GE P24DM, Technical Manual

Page: 282 / 600

6 CB STATE MONITORING
CB State monitoring is used to verify the open or closed state of a circuit breaker. Most circuit breakers have
auxiliary contacts through which they transmit their status (open or closed) to control equipment such as IEDs.
These auxiliary contacts are known as:
● 52A for contacts that follow the state of the CB
●
52B for contacts that are in opposition to the state of the CB
This device can be set to monitor both of these types of circuit breaker state indication. If the state is unknown for
some reason, an alarm can be raised.
Some CBs provide both sets of contacts. If this is the case, these contacts will normally be in opposite states.
Should both sets of contacts be open, this would indicate one of the following conditions:
● Auxiliary contacts/wiring defective
●
Circuit Breaker (CB) is defective
● CB is in isolated position
Should both sets of contacts be closed, only one of the following two conditions would apply:
●
Auxiliary contacts/wiring defective
● Circuit Breaker (CB) is defective
If any of the above conditions exist, an alarm will be issued after a 5 s time delay. An output contact can be
assigned to this function via the programmable scheme logic (PSL). The time delay is set to avoid unwanted
operation during normal switching duties.
In the CB CONTROL column there is a setting called CB Status Input. This cell can be set at one of the following
four options:
●
None
● 52A
●
52B
● Both 52A and 52B
Where
None
is selected no CB status is available. Where only 52A is used on its own then the device will assume a
52B signal opposite to the 52A signal. Circuit breaker status information will be available in this case but no
discrepancy alarm will be available. The above is also true where only a 52B is used. If both 52A and 52B are used
then status information will be available and in addition a discrepancy alarm will be possible, according to the
following table:
Auxiliary Contact Position CB State Detected Action
52A 52B
Open Closed Breaker open Circuit breaker healthy
Closed Open Breaker closed Circuit breaker healthy
Closed Closed CB failure
Alarm raised if the condition persists for greater than
5 s
Open Open State unknown
Alarm raised if the condition persists for greater than
5 s
Chapter 13 - Monitoring and Control P24xM
258 P24xM-TM-EN-2.1