An apparatus includes a signal generation module that injects a signal in a pilot conductor with one or more AC components. Pilot conductor current is injected in a grounding conductor of power cables connecting a source to a load. A current monitor module monitors affected current in the pilot conductor. A DC detection module determines a DC current present in the current. A DC minimum threshold module determines if the DC current is below a DC current threshold. An AC detection module determines an AC current of each frequency of the AC components. An AC threshold module determines if any of the AC currents is below an AC threshold. A trip module opens a contact after determining that the DC current is below the DC current minimum threshold and/or determining that at least one of the AC currents is below an AC threshold. The contact disconnects the source.