Weak-End Infeed Logic - ABB REL650 Applications Manual

1MRK 506 334-UUS A
12.3.2.2
Application manual
send a communication signal to the protection B:2 at remote end, which is measuring a
fault in reverse direction.
CLOSED
Strong
source
A:1
A
CLOSED
A:2
ANSI99000043 V1 EN
Figure 197: Current distribution for a fault close to B side when all breakers are closed
When the breaker B: 1 opens for clearing the fault, the fault current through B: 2 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 B:2 at B side.
CLOSED
Strong
source
A:1
A
CLOSED
A:2
ANSI99000044 V1 EN
Figure 198: Current distribution for a fault close to B side when breaker B: 1 has
opened
To handle this the send signal CS from B: 2 is held back until the reverse zone IRVL has
reset and the tDelayRev time has elapsed. To achieve this reverse zone on the distance
protection shall be connected to input IREV 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 IFWD or the general BLOCK input.

Weak-end infeed logic

Permissive communication schemes can basically operate only when the protection in the
remote terminal can detect the fault. The detection requires a sufficient minimum fault
current, normally >20% of In. 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
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 12
Scheme communication
Weak
source
B
Weak
source
403