Degradation analysis of mineral oil in an oil-immersed ZnO-based surge arrester

In this work the degradation of transformer mineral oil in oil-immersed ZnO-based surge arresters has been studied. Three different kinds of ZnO varistors: 1-non-coated, 2-resin-coated and 3-glass-coated, have been used in this study. It can be seen that after long-period high thermal constraints in oil there is a deposited layer on the varistors' surface which call disturb the function of the non-coated varistors. It is also observed that the ZnO varistor and its coating have an influence on degradation of the oil.