GE Multilin L60 Line Phase Comparison Relay 9-39 APPLICATION OF SETTINGS 9.1 PHASE COMPARISON ELEMENT 87PC9Ttr_rst = Tprot_adj + Tbreak_adj – Ttr_pkpwhere: 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 blockingschemes.87PC CHNL LOSS TRIP WINDOW:This setting is applicable to the 2TL-BL-DPC-2FL scheme only. The typical setting is 150 ms.9.1.3 SETTINGS EXAMPLEConsider 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=0.22. FDL pickup: IFDL = 1.1 × 2000 × 0.2 = 440 A or 440 / 400 = 1.1 A secondary.The setting is 1.1 / 5 = 0.22 pu.3. FDH pickup: I FDH = 4/3*I FDL+0.375*Icapac = 1.33*440+0.375*80 = 615.2 A or 615.2/400 = 1.54 A secondary; setting is1.76/5 = 0.31 pu. Where Icapac=765000/(√ 3*5520) = 80 A4. Stability angle:φload = 2*arcsin((2000*50*√ 3)/(2*765000)) = 13.0°φcapac = arctan(Icapac/I FDH ) = arctan(80/615.2) = 7.4°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 twicethe maximum line load current, no distance element is required for be assigned to FD INPUT setting.2000/5L60-1 L60-2765 kV2000/5100 mi∼ ∼
