Abstract: A portable tester plugs into a receptacle in a branch circuit of an electric power distribution system to verify protection against arc faults, line to ground faults and neutral to ground faults provided by a circuit breaker located at a remote load center or by ground fault and, or arc fault interrupters in the receptacle, and also checks for proper wiring. The arc fault detector gates phased back rectified half cycles of the ac power to generate step changes in the instantaneous amplitude of current in the branch circuit which mimic the repetitive striking of an arc. Preferably, only half cycles at least 60 ms apart are gated so that the user can verify the time to trip with a watch and can count the gated half cycles to trip by counting pulses generated by a light emitting diode (LED) in the gating circuit.

Abstract: A test circuit for arc fault detectors of the type which respond to step changes in ac current over time generated each time an arc is struck includes a low frequency relaxation oscillator which generates a repetitive signal with step changes like those produced by an arc fault. The relaxation oscillator includes a capacitor charged through a resistor and shunted by a voltage breakdown device, preferably a diac. The capacitor is rapidly discharged when its voltage reaches the breakdown voltage of the voltage breakdown device to generate the step change which is input to the arc fault detector. With a repetition rate of the relaxation oscillator not greater than about 15 repetitions per second (rps), and preferably about 5 rps, a user can manually determine the time to trip to verify arc fault detector operation.

Abstract: An arc fault detector having a pulse generator generating a pulse each time an arc is struck includes a limiting amplifier which limits the amplitude of the pulses to discriminate against false trips from sizable singular events such as tungsten bulb burnout and turn-on of a cold tungsten lamp controlled by a phased back dimmer. When a time attenuated accumulation of the pulses reaches a predetermined level an arc fault signal which can be used to trip the circuit breaker is generated. The pulse generator of the arc fault detector includes multiple stages of high pass filtering which produces overshoot and therefore additional pulses each time an arc is struck. As only the additional pulses associated with large amplitude arcs exceed a threshold value for inclusion in the time attenuated accumulation, compensation for the reduction in sensitivity to large amplitude arcs imposed by the limiting amplitude is provided.

Abstract: Arcing faults are detected by a multi-channel arc fault detector in which each channel includes a bandpass filter having an assigned discrete passband which is non-overlapping with the passband of any of the other bandpass filters. Thus, the detector can discriminate an arcing fault which produces white noise and therefore generates an output from all of the bandpass filters simultaneously from a carrier signal which will only produce an output from one bandpass filter. The output of the individual bandpass filters can be ANDed, for example, by comparators with a common pull up resistor, or by analog multipliers. The output of the arcing fault detector can be used to trip a circuit breaker.