5.176
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Functions
Synchronism Check
For circuit breaker status, make the following 52A auxiliary contact connec-
tions from the circuit breaker and switch to control inputs on the SEL-421:
➤ Circuit breaker BK3 to IN103
➤ Generator switch to IN104
These input connections are for this application example only; use relay
inputs that are appropriate for your system.
Set the ALTS2 SEL
OGIC control equation to assert when Circuit Breaker
BK3 is open and the generator switch is closed.
ALTS2 := NOT IN103 AND IN104. Alternative Synchronism Source 2
(SEL
OGIC Equation)
Example 5.1
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