ABB REX 521 Technical Reference Manual, Standard Configurations page 105

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Protection Relay
Technical Reference Manual, Standard Configurations
TRIP circuit breaker
CLOSE circuit breaker
Blocking signal to the incoming
feeder (START 3I>>)
Circuit-breaker failure
protection
Breaker wear alarm
Internal relay fault
Blocking signal from
the residual voltage relay
to the Io>
*) Power flow direction
REX 521
105