Weak-End Infeed Logic - ABB REC670 Applications Manual

1MRK 511 401-UUS A
15.2.2.2
Bay control REC670 2.2 ANSI
Application manual
CLOSED
Strong
source
A:1
A
CLOSED
A:2
ANSI99000043 V1 EN-US
Figure 193: Current distribution for a fault close to B side when all breakers are
closed
When the breaker B1 opens for clearing the fault, the fault current through B2 bay will
invert. If the communication signal has not reset at the same time as the distance
protection function used in the teleprotection scheme has switched on to forward
direction, we will have an unwanted operation of breaker B2 at B side.
CLOSED
Strong
source
A:1
A
CLOSED
A:2
ANSI99000044 V1 EN-US
Figure 194: Current distribution for a fault close to B side when breaker B1 has
opened
To handle this the send signal CS or CSLn from B2 is held back until the reverse zone
IRVLn has reset and the tDelayRev time has been elapsed. To achieve this the reverse
zone on the distance protection shall be connected to input IRV and the output IRVL
shall be connected to input BLKCS on the communication function block ZCPSCH.
The function can be blocked by activating the input IRVBLK or the general BLOCK
input.

Weak-end infeed logic

Permissive communication schemes can basically operate only when the protection in
the remote IED can detect the fault. The detection requires a sufficient minimum fault
current, normally >20% of . The fault current can be too low due to an open breaker or
low short-circuit power of the source. To overcome these conditions, weak-end infeed
(WEI) echo logic is used. The fault current can also be initially too low due to the fault
current distribution. Here, the fault current increases when the breaker opens at the
strong terminal, and a sequential tripping is achieved. This requires a detection of the
fault by an independent tripping zone 1. To avoid sequential tripping as described, and
CLOSED
FAULT
LINE 1
B:1
CLOSED
LINE 2
B:2
en99000043_ansi.vsd
FAULT OPEN
LINE 1
B:1
B
CLOSED
LINE 2
B:2
en99000044_ansi.vsd
Section 15
Scheme communication
Weak
source
B
Weak
source
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