AC flashover performance of porcelain, glass and polymeric insulators at high altitudes

With the development of EHV and UHV transmission technology, more and more transmission lines are built across high altitude regions in China. The pollution flashover performances in high altitude regions are affected not only by the pollutants but also by the atmospheric parameters. To study the performance of insulators at high altitudes, six commonly used porcelain, glass and polymer insulators were tested in three high altitude sites with altitudes of 2820, 3575 and 4484m. In this paper, the AC pollution flashover performance of these insulators were modeled and computed at high altitudes, taking into account of the ESDD, NSDD, the pressure and temperature. Further, the respective influences of ESDD, NSDD, air pressure and ambient temperature on flashover voltage gradient were analyzed. The results indicate that polymer insulators have 48.72% higher flashover voltage gradient than porcelain and 72.35% higher than glass insulators at 59kPa (corresponding to 4484m). These results will help to select the type and number of insulators in the high altitude regions.