Settings Example - GE L60 Instruction Manual

9 APPLICATION OF SETTINGS
Ttr_rst = Tprot_adj + Tbreak_adj – Ttr_pkp
where: Tprot_adj is the expected time of main protection operation on the adjacent line,
Tbreak_adj is the operation time of the breaker on the adjacent line,
Ttr_pkp is selected Transient Pickup time.
87PC BLOCK:
The user can define some cases when blocking of the phase comparison scheme is required. This setting will block the trip-
ping function. PLC alarm contacts indicating channel failure are usually assigned for this setting,. especially in blocking
schemes.
87PC CHNL LOSS TRIP WINDOW:
This setting is applicable to the 2TL-BL-DPC-2FL scheme only. The typical setting is 150 ms.
765 kV
L60-1
∼
2000/5
Consider settings for a single-circuit 765 kV line, 100 miles length, 50 Ohms primary impedance, 5520 ohms shunt capaci-
tance of the line, maximum expected load of 2000A, CT ratio 2000/5, minimum expected internal 3-phase fault is 8000A.
1. Mixed signal factor K=0.2
= 1.1 × 2000 × 0.2 = 440 A or 440 / 400 = 1.1 A secondary.
2. FDL pickup: I
FDL
The setting is 1.1 / 5 = 0.22 pu.
3. FDH pickup: I = 4/3*I
FDH FDL
1.76/5 = 0.31 pu. Where Icapac=765000/(√ 3*5520) = 80 A
4. Stability angle:
φload = 2*arcsin((2000*50*√ 3)/(2*765000)) = 13.0°
φcapac = arctan(Icapac/I
φs(deg) = 13.0°+7.4°+10° = 30.4°
Minimum recommended setting 60° (set as default) should be applied.
5. Check against requirement for trip supervision by distance relay: As minimum internal 3-phase fault is much than twice
the maximum line load current, no distance element is required for be assigned to FD INPUT setting.
GE Multilin
100 mi
+0.375*Icapac = 1.33*440+0.375*80 = 615.2 A or 615.2/400 = 1.54 A secondary; setting is
) = arctan(80/615.2) = 7.4°
FDH
L60 Line Phase Comparison Relay
9.1 PHASE COMPARISON ELEMENT 87PC

9.1.3 SETTINGS EXAMPLE

L60-2
∼
2000/5
9
9-3