ABB RELION REX640, Техническое руководство, Страница: 1270 / 1960

B1. Thus, when the breaker at Relay B1 opens, the direction of the fault current at the
healthy feeder (Feeder 2) is reversed.
Figure 720: The circuit breaker at Relay B1 opens and creates a current reversal condition
Relay A2 is still sending the CS signal because of the reset time delay of the forward
zone of Relay A2 when the overreaching zone of 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 by using the reverse-looking zone (Z3) to recognize the
fault in reverse direction and temporarily block the operation of DSOCPSCH due to
the current reversal condition. This is used in CRWPSCH.
Weak-end infeed logic
Avoid using the WEI function at both feeder ends. It can only be enabled
at the weak end.
The weak-end infeed logic should be used only in permissive schemes.
Setting guidelines for current reversal logic
Setting
Reversal reset time: Set the Reversal reset time setting to the maximum
reset time of the communication channel. A minimum setting of 40 ms is
recommended. A long
Reversal reset time setting increases the security against
unwanted tripping, but delays the fault clearing if the fault develops in one feeder
and involves the other. However, the probability of this type of fault is small.
Setting
Reversal time: Set the start delay Reversal time setting to less than 80
percent of the breaker operate time, but to a minimum of 20 ms.
Protection related functions 1MRS759142 F
1270 REX640
Technical Manual