A Controlled switching device facilitates the close – open operation of the CB contacts at a pre-determined point of the electrical reference signal waveform to minimize switching surges.
Controlled Closing with CSD
The controlled closing triggers closing mechanism of a single phase pole contacts of CB at a desired voltage point-on-wave angle of that phase. In this way it closes the circuit breaker poles one by one instead of closing all poles at a time. This synchronized operation reduces voltage or current transients during closing.
Controlled Opening with CSD
The CSD controls the contact separation of the poles of a CB one by one according to the current waveform of the respective phase. This is how, it controls the breaking by considering the arcing time to minimize transient voltage.
The CSD monitors current through the CB as a reference. It takes the signal from the current transformers associated with the CB. The CSD detects periodical current zero crossing of the current signal. The arcing time from the data sheet of the CB is set in the CSD. Depending on the pre determined arcing time the CSD triggers the pole opening. The CSD does it such a way that the current finally interrupt only on its natural zero crossing.
When C&R panel issues an opening command, the command first reaches to the CSD. Then, the CSD makes the command delayed. Actually, it waits to adjust the time and then sends the command to each individual CB pole separately to open each phase independently.