Aging Of Overvoltage Protection Elements Caused By Past Activations

Abstract

This paper investigates the ageing process of some common elements used for overvoltage protection. Tested elements are overvoltage diodes, varistors and gas filled surge arresters. Ageing process is considered as a function of previous number of element activations. Experiments are performed both with voltage and current transients. Statistical analysis of experimental data has shown that all elements investigated are subjected to the ageing during their functional operation. After 1000 overvotage diode activations, the volt-ampere characteristic curve "breaking" has been noticed in the range of higher currents, while the breakdown voltage value is reduced. In the case of varistor, it is determined that with higher number of activations comes an increase in the value of breakdown voltage and the shift of volt-ampere characteristics in the field of higher voltage. As for the aging of gas filled surge arresters, it has been shown that past activations reduce the value of dc breakdown voltage and lead to narrowing the area bounded by the 0.1% and 99.9% quintiles of the impulse characteristics.