AC power disturbance detector circuit

The authors describe the design, construction, and performance of a circuit that detects transient disturbances on low-voltage AC supply mains. Such disturbances include reactive loads, large departures from the nominal RMS voltage, severe harmonic distortion, and outages. While this circuit was designed for use on single-phase mains, the primary side of the isolation transformer could be connected between one three-phase line and neutral. The disturbance detector circuit can be used to trigger a digital waveform recorder, as in the present application, or to operate a counter circuit to simply record the occurrence of a disturbance