This standard applies to varistors for surge protective applications on systems with dc to 420 Hz frequency and voltages equal to or less than 1000 V rms, or 1200 V dc. This standard contains definitions, service conditions and a series of test criteria for determining the electrical characteristics of these varistors. If the characteristics differ with the direction of conduction, then the tests determine characteristics for both polarities. Arresters covered by ANSI/IEEE C62.1-1984 [1] are excluded from this standard.