ABB RELION REX640 Technical Manual page 1270

Protection and control

Hide thumbs Also See for RELION REX640:

Table of Contents

Protection related functions

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

The weak-end infeed logic should be used only in permissive schemes.

Setting guidelines for current reversal logic

reset time of the communication channel. A minimum setting of 40 ms is

recommended. A long

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.

percent of the breaker operate time, but to a minimum of 20 ms.

Avoid using the WEI function at both feeder ends. It can only be enabled

at the weak end.

Reversal reset time : Set the Reversal reset time setting to the maximum

Reversal reset time setting increases the security against

Reversal time : Set the start delay Reversal time setting to less than 80

1MRS759142 F

Technical Manual