GE L60, Instruction Manual, Page: 377 / 498

GE Multilin L60 Line Phase Comparison Relay 9-9
9 APPLICATION OF SETTINGS 9.2 DISTANCE BACKUP/SUPERVISION
9
9.2.9 SECURITY ON WEAK OR NOISY PLC CHANNELS
On some 87PC blocking applications, PLC channels can exhibit sudden interruptions in the received blocking signals
(“holes” in the carrier) due to communications noise caused by arcing on the line, leading to 87PC nuisance trip. Extra
security can be achieved by allowing a trip only after two or more operations of the coincidence detector occurring on con-
secutive power cycles. This can be implemented by setting
87PC RESET
to “0” and using digital elements to count the num-
ber of coincidences.
Figure 9–8: SECURE TRIPPING ON THE 2ND COINCIDENCE OF THE 87PC ELEMENT
Counter operates on
second operation of
87PC, producing a trip
second operation of
87PC during two
consecutive cycles
831790A1.CDR