Earthing switches are commonly used and installed in medium voltage switchgear. When isolating any of the feeders (incoming or outgoing) for maintenance, the feeder must be earthed by closing the earthing switch to
discharge any static charge carried by the feeder. Earthing switches are mounted separately ahead of the switchgear-cable basement (Fig a) or in the base of LBS (Fig b) or just underneath the CB (Fig c).
The switchgear manufacturer must mechanically and electrically interlock the earthing switch with the CB or LBS to avoid severe symmetrical short circuit if they are closed simultaneously.
Advertisement 
