Effects of environmental factors on the ageing monitoring of gapless surge arresters

Abstract

The gapless metal oxide surge arresters (MOSA) have been available in the market for many years since they were first introduced in the 1970’s. Its primary function is to protect the equipment in the system against various electrical overstresses. They are widely used for lightning protection of power system equipment. A reliable condition monitoring of zinc oxide surge arrester is vital to its performance to ensure the continuity and reliability of power supply. It is known that voltage-current characteristics of zinc oxide varistors become degraded due to a series of stresses. Leakage current of the surge arrester can be increased by some environmental factors. This fact has a significant effect on the arrester performance resulting in the eventual failure of the surge arrester. The aim of this study is to investigate the effects of different environmental factors such as moisture, temperature and etcetera on the ageing mechanism of the gapless surge arrester using COMSOL software. A 10kA, 120kV rated gapless zinc oxide surge arrester was modeled in the software using actual dimensions. The different environmental factors such as moisture and temperature are modelled and simulated in the software. Finally the simulation results are compared with the available experimental data. The results show that the ageing of the gapless zinc oxide surge arrester is dependent on its internal temperature, surface temperature and leakage current. This is to say that there is a relationship between the arrester’s surface temperature and leakage current. The surface temperature increases as the ageing increases. Ageing can be simulated by either the increase in leakage current artificially or changing the material properties. Apart from ambient temperature and leakage current, other environmental factors also affect the surge arrester surface temperature