ABB REX 521 Technical Reference Manual, Standard Configurations page 157

1MRS 751802-MUM Protection Relay
Technical Reference Manual, Standard Configurations
0
Second settings
1
OC-blocking signal
from outgoing-feeders
to 3I>>> stage
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1
OC-blocking signal to
HV-relay (3I>> START)
Uo>> Start to release blocking
of outgoing feeders
Circuit-breaker failure
protection
Uo>> TRIP to outgoing feeders
CLOSE circuit breaker
TRIP circuit breaker
157