Patent ID: 8018235
Filing Date: 2011-09-13
Classification: G01R,H02H

Abstract:
1. A ground fault detection device comprising: a sense coil comprising a secondary winding surrounding a line conductor and a neutral conductor, the line conductor and the neutral conductor forming a primary winding; a non-resonant circuit voltage oscillator generating an oscillation signal independent of and connected in series with the secondary winding to drive an oscillation component; and at least one of a detector or an amplifier coupled to the secondary winding to determine a magnitude of at least one of a neutral-to-ground fault or a line-to-ground fault and wherein the at least one detector or amplifier monitors a current of the secondary winding to detect the neutral-to-ground fault, the at least one detector or amplifier comprising a current detector, detecting a current increase, the current increase indicative of a neutral-to-ground fault, wherein the current detector comprises a virtual inductor, an impedance of the virtual inductor being proportional to an impedance of magnetizing inductance of the sense coil, whereby current in both inductances is proportional and the proportion is frequency independent, to provide an accurate fault measurement.