Weak-End Infeed Logic - ABB REC670 Applications Manual

Section 15
Scheme communication
15.5.2.2
448
A1
A2
IEC99000043 V3 EN-US
Figure 195: Current distribution for a fault close to B side when all breakers are
closed
A1
A2
IEC99000044 V3 EN-US
Figure 196: Current distribution for a fault close to B side when breaker at B1 is
opened
When the breaker on the parallel line operates, the fault current on the healthy line
is reversed. The IED at B2 recognizes the fault in forward direction from reverse
direction before breaker operates. As IED at B2 already received permissive signal
from A2 and IED at B2 is now detecting the fault as forward fault, it will
immediately trip breaker at B2. To ensure that tripping at B2 should not occur, the
permissive overreaching function at B2 needs to be blocked by IRVL till the
received permissive signal from A2 is reset.
The IED at A2, where the forward direction element was initially activated, must
reset before the send signal is initiated from B2. The delayed reset of output signal
IRVL also ensures the send signal from IED B2 is held back till the forward
direction element is reset in IED A2.

Weak-end infeed logic

Figure 197 shows a typical system condition that can result in a missing operation.
Note that there is no fault current from node B. This causes that the IED at B
cannot detect the fault and trip the breaker in B. To cope with this situation, a
selectable weak-end infeed logic is provided for the permissive overreaching
scheme.
L1
B1
L2
B2
IEC9900043-2.vsd
L1
B1
L2
B2
IEC99000044-2.vsd
1MRK 511 401-UEN A
M15285-6 v5
Bay control REC670 2.2 IEC
Application manual