Weak-End Infeed Logic - ABB RELION RET670 Applications Manual

1MRK 504 163-UUS A
16.6.2.2
16.6.3
Transformer protection RET670 2.2 ANSI
Application manual
CLOSED
Strong
source
A:1
A
CLOSED
A:2
ANSI99000044 V1 EN-US
Figure 392: 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 393 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.
Strong
CLOSED
source
A
ANSI99000054 V1 EN-US
Figure 393: Initial condition for weak-end infeed
Setting guidelines
The parameters for the current reversal and weak-end infeed logic for residual
overcurrent protection function are set via the local HMI or PCM600.
FAULT OPEN
LINE 1
B:1
B
CLOSED
LINE 2
B:2
en99000044_ansi.vsd
CLOSED
FAULT
LINE 1
Section 16
Scheme communication
Weak
source
Weak
source
B
en99000054_ansi.vsd
M15285-6 v5
IP15042-1 v1
M13933-4 v5
835