Sel SEL-421 - UBDURD: DCUB Disable Delay; UBEND: DCUB Duration Delay; DCUB Relay Word Bits

R.1.102
SEL-421 Relay Reference Manual Date Code 20111215
Protection Functions
Directional Comparison Unblocking Scheme Logic
UBDURD: DCUB Disable Delay
This timer prevents high-speed tripping via the POTT scheme logic after a
settable time following a loss-of-channel condition; a typical setting is nine
cycles. Channel 1 and Channel 2 logic use separate timers but have this same
delay setting.
UBEND: DCUB Duration Delay
This timer determines the minimum time before the relay declares a loss-of-
channel condition; a typical setting is 0.5 cycles. Channel 1 and Channel 2
logic use separate timers but have this same delay setting.
Tabl e 1 . 69 DCU B Re l ay Wo rd B its
Name Description
UBB1 Block permissive trip on Receiver 1
PTRX1 Permissive trip received on Channel 1
UBB2 Block permissive trip on Receiver 2
PTXR2 Permissive trip received on Channel 2
UBB Block permissive trip received on Channel 1 or Channel 2
PTRX Permissive trip received on Channel 1 and Channel 2