METHOD AND APPARATUS FOR DETECTING AND SUPPRESSING A PARALLEL ARC FAULT

Electrical equipment is safeguarded from damage due to parallel arc faults by a circuit that provides several levels of protection. A semiconductor switch and a current sensor are placed in series with the electrical equipment. When the current to the equipment exceeds a first threshold for a predefined period of time, the semiconductor switch is rendered non-conductive until the circuit is specifically reset. When the current to the equipment exceeds a greater second threshold, a pulsed signal alternately places the semiconductor switch in conductive and non- conductive states so that the average current applied to the equipment is within an acceptable level. The pulses are measured to determine whether a parallel arc fault has occurred. When the measured pulses are within a predetermined range, a parallel arc fault is declared and the semiconductor switch is rendered non-conductive. Should the current exceed an even greater third threshold, the semiconductor switch is immediately rendered non-conductive until the circuit is manually reset.