Influence of moisture and partial discharges on the degradation of high-voltage surge arresters

This paper reports the influence of moisture and internal partial discharges on the degradation of metal oxide varistors in high-voltage surge arresters. Both factors cause an increase in the varistor current under the operating voltage. This phenomenon is dangerous and can cause a total outage of the metal oxide arrester. In the field the moisture ingress can lead to internal discharges. Owing to recovery processes the changes in the voltage-current characteristics of varistors caused by moisture or partial discharges decrease in dry and partial discharge free conditions. The interesting behaviour of some varistors which were degraded by partial discharges was observed. Copyright (C) 2004 John Wiley Sons, Ltd.