Study on AC Flashover Process of Iced 110 kV Insulator Strings

As a result of the freezing weather,many 110 kV or higher voltage power lines tripped due to icing in the north of Guangdong Province,such as in Qingyuan and Shaoguan.In order to understand ice flashover performance on insulator strings,the ice flashover process on 110 kV insulator strings was investigate.Taking into account the icing feature of insulator strings in the north area of Guangdong Province,uniform ice layer on both top and bottom surfaces of an insulator was simulated in CEPRI(China Electric Power Research Institute) Artificial Weather Laboratory.More attention was paid to the effect of icicle length on the ice flashover process.And the influences of thawy ice water's conductivity and pollution degree of the insulator on the ice flashover process during ice thawing period were also investigated.The results show that: salt-precipitation in thawy ice water on the surface of insulator significantly increases the conductivity of melting ice to reduce the flashover voltage of the iced insulator string;the ice flashover process of iced insulator string without icicles is similar to that of pollution flashover,while the path of flashover is along the un-bridged icicles with the presence of icicles;pollution leads to more serious flashover.