Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546
(OP) 5-179
OP
If an attempt to close the circuit breaker is being made and a protection trip signal is
generated, the protection trip command overrides the close command.
If the system check synchronism function is set, this can be enabled to supervise manual
circuit breaker close commands. A circuit breaker close output will only be issued if the
check synchronism criteria are satisfied. Different system check criteria can be selected for
control closing CB1 and CB2. A user settable time delay (Check Sync Time) is included to
supervise manual closure with check synchronizing criteria. If the check synchronism criteria
are not satisfied in this time period following a close command the relay will lockout and
alarm.
Before manual reclosure, in addition to a synchronism check, there is also a circuit breaker
healthy check, CB Healthy, which requires the circuit breaker to be capable of closing safely
(for example, having its closing spring fully charged and/or gas pressure sufficient for a close
and immediate fault trip), as indicated by DDB input CBx Healthy (x = 1 or 2). A user
settable time delay CB Healthy Time is included for manual closure with this check. If the
circuit breaker does not indicate a healthy condition in this time period following a close
command (DDB input is still low when the set time has elapsed) then the relay will lockout
the relevant circuit breaker and set an alarm.
If auto-reclose is used it may be desirable to block its operation when performing a manual
close. In general, the majority of faults following a manual closure will be permanent faults
and it will be undesirable to allow auto-reclose.
To ensure that auto-reclosing is not initiated for a manual circuit breaker closure on to a pre-
existing fault (switch on to fault), the AUTO-RECLOSE menu setting CB IS Time (circuit
breaker in service time) should be set for the desired time window. This setting ensures that
auto-reclose initiation is inhibited for a period equal to setting “CB IS Time” following a
manual circuit breaker closure. If a protection operation occurs during the inhibit period,
auto-reclosing is not initiated.
Following manual circuit breaker closure, if either a single phase or a three phase fault
occurs during the inhibit period, the circuit breaker is tripped three phase, but auto-reclose is
not locked out for this condition.
If the circuit breaker fails to respond to the control command (indicated by no change in the
state of CBx Status inputs) a ‘CBx Trip Fail’ or ‘CBx Close Fail’ alarm (x = 1 or 2) will be
generated after the relevant ‘Trip pulse Time’ or ‘Close Pulse Time’ has expired. These
alarms can be viewed on the relay LCD display, remotely via the relay communications, or
can be assigned to operate output contacts for annunciation using the relays programmable
scheme logic (PSL).
Note: CB Healthy Time timer and Check Sync Time timer described in this
menu section are applicable to manual circuit breaker operations only.
These settings are duplicated in the auto-reclose menu for auto-
reclose applications.
For the description of settings and commands related to the various methods for resetting
circuit breaker lockouts, refer to section 5.6.6.18 - Reset CB Lockout.
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