Blocking Signal Overview - ABB REX 521 Technical Reference Manual, Standard Configurations

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9.3.5.
Protection Relay
Technical Reference Manual, Standard Configurations
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1
OC-blocking signal from
MV-relay to 3I>> stage
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Blocking signal overview

To clarify the blockings between the different levels in the first three application
examples (chapters 9.1., 9.2. and 9.3.) the signals are presented in the figure below.
CB
DC
REX 521
REX 521
0
1
Circuit breaker failure
protection
CLOSE circuit breaker
TRIP circuit breaker
133