US Patent 10468875 Varistor failure detector and method

A varistor failure detector includes one or more surge detector in communication with a varistor, to detect surges shunted by the varistor and a processor, in communication with the at surge detector(s). The processor is programmed to count surges shunted by the varistor, as indicated by the surge detector(s) and store at least one count representing a cumulative count of surges shunted by the varistor. An indicator of the count may be provided to an operator to indicate that the varistor should be replaced, to avoid catastrophic failure of the varistor.