21
CLEARING TIME (Clearing Time Log) (Input Modes 2 & 4 only)
The individual, phase-segregated CLEARING TIME logs use a timer, with the starting point at the beginning of the Trip
signal and ending with the cessation of current in each phase. Thus the Clearing Time for each phase is the sum of the
measured TRIP TIME and ARC TIME. The programmable A INPUT DELAY value has no effect on the CLEARING TIME.
This time represents the interrupter's overall efficiency, both mechanical and dielectric.
I
2
x T or I x T
Wear Duty
(Phase segregated per Trip Operation & Phase Segregated Cumulative Duty Log)
The individual, phase-segregated main contact wear duty logs employ a method of recording the destructive energy of
each arc incident that is programmable for I
2
x T or I x T. The measured current is (squared for
I
2
x T
and then) multiplied
by the time between measurement samples. The sum of these sample calculations is recorded in the main contact duty
wear logs for each phase, for each arc event. As subsequent arc events occur, the measured I
2
x T or I x T is added to the
phase-segregated main contact wear duty accumulation logs.
Note
:
If the CT Secondary phase currents are less than 7% of the Pickup Coil’s full-scale current rating and the breaker
trips, an ARC TIME of 000mS will be recorded. The values of
I
2
x T or I x T
recorded for such incidents are recorded
as
0
in the wear duty log.
Operations Counter
A counter will increment each time the circuit breaker opens. An Operations Count alarm limit can be programmed. When
the operations count reaches the limit an alarm is asserted.
Restrike Detection
The RESTRIKE setting is used to enable the detection of restrikes. When Restrike detection is activated, the ANSI
C37.100 criterion is used, which states that if an arc is extinguished, and more than ¼ cycle later it re-ignites, that is
considered a restrike (see Figure 22 on page 46). If a re-ignition takes place before the ¼ cycle period elapses, it is not
considered a restrike, but rather a continuance of the original arc. The first restrike detected will assert the alarm. Each CB
Trip record in the Circuit Breaker Event History will indicate whether a restrike has occurred by phase - true or false.
