Breaker opening time is displayed on the LCD display under MEASUREMENTS menu.
The CB Open Supervision logic is explained in following diagram:
Figure 6: CB open supervision logic
2.8.2 CB Open Operation Alarm
Every circuit breaker operation results in some degree of wear for its components. Therefore routine
maintenance, such as oiling of mechanisms, may be based on the number of operations. Suitable
setting of the maintenance threshold will allow an alarm to be raised, indicating when preventative
maintenance is due.
Some circuit breakers, such as oil circuit breakers (OCBs) can only perform a certain number of fault
interruptions before requiring maintenance attention. This is because each fault interruption causes
carbonising of the oil, degrading its dielectric properties. The maintenance alarm threshold (setting
CB Open operations) may be set to indicate the requirement for oil dielectric testing, or for more
comprehensive maintenance.
For each circuit breaker trip operation, the relay records statistics. The relay monitors the number of
circuit breaker operation by maintaining two types of counter (1) Breaker Trip counter which is based
on the number of trips issued by the relay and (2) Breaker Operation counter which is the count of
total breaker operations and based on the status change of CB auxiliary contact wired to one of the
relay opto inputs. The relay compares the Breaker Operation Counter (BOC) with CB Open
Operations (CB Open Oper) setting and generates CB Open Operation alarm when counter exceeds
the set value, indicating that the preventative maintenance is due. The alarm message is displayed on
LCD display and START LED starts blinking. The associated event is stored in Event Record.
2.9 CB Control
There are several types of circuit breaker;
• CBs with no auxiliary contacts
• CBs with 52A contacts (where the auxiliary contact follows the state of the CB)
• CBs with 52B contacts (where the auxiliary contact is in the opposite state the state of the CB)
• CBs with both 52A and 52B contacts
Circuit Breaker control is only possible if the circuit breaker in question provides auxiliary contacts.
For local control, the CB control by cell should be set accordingly.
The length of the trip and close control pulses can be set via the Open Pulse Time and Close Pulse
Time settings respectively. These should be set long enough to ensure the breaker has completed its
open or close cycle before the pulse has elapsed.
If an attempt to close the breaker is being made, and a protection trip signal is generated, the
protection trip command overrides the close command.
If the CB fails to respond to the control command (indicated by no change in the state of CB Status
inputs) an Open Fail alarm or Close Fail alarm is generated after the relevant trip or close pulses
have expired. These alarms can be viewed on the LCD display, remotely, or can be assigned to output
contacts.
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