P.4.12
SEL-411L Relay Protection Manual Date Code 20151029
Autoreclosing and Synchronism-Check
Two-Circuit-Breaker Autoreclosing
SPLSHT Asserted (Last Shot). The recloser exits the 79CY1 state via
three methods while SPLSHT is asserted:
➤ If no further trip conditions occur and timer SPRCD expires,
the recloser returns to the reset states BKnRS.
➤ If a fault occurs during the SPRCD reclaim time, then the
recloser asserts Relay Word bit 3PARC if all three-pole reclose
conditions are satisfied and proceeds to the autoreclose three-
pole cycle state 79CY3.
➤ If a fault occurs during the SPRCD reclaim time and the three-
pole reclose conditions are not satisfied (E3PRn is logical 0, for
example), then the recloser exits the 79CY1 cycle state and
goes to the lockout state BknLO.
Lockout State from 79CY1
The recloser goes to lockout (BKnLO) when the number of trips exceeds the
maximum number of shots (NSPSHOT), supervision condition SPnCLS 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 4.14 and Figure 4.15 show the two circuit breaker three-pole
autoreclose cycle 79CY3 when E79 := Y and E79 := Y1, respectively. The
cycle starts when Relay Word bit 3PARC asserts. The recloser freezes
calculation of the number of breakers, the leader circuit breaker, and the
follower circuit breaker. Depending on the calculation, the recloser asserts the
appropriate Relay Word bits NBK0, NBK1, NBK2, LEADBK0, LEADBK1,
LEADBK2, FOLBK0, FOLBK1, and FOLBK2. The recloser checks
SEL
OGIC control equation 79SKP at this point to determine whether to
increment the shot counter.
The recloser waits for 3POLINE to assert:
➤ if E79 := Y, 3POLINE asserts when both breakers (leader and
follower) open (see Figure 4.6)
➤ if E79 := Y1, 3POLINE asserts when at least one breaker
(leader or follower) opens (see Figure 4.7)
If 3POLINE asserts, the recloser proceeds to timing 3POID1 (Three-Pole
Open Interval 1 Delay). In applications where 3POLINE may not reliably
assert while in the 79CY3 state, we recommend forcing the autoreclose cycle
into a drive-to-lockout state (79DTL = 1) after a fixed time delay. You can do
this by using the entry into the cycle state (79CY3 = 1) as an input to a
conditioning timer. The conditioning timer applies a pickup delay, and the
relay 79DTL setting includes the conditioning timer output. The time delay
should be long enough to allow normal breaker operation to occur, while
preventing the autoreclose logic from stalling while waiting indefinitely for
3POLINE to assert. If SEL
OGIC control equation 3PFARC (Three-Pole Fast
ARC Enable) is asserted, the recloser times the open interval time from setting
3PFOID (Three-Pole Fast Open Interval Delay). When E79 := Y1, a Three-
Pole Open Interval Supervision Condition (3POISC) must be satisfied before
the recloser can proceed to timing 3POID1. If the supervisory condition is not
met within the duration of timer 3POISD (Three-Pole Open Interval
Supervision Delay), the recloser goes to lockout.
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