| 摘要 |
In a first aspect, a device is provided 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 are each coupled between a source and a load, the neutral conductor is coupled to ground at the source, and 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 includes 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. The device also includes a second circuit coupled to the secondary winding, wherein the second circuit includes an AC signal source that provides an AC signal at a specified amplitude and a specified frequency to the secondary winding. The second circuit also provides a second detection signal if an impedance between the neutral conductor and ground is less than a second predetermined threshold. Numerous other aspects are also provided.
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