The influence of conduction band location on the leakage current level of a glass insulator

Abstract

This paper discusses the influence of conduction band location on the leakage current level of a glass insulator. A sodium chloride solution has been used as a pollutant forming the conduction band. The solution concentration has been changed by using five variations of salt mass which was dissolved into 250 ml of water. The salt mass variation is proportional to its related mole equivalent of sodium chloride solution concentration. The experiment results indicate that the position of the conduction band on the insulator surface affects the surface resistivity. The largest resistivity occurs when the conduction band is located near the ground side, whereas the smallest one occurs when the band is in the middle between the ground side and the HV side. The value of the surface resistance for the band located on the HV side is between that near the ground side and that in the middle location. The level of the leakage current on the glass surface rises with the increase in the applied AC voltage. The leakage current increase is relatively linear up to around 20 kV, beyond which the leakage current starts to decrease. This decrease is related to the formation of dry bands which will increase the overall resistance of the glass insulator surface. The largest power and annual energy losses being caused by the leakage current are found when the conduction band is located in the middle part of the surface, whereas the smallest ones are obtained when the conduction band is located on the ground side. The power and annual energy losses increase even greater when the applied voltage is higher.