Figure 94 - Change In Coil Charge - GE CB Watch 3 User Manual

• The "Mean coil current" is the average level of the coil current during the
operations
• The "Coil actuation charge" is
area under the "coil current /vs/ time" curve and is the integration of
time, it is the
the current multiplied by the time (A x ms).
The diagram below shows that the coil actuation charge can be longer (green curve)
if the latch is sticking for example and the CB does not start moving as early as on the
pink normal curve.
A damage coil will also show a higher current and a longer coil charge.
Please note that in some protection schemes, both the opening 1 and backup opening 2
relays are fired "simultaneously" rather than only if the other one fails to open the
breaker. In this case, it is impossible to predict which of the relay will operate which pole
of the circuit breaker. The CBW3 system determines which signals it receives first and
displays the corresponding current value. So please be aware that we could end up with
different poles being triggered by different relays and so displaying a mixture of current
values against both open1 and open2.
Data is recorded for the first 300ms (acquisition time) and a "coil current /vs/ time" curve
is displayed in the HMI and stored:
CB Watch 3 User Manual
a measure used to reflect both coil current and actuation
Figure 89 – Change in coil charge
v6.3 - May 2019 Page 58 of 100