Patent ID: 7916438

Claim:
A residual current device comprising: a circuit for detecting a current imbalance in an AC supply to a load indicative of a residual current and providing a corresponding output, a relay having contacts in the AC supply to the load, the relay contacts automatically closing when a current greater than a predetermined closing current is passed through the relay and being maintained closed by passing a holding current, less than the closing current, through the relay, the relay contacts automatically opening if the current through the relay falls below the holding current, and at least one further contact in series with the relay, the further contact being opened in response to an output from the current imbalance detecting circuit to interrupt the current flow through the relay and thereby disconnect the load, a charge storage device connected to the AC supply in parallel with the relay such that, upon application of power from the AC supply, current flows to the charge storage device to charge the latter up, and an electronic switch in series with the relay, the switch being turned on when the voltage on the charge storage device exceeds a predetermined threshold thereby to allow discharge of the charge storage device through the relay to provide a current exceeding the closing current, the AC supply thereafter providing a holding current for the relay at least when the supply is at a certain minimum voltage.