U.5.33
Date Code 20020501 User’s Guide SEL-421/SEL-421-1 Relay
Front-Panel Operations
Operation and Target LEDs
The 51 target LED illuminates if a time-overcurrent element has timed out.
The relay lights this LED if any of the selectable operating quantity inverse-
time overcurrent elements 51S1T, 51S2T, and 51S3T assert.
Recloser Status
The 79 RESET and the 79 LOCKOUT target LEDs show the operating status
of the SEL-421 Relay reclosing function. The 79 RESET LED indicates that
the relay recloser is in the reset or ready-to-reclose state for Circuit Breaker 1
(Relay Word bit BK1RS is asserted). The 79 LOCKOUT target illuminates
when the relay has completed the reclose attempts unsuccessfully (a drive-to-
lockout condition), or when other programmed lockout conditions exist. If the
79 RESET and the 79 LOCKOUT LEDs are not lit, the relay is in the cycle
state for Circuit Breaker 1. See Section 2: Auto-Reclose and Synchronism
Check in the Reference Manual for complete information on the SEL-421
Relay recloser function.
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