Patent ID: 8542021

Claim:
A fault detection system for a power distribution system having at least first and second line conductors carrying AC currents that are out of phase with each other from a source to a load, and a common neutral conductor, comprising an arcing fault current sensor comprising a coil wound on a hollow core and adapted to be coupled to both of said line conductors in a manner that the electrical currents in said line conductors flow in opposite directions inside said hollow core and thus inducing in said coil a first output signal that is a function of the difference of the electrical currents in said line conductors, a neutral current sensor producing a second output signal representing the magnitude and phase direction of current in said neutral conductor, an arcing fault detection circuit receiving said first output signal and including a processor receiving said first and second output signals and programmed to respond to a change in said first output signal to analyze said second output signal to determine whether said change in said first output signal is attributable at least in part to current in a line-to-line circuit and, if the answer is affirmative, determining a scaling factor to be used to adjust the value of said first output signal, and analyze said adjusted first output signal to determine whether an arcing fault has occurred.