A ballast circuit (100) includes a ground fault detector (200).

Disclosed is a helically wound core of ferrous material (14) used as a differential current sensor core in the ground fault sensor of a ground fault interrupter circuit.

Ground fault sensing circuit is provided for operator hazard protection.

A ground fault detector may be combined with one or more of these systems for detecting a ground fault in the circuit to be protected.

The detection path also comprises a short circuit detector (3) with a first and a second detector input (31, 32) and a detector output (33), wherein the first detector input (31) is coupled to the filter (2).

When the high-frequency current is detected, the ground fault detector provides an output signal (150) which may be used to disconnect the load from the ballast circuit.

A problem exists in that a ground fault detector is not easily connected to an existing system.