Setting The Number Of Operations Thresholds; Setting The Operating Time Thresholds; Setting The Excessive Fault Frequency Thresholds; Lockout Reset - GE MiCOM P40 Agile Technical Manual

P44x/EN AP/Hb6
(AP) 5-122
5.1.2.2

Setting the Number of Operations Thresholds

Every operation of a circuit breaker results in some degree of wear for its components.
Therefore, routine maintenance, such as oiling of mechanisms, may be based upon the
number of operations. Suitable setting of the maintenance threshold will allow an alarm to be
raised, indicating when preventive maintenance is due. Should maintenance not be carried
out, the relay can be set to lockout the autoreclose function on reaching a second operations
threshold. This prevents further reclosure when the circuit breaker has not been maintained
to the standard demanded by the switchgear manufacturer's maintenance instructions.
Certain circuit breakers, such as oil circuit breakers (OCB's) 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 ('N° CB Ops Maint') may be set to indicate the requirement for
oil sampling for dielectric testing, or for more comprehensive maintenance. Again, the
lockout threshold ('N° CB Ops Lock') may be set to disable autoreclosure when repeated
further fault interruptions could not be guaranteed. This minimises the risk of oil fires or
explosion.
5.1.2.3

Setting the Operating Time Thresholds

Slow CB operation is also indicative of the need for mechanism maintenance. Therefore,
alarm and lockout thresholds ('CB Time Maint' and 'CB Time Lockout') are provided and
are settable in the range of 5 to 500 ms. This time is set in relation to the specified
interrupting time of the circuit breaker.
5.1.2.4

Setting the Excessive Fault Frequency Thresholds

A circuit breaker may be rated to break fault current a set number of times before
maintenance is required. However, successive circuit breaker operations in a short period of
time may result in the need for increased maintenance. For this reason it is possible to set a
frequent operations counter on the relay which allows the number of operations ('Fault Freq
Count') over a set time period ('Fault Freq Time') to be monitored. A separate alarm and
lockout threshold can be set.
5.1.2.5

Lockout reset

The 'Lockout Reset' and 'Reset Lockout by' setting cells in the menu are applicable to CB
Lockouts associated with manual circuit breaker closure, CB Condition monitoring (Number
of circuit breaker operations, for example) and auto-reclose lockouts.
5.1.2.6 Inputs/Outputs for CB Monitoring logic
The following DDB are available for CB monitoring (see section P44x/EN PL):
• Inputs
 Reset Lockout
 Reset All Values
• Outputs
 I^Maint Alarm
 I^Lock Out Alarm
 CB Ops Maint
 CB Ops Lockout
 CB Op Time Maint
 CB Op Time Lock
 F.F. Pre Lockout
 F.F. Lock
 Lockout Alarm
Application Notes
MiCOM P40 Agile P442, P444