6.18
SEL-311C Relay Instruction Manual Date Code 20060320
Close and Reclose Logic
Reclosing Relay
The circuit breaker has to be closed (circuit breaker status 52A = logical 1) at
the instant of the first trip of the auto-reclose cycle in order for the SEL-311C
to successfully initiate reclosing and start timing on the first open interval. The
SEL-311C is not yet in the reclose cycle state (79CY = logical 0) at the instant
of the first trip.
Then for any subsequent trip operations in the auto-reclose cycle, the
SEL-311C is in the reclose cycle state (79CY = logical 1) and the SEL-311C
successfully initiates reclosing for each trip. Because of setting 79RIS = 52A
+ 79CY, successful reclose initiation in the reclose cycle state (79CY =
logical 1) is not dependent on the circuit breaker status (52A). This allows
successful reclose initiation for the case of an instantaneous trip, but the
circuit breaker status indication is slow—the instantaneous trip (reclose
initiation) occurs before the SEL-311C sees the circuit breaker close.
If a flashover occurs in a circuit breaker tank during an open interval (circuit
breaker open and the SEL-311C calls for a trip), the SEL-311C goes
immediately to lockout.
Additional Settings Example
The preceding settings example initiates open interval timing on rising edge of
the TRIP Relay Word bit. The following is an example of reclose initiation on
the opening of the circuit breaker.
Presume input IN101 is connected to a 52a circuit breaker auxiliary contact
(52A = IN101).
With setting:
79RI = !52A
the transition of the 52A Relay Word bit from logical 1 to logical 0 (breaker
opening) initiates open interval timing. Setting 79RI looks for a logical 0 to
logical 1 transition, thus Relay Word bit 52A is inverted in the 79RI setting
[!52A = NOT(52A)].
The reclose initiate supervision setting 79RIS supervises setting 79RI. With
settings:
79RI = !52A
79RIS = TRIP
the transition of the 52A Relay Word bit from logical 1 to logical 0 initiates
open interval timing only if the TRIP Relay Word bit is at logical 1 (TRIP =
logical 1). Thus, the TRIP Relay Word bit has to be asserted when the circuit
breaker opens in order to initiate open interval timing. With a long enough
setting of the Minimum Trip Duration Timer (TDURD), the TRIP Relay Word
bit will still be asserted to logical 1 when the circuit breaker opens (see
Figure 5.1 and Figure 5.2).
If the TRIP Relay Word bit is at logical 0 (TRIP = logical 0) when the circuit
breaker opens (logical 1 to logical 0 transition), the relay goes to the Lockout
State. This helps prevent reclose initiation for circuit breaker openings caused
by trips external to the relay.
If circuit breaker status indication (52A) is slow, additional setting change
ULCL = 0 (unlatch close; refer to Figure 6.1 and accompanying explanation)
may need to be made when 79RI = !52A. ULCL = 0 avoids going to lockout
prematurely for an instantaneous trip after an auto-reclose by not turning
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