Switching Surge Tests on Simulated and Full-Scale EHV Tower-Insulator Systems

Switching surge tests performed on simulated tower-insulator systems representative of possible 345- and 500-kV transmission line designs were performed so that line design parameters could be estimated for a specific value of switching surge overvoltage. Switching surge studies of the Southern California Edison Company (SCE) 500-kV transmission system dictated that the switching surge withstand strength for wet conditions should be 1065 kV. From the design-application curves, the center phase of the SCE 500-kV transmission tower-insulator system was designed to have a 12-foot 8-inch minimum horizontal strike distance and 27 insulators used in a 90-degree V-string configuration. Full-scale tower tests confirmed the switching surge design criteria.