ABB REX 521 Technical Reference Manual, Standard Configurations page 125

1MRS 751802-MUM Protection Relay
Technical Reference Manual, Standard Configurations
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OC-blocking signal
from outgoing-feeders
to 3I>>> stage
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REX 521
REX 521
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OC-blocking signal to
HV-relay (3I>> START)
Circuit breaker failure
protection
Io>>> TRIP to breaker on
HV side of transformer
CLOSE circuit breaker
TRIP circuit breaker
125