Patent ID: 7333920

Claim:
An arc fault detecting device capable of being electrically connected to an electrical wiring system between line side phase and neutral conductors and load side phase and neutral conductors, said device comprising: signal detecting means coupled to detect current in a conductor of the electrical wiring system to generate a signal representative of the detected current, signal modifying means coupled to the signal detecting means to generate a CURRENT signal which represents the filtered or unfiltered current detected in the conductor, and a micro-controller coupled to receive the generated CURRENT signal wherein the micro-controller performs the following: generates a SINE signal having half cycles and zero crossings from a raw input signal, or a signal from a finite impulse response (FIR) filter, or a signal from an infinite impulse response (IIR) filter and, when generating the SINE signal, locates a starting CURRENT zero crossing, finds the average of following half cycles of the CURRENT signal, finds a peak of the same polarity as the average in that half cycle, multiplies the peak height by the CURRENT at that point, assumes that real zero crossings are exactly 1/240 second on either side of the peak, and lockouts ¼ cycle from the leading zero crossing when advancing to next zero crossing, subtracts the CURRENT signal from the generated SINE signal and divides the result by the SINE signal to obtain a DELTA signal, analyzes the DELTA signal for at least one characteristic representative of the occurrence of an arc, and generates an output signal upon detection of the at least one characteristic representative of the occurrence of an arc.