Patent ID: 8570181

Claim:
A ground fault detection device comprising: line and neutral conductors configured to connect an AC power source and a load; a differential current transformer comprising: a toroid, through which the line and neutral conductors pass, a first secondary winding wound on the toroid configured to generate a current in response to an imbalance of magnetic flux in the toroid, and a second secondary winding wound on the toroid; a differential ground fault detector electrically connected to the first secondary winding of the differential current transformer and configured to compare the current generated in the first secondary winding to a predetermined threshold; a controller configured to control a test stimulus signal to be generated in the second secondary winding; and a DC power supply electrically connected to the second secondary winding wound on the toroid of the differential current transformer, wherein the controller is configured to control the DC power supply to generate the test stimulus signal in the second secondary winding.