The energy absorption capability and time-to-failure of varistors used in station-class metal-oxide surge arresters

Varistors for use in station-class surge arresters were tested to destruction to determine their energy absorption capability at current levels ranging from 0.8 Apeak to 35 kA,,,k. Typical mean values increased from 400-600 J/cm3 at the lower current end to 1,600-2,000 J/cm3 at 35 kApeak. The product of the mean time-to-failure and the mean current was found to be a constant over five orders of magnitude. The varistor failure mode was found to be a characteristic of the current magnitude. It is recommended that standard test methods be developed for the energy absorption capability of metal-oxide surge arresters, and be included ih relevant standards.