence reactance - 1.24 ohms/km B)CT/PT details
1)CT primary rating - 1000A
2)CT secondary rating - 6A
3)PT primary rating - 400000 V 4)PT secondary rating - 110 V
C)Source Impedance
1)Fault MVA at local end - 1694.61MVA
2)Fault MVA at remote end - 1694.61 MVA(assumed) 3)Source impedance angle - 80º (assumed)
E)Fault resistance
1)Fault resistance in primary for phase-earth faults - 20 ohms 2)Fault resistance in primary for phase-phase faults - 5 ohms
Relay details:-
In=1A,Un=110VCalculations :-
Impedance ratio = CTR/PTR = (1000/6) /(400000/110) = 0.045833Positive sequence line resistance in secondary,R1 = 0.029792 x 189 x 0.045833
= 0.2580 ohms
Positive sequence line reactance in secondary,X1 = 0.332 x 189 x 0.045833 = 2.8759 ohms
Zero sequence line resistance in secondary,R0 = 0.16192 x 189 x 0.045833
= 1.4026 ohms
Zero sequence line reactance in secondary,X0 = 1.24 x 189 x 0.045833
= 10.7414 ohms
Fault resistance in secondary for phase-earth faults , Rfe = 20 x 0.045833
= 0.9167 ohms
Fault resistance in secondary for phase-phase faults , Rfp = 5 x 0.045833
= 0.2291 ohms
Zone-1 is set to protect 80% of the line Zone-2 is set to protect (120% of the line) Zone-3 is set to protect (200% of the line)
Zone-1 setting
Positive sequence resistance , R1PP&R1PE = 0.8 x 0.2580
= 0.2064 ohms/phase
Positive sequence reactance , X1PP&X1PE = 0.8 x 2.8759
= 2.3007 ohms/phase
Zero sequence resistance , R0PE = 0.8 x 1.4026
= 1.1221 ohms/phase
Zero sequence reactance , X0PE = 0.8 x 10.7414 = 8.5931 ohms/phase Resistive reach for phase-phase faults,
RFPP = 2 x Min { Max (Fault resistance, X tan 25 +R) , 3X }
= 2 x Min { Max (Rfp , X1PP tan 25 +R1PP) , 3X1PP }
= 2 x Min { Max (0.2291, 2.3007 x 0.4663 + 0.2064) , 3 x 2.3007} = 2 x Min {1.2792, 6.9021 }
= 2.5584 ohms / loop Resistive reach for phase-earth,
RFPE = Min { Max (Fault resistance, X tan 25 +R) , 4.5X }
= Min { Max (Rfe , X1PE tan 25 +R1PE) , 4.5X1PE }
= Min { Max (0.9167 , 2.3007 x 0.4663 +0.2064) , 4.5 x 2.3007} = Min { 1.2792 , 10.3532 }
= 1.2792 ohms / loop Zone-2 setting
Positive sequence resistance , R1PP&R1PE = 1.2 x 0.2580
= 0.3096 ohms/phase
Positive sequence reactance , X1PP&X1PE = 1.2 x 2.8759
= 3.4511 ohms/phase
Zero sequence resistance , R0PE = 1.2 x 1.4026
= 1.6831 ohms/phase
Zero sequence reactance , X0PE = 1.2 x 10.7414
= 12.8897 ohms/phase
Resistive reach for phase-phase faults,
RFPP = 2 x Min { Max (Fault resistance, X tan 25 +R) , 3X }
= 2 x Min { Max (Rfp , X1PP tan 25 +R1PP) , 3X1PP }
= 2 x Min { Max (0.2291 , 3.4511 x 0.4663 + 0.3096) , 3 x 3.4511} = 2 x Min { 1.9188, 10.3533 }
= 3.8376 ohms / loop Resistive reach for phase-earth,
RFPE = Min { Max (Fault resistance, X tan 25 +R) , 4.5X }
= Min { Max (Rfe , X1PE tan 25 +R1PE) , 4.5X1PE }
= Min { Max (0.9167 , 3.4511 x 0.4663 + 0.3096) , 4.5 x 3.4511} = Min { 1.9188 , 15.5299 }
= 1.9188 ohms/ loop Zone-3 setting
= 0.516 ohms/phase Positive sequence reactance , X1PP&X1PE = 2 x 2.8759
= 5.7518 ohms/phase
Zero sequence resistance , R0PE = 2 x 1.4026
= 2.8052 ohms/phase
Zero sequence reactance , X0PE = 2 x 10.7414
= 21.4828 ohms/phase
Resistive reach for phase-phase faults,
RFPP = 2 x Min { Max (Fault resistance, X tan 25 +R) , 3X }
= 2 x Min { Max (Rfp , X1PP tan 25 +R1PP) , 3X1PP }
= 2 x Min { Max (0.2291 , 5.7518 x 0.4663 + 0.516) , 3 x 5.7518} = 2 x Min { 3.1981 , 17.2554 }
= 6.3962 ohms / loop Resistive reach for phase-earth,
RFPE = Min { Max (Fault resistance, X tan 25 +R) , 4.5X }
= Min { Max (Rfe , X1PE tan 25 +R1PE) , 4.5X1PE }
= Min { Max (0.9167 , 5.7518 x 0.4663 + 0.516) , 4.5 x 5.7518} = Min { 3.1981, 25.8831 }
= 3.1981 ohms / loop Zone-4 setting (reverse)
Positive sequence resistance , R1PP&R1PE = 0.2 x 0.2580
= 0.0516 ohms/phase
Positive sequence reactance , X1PP&X1PE = 0.2 x 2.8759
= 0.5752ohms/phase
Zero sequence resistance , R0PE = 0.2 x 1.4026
= 0.2805ohms/phase
Zero sequence reactance , X0PE = 0.2 x 10.7414
= 2.1483 ohms/phase
Resistive reach for phase-phase faults,
RFPP = 2 x Min { Max (Fault resistance, X tan 25 +R) , 3X }
= 2 x Min { Max (Rfp , X1PP tan 25 +R1PP) , 3X1PP }
= 2 x Min { Max (0.2291 , 0.5752 x 0.4663 + 0.0516) , 3 x 0.5752} = 2 x Min { 0.3198 , 1.7256}
= 0.6396 ohms / loop Resistive reach for phase-earth,
RFPE = Min { Max (Fault resistance, X tan 25 +R) , 4.5X }
= Min { Max (Rfe , X1PE tan 25 +R1PE) , 4.5X1PE }
= Min { Max (0.9167 , 0.5752 x 0.4663 + 0.0516) , 4.5 x 0.5752 = Min { 0.9167 , 2.5884 }
= 0.9167 ohms / loop General Fault Criteria (GFC)
GFC is an overall impedance-measuring element with a very high reach and long time delay for its tripping function. The GFC characteristics should in general cover all the impedance measuring zones used for distance protection ,regardless of their directionality. Normally set to 2 times of zone-3 with a limit on the resistive direction so that the characteristics does not enter the load area.
Positive sequence reactance for ph-ph & ph-e elements in the forward direction ,X1FwPP & X1FwPE = 2 x X3 =2 x 5.7518= 11.5036 ohms/ phase
Positive sequence reactance for ph-ph & ph-e elements in the reverse direction ,X1RvPP & X1RvPE = 2 x X4 =2 x 0.5752 = 1. 1504 ohms/ phase
Positive sequence resistance for ph-ph faults for forward & reverse reach , RFPP = (2[2*R3 + RFPP])
= (2 [2 x 0.516 + 6.3962]) = 14. 8564 ohms/loop
Positive sequence resistance for ph-e faults for forward & reverse reach , RFPE = (2[1/3(2R3 + R03)+RFPE])
= (2[1/3(2 x 0.516+ 2.8052) + 3.1981]) = 8.9541 ohms/loop
Zero sequence reactance for ph-e elements in the forward & reverse direction, X0FwPE & X0RvPE = 2 x X03
= 2 x X0PE
= 2 x 21.4828=42.9656 ohms/phase
The resistive reach in the load impedance area , RLd = Max(RFPP,RFPE) = Max (6.3962,3.1981) = 6.3962 ohms/loop Load Angle, ARGLd = 25º (Assumed)
Power Swing Block Function
The reach of the inner characteristic in the resistive and reactive direction is set so that the inner characteristics covers completely all the distance protection zones,which are to be blocked by the PSD function.At least 10% of additional safety margin is considered.
Reactive reach of the inner characteristics of the power swing blocking element , X1IN = 1.1 x X3
= 1.1 x X1PP
= 1.1 x 5.7518 = 6.3270 ohms/phase
Resistive reach of the inner characteristics of the power swing blocking element , R1IN = 1.1 (2R3 +RFPP)
= 1.1 (2 x 0.516 + 6.3962) = 8.168 ohms/phase
Reach multiplication for the outer reactive boundary, KX = 125%(recommended) Reach multiplication for the outer reactive boundary, KR = 125%(recommended) Setting Recommendations:- 1) Zone-1:- R1PP & R1PE = 0.2064 X1PP & X1PE = 2.3007 R0PE = 1.1221 X0PE = 8.5931 RFPP = 2.5584 RFPE = 1.2792
2) Zone-2 :- R1PP & R1PE = 0.3096 X1PP & X1PE = 3.4511 R0PE = 1.6831 X0PE = 12.8897 RFPP = 3.8376 RFPE = 1.9188
t2PP & t2PE = 0.400 s (time delay for trip) 3) Zone-3 :- R1PP & R1PE = 0.516 X1PP & X1PE = 5.7518 R0PE = 2.8052 X0PE = 21.4828 RFPP = 6.3962 RFPE = 3.1981
t3PP & t3PE = 0.800 s(time delay for trip) 4) Zone-4:- (reverse) R1PP & R1PE = 0.0516 X1PP & X1PE = 0.5752 R0PE = 0.2805 X0PE = 2.1483 RFPP = 0.6396 RFPE = 0.9167
t4PP & t4PE = 0.250 s (time delay for trip) 5) GFC :-
X1FwPP & X1FwPE = 11.5036 X1RvPP & X1RvPE = 1.1504
RFPP = 14.8564
RFPE = 8.9541
X0FwPE & X0RvPE = 42.9656
RLd = 6.3962
ARGLd = 25º
tPP & tPE = 2s(time delay for trip) 6) PSB :-
X1IN = 6.3270
R1IN = 8.168
KX = 125
RX = 125
tP1 = 0.045s(Initial PSD timer for the first swing)
tP2 = 0.015s(Fast PSD timer for the consecutive swings within tW) tW = 0.250s(Hold timer for the activation of fast PSD timer) tH = 0.5s (Hold Timer for PSD detected)
tEF = 60s(Timer overcoming 1-Ph reclosing dead time)
tR2 = 2.00s (On delay timer for blocking of output signal at very slow swings
The time delays tP1,tP2,tW,tH,tEF,tR1,tR2 are recommendations and the same need to be set in accordance with the system studies.
5(b)