Influence of Critical Working Conditions on Stability of Varistor Characteristics

In this paper, the results of the analysis of the influence of critical working conditions on stability of varistor characteristics are presented. Moreover, the paper offers both experimental and theoretical interpretation concerning the influence of temperature, operations’ time-number and the effect of neutron and gamma radiation on the stability of varistor characteristics. For the purpose of this paper an original measuring system of extremely low measurement uncertainty has been developed. Recording of volt-ampere, volt-ohm characteristics as well as varistor, breakdown voltage which was directly measured by a measuring system developed for that purpose, was carried out in the manner based on utilizing a single current pulse. Having analyzed the obtained results, it can be concluded that, when designing the insulation coordination at low or high voltage level, ambient environmental conditions (temperature variation) and functional aging in synergy with natural aging should be taken into account.