R.2.6
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
One-Circuit-Breaker Auto-Reclosing
SPLSHT Deasserted (Single-Pole Shot Remains). The recloser
exhibits four possible state transitions when SPLSHT is not asserted:
➤ If no further trip conditions occur, the recloser goes to the reset
state BK1RS after timer SPRCD expires.
➤ If a single-phase fault occurs while the SPRCD reclaim timer is
timing, the recloser asserts SPARC for single-pole initiate
conditions and returns to the beginning of the 79CY1 cycle
state; the recloser increments the shot counter and begins the
next open interval timer.
➤ If a multiphase fault occurs during the SPRCD reclaim time,
then the recloser asserts Relay Word bit 3PARC if all three-pole
reclose conditions are satisfied (E3PR1 is logical 1, for
example) and proceeds to the auto-reclose three-pole cycle
state 79CY3.
➤ If a multiphase fault occurs during the SPRCD reclaim time,
and the three-pole reclose conditions are not satisfied (E3PR1
is logical 0, for example), the recloser exits the 79CY1 cycle
state and goes to the lockout state BK1LO.
Lockout State from 79CY1
The recloser goes to lockout (BK1LO) when the number of trips exceeds the
maximum number of shots (NSPSHOT), supervision condition SP1CLS fails
to assert in BK1CLSD time, Relay Word bit 3POLINE asserts (for a circuit
breaker manual opening), the circuit breaker fails to close within BKCFD
time, or any time Relay Word bit 79DTL asserts.
Three-Pole Mode
Figure 2.11 shows the one circuit breaker auto-reclose cycle 79CY3. The
cycle starts when Relay Word bit 3PARC asserts. The recloser checks
SEL
OGIC control equation 79SKP at this point to determine whether to
increment the shot counter. The recloser waits as long as 15 cycles for the
circuit breaker to open, as indicated by Relay Word bit 3POLINE. If the
circuit breaker does not open in 15 cycles, the recloser goes to the lockout
state. The recloser begins timing 3POID1 (Three-Pole Open Interval 1 Delay)
when the circuit breaker opens. After the open interval time 3POID1 expires,
the relay asserts Relay Word bit BK1CL to reclose the circuit breaker if
supervisory condition 3P1CLS (Three-Pole BK1 Reclose Supervision) is
satisfied within the duration of timer BK1CLSD (BK1 Reclose Supervision
Delay).
At the reclose command, the recloser starts timer BKCFD (Breaker Close
Failure Delay). If the circuit breaker fails to close, the recloser goes to lockout
(BK1LO) after timer BKCFD expires.
3PRCD Reclaim Timing
If the circuit breaker closes, the recloser starts timer 3PRCD (Three-Pole
Reclaim Time Delay). The recloser determines subsequent state transitions
during reclaim timing according to the status of Relay Word bit 3PLSHT
(Three-Pole Reclose Last Shot).
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