Switching-Surge Flashover of EHV-UHV Towers

Design curves are presented for switching-surge flashover of tower window gaps 20 to 39 feet (6.1 to 11.9 meters), bundle conductor-to-ground gaps spaced 20 to 50 feet (6.1 to 15.2 meters), and bundle conductor-to-tower leg gaps spaced 14 to 29 feet (4.3 to 8.8 meters). The critical flashover voltage range is from 1100 to 2700 kV. Together with the above, the following variables were investigated: time to crest, insulator string length, rain, window-shape, tower width, conductor entrance angle, and conductor configuration. In addition, work was accomplished on standard deviation, time to flashover, and flashover patterns.