Sel 411L - Page 468

P.4.14
SEL-411L Relay Protection Manual Date Code 20151029
Autoreclosing and Synchronism-Check
Two-Circuit-Breaker Autoreclosing
3PLSHT Asserted (Last Shot)
The recloser exits the 79CY3 state via two methods while 3PLSHT is
asserted:
➤ If no further trip conditions occur and timer 3PRCD expires,
the recloser returns to the reset states BKnRS.
➤ If a fault occurs during the 3PRCD reclaim time and 3PLSHT
is asserted, then the recloser goes to lockout BKnLO.
Lockout State from 79CY3
The recloser goes to lockout (BKnLO) when the number of trips exceeds the
maximum number of shots (N3PSHOT), supervision condition 3PnCLS 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.
Single- and Three-Pole Mode
The single- and three-pole mode (SPAR/3PAR) uses elements of both the
single-pole mode (SPAR) and the three-pole mode (3PAR). Reclosing begins
after a single-pole trip in the single-pole cycle 79CY1 with a valid SPARC as
described in Single-Pole Mode. The recloser closes the circuit breakers and
proceeds to the reclaim timer SPRCD. If a fault occurs during the SPRCD
reclaim time and SPLSHT is asserted, then the recloser asserts Relay Word bit
3PARC if all three-pole reclose conditions are satisfied. Upon asserting
3PARC, the recloser exits the 79CY1 cycle state and goes to the beginning of
the three-pole autoreclose cycle state 79CY3. The recloser proceeds through
the 79CY3 state and exits this state as described in Three-Pole Mode.
Three-Pole Priority
If a single-pole autoreclose cycle is in progress (79CY1) and the relay receives
an initiation for three-pole reclosing (3PRI), the recloser immediately starts a
three-pole autoreclose cycle (79CY3).
Active Circuit
Breakers
The following three Relay Word bits describe when Circuit Breaker BK1 and
Circuit Breaker BK2 are active for the autoreclose logic:
➤ NBK0, No Breaker Active in Reclose Scheme
➤ NBK1, One Breaker Active in Reclose Scheme
➤ NBK2, Two Breakers Active in Reclose Scheme
Leader and Follower
Circuit Breakers
One circuit breaker is the leader and the other is the follower for circuit
breaker-and-a-half and ring-bus arrangements. Figure 4.2 illustrates a multiple
circuit breaker arrangement. The leader recloses first. If the leader recloses
successfully, the follower also typically recloses.