Current Reversal And Weak-End Infeed Logic For Residual Overcurrent Protection Ecrwpsch (85) - ABB REL650 series Technical Manual

1MRK 506 335-UUS A
12.6
12.6.1
12.6.2
Technical manual
Current reversal and weak-end infeed logic for residual
overcurrent protection ECRWPSCH (85)
Identification
Function description
Current reversal and weak-end infeed
logic for residual overcurrent protection
Functionality
The Current reversal and weak-end infeed logic for residual overcurrent protection
ECRWPSCH (85) is a supplement to Scheme communication logic for residual
overcurrent protection ECPSCH (85).
To achieve fast fault clearing for all ground faults on the line, the directional ground-fault
protection function can be supported with logic that uses communication channels.
The 650 series IEDs have for this reason available additions to scheme communication
logic.
If parallel lines are connected to common busbars at both terminals, overreaching
permissive communication schemes can trip unselectively due to fault current reversal.
This unwanted tripping affects the healthy line when a fault is cleared on the other line.
This lack of security can result in a total loss of interconnection between the two buses. To
avoid this type of disturbance, a fault current reversal logic (transient blocking logic) can
be used.
Permissive communication schemes for residual overcurrent protection can basically
operate only when the protection in the remote IED can detect the fault. The detection
requires a sufficient minimum residual fault current, out from this IED. The fault current
can be too low due to an opened breaker or high-positive and/or zero-sequence source
impedance behind this IED. To overcome these conditions, weak-end infeed (WEI) echo
logic is used. The weak-end infeed echo is limited to 200 ms to avoid channel lockup.
Scheme communication
IEC 61850 IEC 60617
identification identification
ECRWPSCH -
Section 12
ANSI/IEEE C37.2
device number
85
523