CB Watch 3 User Manual v6.3 - May 2019 Page 56 of 100
CONTROL CIRCUIT MONITORING
General description
This section covers monitoring the various CB command circuits and ensuring that any
open or close command, sent manually or by a protection relay, can be executed.
DC Supply
DC supply level
While a circuit breaker will fail to receive any command if there is no DC voltage present
or if it is extremely low, the time taken for the operation may be affected by the presence
of a lower than nominal DC voltage (as has been explained in section 4.4.3). This can
occur when the DC power is supplied by substation batteries not in optimal shape and
when several operations are taking place at the same time.
With the appropriate sensor installed, the CBW3 can continually monitor DC voltage
source 1 (and DC voltage source 2 if present) that supply the coil circuit voltage. The
values are displayed in the HMI:
HMI: Measurement / Sensors
Figure 84 – Continuous display of DC voltage for source 1 and 2
In addition, the voltage value at each opening or closing operation is stored with the
operation data and is displayed with the other last operation values:
HMI: Measurements/Last opening and closing results
Figure 85 – DC voltage in last operation measurements
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