Patent ID: 9547032
Date: 2017-01-17
CPC Classifications: G01R,H02H

Claim:
1. An apparatus comprising: a signal generation module that injects a signal in a pilot conductor, the signal comprising one or more alternating current (“AC”) components, each AC component of the one or more AC components comprising a frequency different from other AC components of the one or more AC components, wherein current in the pilot conductor is injected in a grounding conductor of a set of power cables connecting a power source to a load, the grounding conductor connected to a ground return, wherein the set of power cables, the grounding conductor and the pilot conductor are combined from the power source to the load; a frequency change module that periodically changes an AC component characteristic of each of the one or more AC components; a current monitor module that monitors current in at least one of the pilot conductor and the ground return; an AC detection module that determines an AC current corresponding to each frequency of the one or more AC components present in the current monitored by the current monitor module; an AC threshold module that determines if one or more of the AC currents determined by the AC detection module is below an AC threshold; and a trip module that opens a contact in response to the AC threshold module determining that at least one of the AC currents is below an AC threshold for longer than an AC current time threshold, the contact disconnecting the power source from the set of power cables.