ARC FAULT DETECTOR COMPARING INTEGRATED INTERVAL TO INTERVAL FILTERED LOAD CURRENT AND CIRCUIT BREAKER INCORPORATING SAME

Arc faults are detected by bandpass filtering the current to generate a sensed current signal with a pulse each time an arc is struck. A resettable integrator integrates this sensed current repetitively over equal time intervals such as each cycle of the ac current. The integrated value of the sensed current is compared with the value for the previous corresponding time interval stored in a sample and hold circuit, with the indications of interval to interval increases and decreases in the integrated sensed values for a selected number, such as six, of the most recent time intervals stored in a shift register. For each time interval, a chaos detector counts the number of changes between increases and decreases for the selected number of most recent corresponding time intervals and accumulates a weighted sum of the counts which is time attenuated. When the sum reaches a predetermined amount, an output such as a trip signal for a circuit breaker is generated.