Earthing arrangement for high and medium voltage networks - has solenoid operated interlock on access flap with additional switch in solenoid circuit operable from outside of housing

摘要

The entry to the earthing bar (27) is covered by a flap(20) which is locked by a bolt (11) when in the closed position. The bolt can be raised by a solenoid (12) when the network isolator is in the appropriate position, thus allowing the flap to be opened and an earthing connector (30) to be inserted. In order that the solenoid is not energised for the entire time that the network isolator is in the position where earthing is permitted a pushbutton switch, with contacts in series with the solenoid, is included in the earthing box lid. To open the flap the button is pressed to raise the bolt. In the open position the bolt is held up and the buttpn can be released. The end of the solenoid plunger (40) opposite the bolt operates a mercury switch in the isolator circuit to prevent closure when the flap is open.