6.20
SEL-351A Relay Instruction Manual Date Code 20080213
Close and Reclose Logic
Reclosing Relay
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
CLOSE off until the circuit breaker status indication tells the relay that the
breaker is closed. The circuit breaker anti-pump circuitry should take care of
the TRIP and CLOSE being on together for a short period of time.
Other Settings Considerations
1. In the preceding additional setting example, the reclose initiate
setting (79RI) includes input IN101, that is connected to a 52a
breaker auxiliary contact (52A = IN101).
79RI = !52A
If a 52b breaker auxiliary contact is connected to input IN101
(52A = !IN101), the reclose initiate setting (79RI) remains the
same.
2. If no reclose initiate supervision is desired, make the following
setting:
79RIS = 1 (numeral 1)
Setting 79RIS = logical 1 at all times. Any time a logical 0 to
logical 1 transition is detected by setting 79RI, open interval
timing will be initiated (unless prevented by other means).
3. If the following setting is made:
79RI = 0 (numeral 0)
reclosing will never take place (reclosing is never initiated).
The reclosing relay is effectively inoperative.
Courtesy of NationalSwitchgear.com
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