Electrical degradation characteristics of Low Voltage Zinc Oxide Varistor subjected to AC Switching Surges

this paper focuses on degradation analysis on electrical properties of low voltage zinc oxide varistors exposed to voltage switching surges. The operation and reliability performance of Zinc oxide (ZnO) varistors is dependent on its electrical, physical properties and the type of stress applied. Electrical power systems and electronic circuits experience various type of surge voltages resulting from lightning surges, switching surges and electrostatic discharges. Each electrical equipment has a dielectric strength which can be damaged if its level of strength is passed. In this work, the electrical properties of commercially low voltage varistors of same electrical properties and size from two different manufactures exposed to AC switching surges are analyzed. The reference voltages, Capacitances, and clamping voltages of samples are measured before and after application of switching surges to analyse degradation. The Pearson correlation is applied to identify the degree of relationship between reference voltage and clamping voltage of samples. The results obtained show that the mean percentage change of reference voltage of over 10-11 % and a 9.19-10.11 % at 17.28 million surges for manufacture A and B respectively. The calculated clamping voltage ratio increased and capacitance decreases after applied surges.