Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546
(OP) 5-63
OP
Listed below are some of the main features/requirements for a permissive overreaching
scheme:
The scheme requires a duplex signaling channel to prevent possible relay maloperation
due to spurious keying of the signaling equipment. This is necessary due to the fact that
the signaling channel is keyed for faults external to the protected line.
The POR scheme may be more advantageous than permissive underreach schemes for
the protection of short transmission lines, since the resistive coverage of the Zone 2
elements may be greater than that of the Zone 1 elements.
Current reversal guard logic is used to prevent healthy line protection maloperation for
the high speed current reversals experienced in double circuit lines, caused by
sequential opening of circuit breakers.
If the signaling channel fails, Basic distance scheme tripping will be available.
Note: The POR scheme also uses the reverse looking zone 4 of the relay as
a reverse fault detector. This is used in the current reversal logic and
in the optional weak infeed echo feature, shown dotted in Figure 38.
Send logi
c: Zone 2
Permissive trip logic: Zone 2 plus Channel Received
To Next Page
Loading...
