Multi-pole arcing fault circuit breaker including a neutral current sensor

Abstract

A fault detection system is provided 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. The system includes an arcing fault current sensor comprising a coil wound on a hollow core and coupled to both of the line conductors in a manner that the electrical currents in the line conductors flow in opposite directions inside the hollow core, thus inducing in the coil an output signal that is a function of the difference of the electrical currents in the line conductors. A neutral current sensor produces an output signal representing the magnitude and phase direction of current in the neutral conductor. An arcing fault detection circuit includes a processor programmed to (1) respond to a change in the first output signal to analyze the second output signal to determine whether the change in the first output signal is attributable at least in part to current in a line-to-line circuit, (2) if the answer is affirmative, determine a scaling factor to be used to adjust the value of the first output signal, and (3) analyze the adjusted first output signal to determine whether an arcing fault has occurred and produce a trip signal in response to the detection of an arcing fault.