MA-037 - CB Watch 3 Operating Manual
v7.0 - May 2020
Page 64 of 118
The “zero current level” is by default set to 10%, but this value can be increased to 20% or
even 25% when the normal interrupted currents are quite low and we run the risk of 10%
being too close to the noise level.
If “ta” is not detected correctly, Z can be increased here:
HMI: Settings / Opening
Figure 94
–
zero current level
For each operation, the arcing time can be calculated as (ta
–
ts) and shown:
HMI: Measurements / last opening results
Figure 95
–
Arcing time
Arcing time alarm
To receive a warning when the breaker is not interrupting the arc fast enough and the arcing
time is too long, an alarm can be set against a maximum threshold:
HMI: Settings / Opening
Figure 96
–
Max arcing time threshold
Any alarm raised can be seen in the HMI:
HMI: Measurements / Alarms
Figure 97
–
Max arcing time alarm
To avoid false alarms if Z (described above) is less than 0.25% of the maximum value that
the CT can measure (as entered during setup), then
the arcing time is set to “max arcing
time -
2”
. This is done so that if Z is in the noise range of the
CT, then we don’t get any
“
excessive arcing time
”
nuisance alarms.
Note that in this case, a “
-
2ms” arcing time means that no max threshold has been set
!