ABB REX 521 Technical Reference Manual, Standard Configurations page 173

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Protection Relay
Technical Reference Manual, Standard Configurations
TRIP1 circuit breaker
CLOSE circuit breaker
3I> -> TRIP2 to the
HV side circuit breaker
Circuit-breaker failure
protection
OC blocking signal to the
HV-side 3I>> stage (3I> START)
OC blocking signal to the
3I>> stages (3I>-> START)
Internal relay fault
OC blocking signal
from the outgoing feeders
and the bus sectionalizer
to the 3I>> stage
TCS1
TempAlarm
Mains
ACFail
REX 521
173