Settings Example - GE L60 Instruction Manual

10 APPLICATION OF SETTINGS
87PC TRANS BLOCK RESET:
This setting is used to reset transient blocking and allow tripping. According to local conditions, setting should be consid-
ered as the sum of protection operating time and breaker opening time of the adjacent line and minus the Transient Pickup
value to override uncertainty during clearing external faults. The faster the fault clearing at the adjacent line, the lower set-
ting could be applied.
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.
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 2000 A, CT ratio 2000/5, minimum expected internal three-phase fault is
8000 A.
1. Mixed signal factor K = 0.2
2. FDL pickup: I = 1.1 × 2000 × 0.2 = 440 A or 440 / 400 = 1.1 A secondary.
FDL
The setting is 1.1 / 5 = 0.22 pu.
3. FDH pickup: I = 4/3 × I
FDH
setting is 1.76 / 5 = 0.31 pu. Where I
4. Stability angle:
φload = 2 × arcsin((2000 × 50 × √3) / (2 × 765000)) = 13.0°
φcapac = arctan(I
capac
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. When minimum internal three-phase fault current is at
least twice the maximum line load current, no distance element is required to be assigned to the
this example, the minimum internal three-phase fault is much more than twice the maximum line load current, so no
distance element is assigned to the
GE Multilin
765 kV
L60-1
100 miles
2000/5
Figure 10–1: SETTINGS EXAMPLE
+ 0.375 × I = 1.33 × 440 + 0.375 × 80 = 615.2 A or 615.2 / 400 = 1.54 A secondary;
FDL capac
= 765000/(√3 × 5520) = 80 A
capac
/ I ) = arctan(80 / 615.2) = 7.4°
FDH
setting.
FD INPUT
L60 Line Phase Comparison System
10.1 PHASE COMPARISON ELEMENT 87PC

10.1.3 SETTINGS EXAMPLE

L60-2
2000/5
831813A1.CDR
setting. In
FD INPUT
10
10-3