7SR18 Description Of Operation
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4.8 Circuit Breaker
This menu includes relay settings applicable to manual close (MC) functionality.
‘CB Failed To Open’ and ‘CB Failed to Close’ features are used to confirm that a CB has not responded correctly
to each Trip and Close Command.
Close CB Pulse
The duration of the Close CB Pulse is settable to allow a range of CBs to be used. The Close CB Pulse must be
long enough for the CB to physically close.
The Close pulse will be terminated if any protection pick-up operates or a trip occurs. This is to prevent Close and
Trip Command pulses existing simultaneously. A 79 Close Onto Fault (auto-reclose option) output is given if a
pick-up or trip operates during the Close Pulse. This can be independently wired to Lockout.
The output CB Fail to Close is issued if the CB is not closed at the end of the close pulse, Close CB Pulse.
CB Control Trip Time
When this is set to Enabled, the relay will measure the CB trip time following operation of either a CB control
open output or a CB Trip output. The trip time is displayed by the MAINTENANCE METERS > CB Trip Time
meter.
When this is set to Disabled, the relay will measure the trip time following operation of a CB Trip output only.
Operation of a CB control open output will then not cause the trip time to be measured.
Open CB Pulse
The duration of the CB open pulse is user settable to allow a range of CBs to be used.
The CB open pulse must be long enough for the CB to physically open.
CB Travel Alarm
The CB Open and CB Closed binary inputs are continually monitored to track the CB Status.
The CB should only ever be in one of three states: -
CB Open
binary input
CB Closed
binary input
CB is Open 1 0
CB is Closed 0 1
CB is Travelling between the above 2 states 0 0
The Relay goes to Lockout and the CB Alarm output is given where the Travelling condition exists for longer than
the CB Travel Alarm setting.
An instantaneous CB Alarm is given for a 1/1 state – i.e. where the CB indicates it is both Open and Closed at
the same time.
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