ABB REX 521 Technical Reference Manual, Standard Configurations page 189

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Protection Relay
Technical Reference Manual, Standard Configurations
TRIP circuit breaker
CLOSE circuit breaker
Io>>> TRIP to breaker on
HV side of transformer
Circuit-breaker failure
protection
OC blocking signal to
the HV relay (3I>> START)
Internal relay fault
OC blocking signal
from the outgoing feeders
to the 3I>>> stage
TCS1
TempAlarm
Mains
ACFail
REX 521
189