Research On AC Flashover Characteristic Of Porcelain Insulator In High Conductivity Fog

In recent years, the occurrence frequency of fog is growing and it’s severity increases continuously in China, especially in urban industrial zone and coastal areas,where appeares high conductivity fog.The average value of fog water conductivity is up to 2000~3000μS/cm, which can exist stably more than 8~10h. Considering the high conductivity and settling property, the impact of high conductivity fog on external insulation of transmission line cannot be ignored. Therefore, this thesis conducts the research on AC Flashover charaeteristic of porcelain insulators in high conductivity fog, which are commonly used in UHV transmission lines.The main contents are shown as follow:(1) Test system has been built and the flashover voltage formula has been corrected. A small-scale artificial climate chamber for insulator flashover test in high conductivity fog was built. Based on the artificial climate chamber, this thesis conducts the flashover test of short-string porcelain insulator,which covered with three different salt density,in clean fog and high conductivity fog. In addition, the flashover voltage formula has been corrected, considering the impact of fog water conductivity.(2) The mechanism research on flashover voltage of short-string porcelain insulator influenced by high conductivity fog has been carried out. By collecting the leakage current of short-string insulator at working voltage in high conductivity fog,this thesis analysis the effects of high conductivity fog on the contamination degree of insulator surface. In addition, the electric field of short-string porcelain insulators has been simulated based on Comsol Multiphysics, and the results show that the electric field through the path of flashover and the junction of different dielectric could be influenced by the fog water conductivity.(3) A method had been proposed for the flashover early-warning of short-string porcelain insulator in high conductivity fog, which is based on high-frequency component of the leakage current. This thesis obtains the power spectrum of insulator leakage current of clinical-flash stage in high conductivity fog based on Matlab, and by analyzing the high frequency amplitude of power spectrum, the flashover warning threshold has been determined.