Flashover performance of EHV station post insulators covered with ice

The icing performance of standard-shed-design porcelain insulators, with a dry arcing distance of up to 4.17 m, corresponding to full-scale Hydro-Quebec 735 kV substation insulators, was investigated. Artificial ice was formed at -12/spl deg/C in a climate room from supercooled water droplets produced by a set of pneumatic nozzles. The relationship between the maximum withstand voltage, V/sub WS/, and insulator length was determined. With an applied water conductivity of 30 /spl mu/S/cm and an ice thickness of 15 mm, measured on a rotating monitoring cylinder, flashover may occur at service voltage. Moreover, the V/sub WS/ of the ice-covered insulators tested increases non-linearly with an increase in insulator length. These results are of great importance for the design of EHV substation insulators used in cold climate regions.