Patent ID: 8908339
Filing Date: 2014-12-09
Classification: H02H

Abstract:
1. A device for use with an AC power system that includes a line conductor, a neutral conductor and a transformer, the line conductor and the neutral conductor each coupled between a source and a load, the neutral conductor coupled to ground at the source, wherein the transformer includes a first primary winding coupled in series with the line conductor, a second primary winding coupled in series with the neutral conductor, and a secondary winding, the device comprising: a first circuit coupled to the secondary winding, wherein the first circuit provides a first detection signal if a current from the line conductor to ground exceeds a first predetermined threshold; and a second circuit coupled to the secondary winding, wherein the second circuit includes an AC signal source that supplies an AC signal, which exists prior to coupling to the secondary winding, at a specified amplitude and a specified frequency to the secondary winding, wherein a response from the secondary winding is at a same frequency as the specified frequency, and wherein the second circuit provides a second detection signal if an impedance between the neutral conductor and ground is less than a second predetermined threshold.