Weak-end infeed (WEI) logic
Do not use the WEI function at both feeder ends. It can only be enabled
at the weak end.
The WEI logic is recommended to be used only in the permissive schemes.
Setting guidelines for current reversal logic
Reversal reset time
: This setting can be set 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 from one feeder to involve the other.
However, the probability of this type of fault is small.
Reversal time
: Set the start delay reversal time below 80 percent of the breaker
operate time, but to a minimum of 20 ms.
Setting guidelines for Weak-end infeed (WEI) logic
The WEI logic returns the received carrier signal with the ECHO output when it
receives the carrier signal (CR) if no fault has been detected by the forward and
reverse directional measuring elements and the duration is longer than the
Wei Crd
time
coordination time delay setting. To prevent the spurious carrier receive signals
from activating the WEI logic and causing unwanted communication, the
Wei Crd
time
setting can be set to "0.010 s".
5.13.7 Signals
5.13.7.1 RCRWPSCH Input signals
Table 1206: RCRWPSCH Input signals
Name Type Default Description
URES SIGNAL - Residual voltage
BLOCK BOOLEAN 0=False Block signal for acti-
vating the blocking
mode
BLK_IRV BOOLEAN 0=False Block of current rever-
sal function
BLK_WEI1 BOOLEAN 0=False Block of WEI Logic
BLK_WEI2 BOOLEAN 0=False Block of WEI logic due
to operation of other
protections
IRV BOOLEAN 0=False Activation of current
reversal logic
FF BOOLEAN 0=False Block of trip from
WEI logic through
fuse-failure function
Table continues on the next page
1MRS759142 F Protection related functions
REX640
Technical Manual
1279
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