ABB RELION REX640 Technical Manual page 1278

Protection and control

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Protection related functions

Figure 724: Fault occurs at one of the parallel lines. CS=carrier signal sending, CR=carrier signal

The faulty feeder (Feeder 1) is not simultaneously tripped at both ends and, for

example, the circuit breaker closer to the fault at Relay B1 may be tripped faster than

the breaker at bus A. As a result, when the breaker at Relay B1 opens, the direction of

the fault current at the healthy feeder (Feeder 2) is reversed.

Figure 725: Circuit breaker at Relay B1 opens and creates a current reversal condition. CS=carrier signal

sending, CR=carrier signal receiving

Relay A2 still sends the CS signal because of the reset time delay of the forward

direction residual overcurrent function of Relay A2. When Relay B2 starts to

recognize the fault in the forward direction, Relay B2 can malfunction and trip the

breaker of the healthy feeder.

This problem can be solved using the reverse directional residual overcurrent

function to recognize the fault in reverse direction and temporarily block the

operation of the scheme communication logic due to the current reversal condition.

This is used in RCRWPSCH.

1MRS759142 F

Technical Manual