How the switching-surge family affects line insulation

Full-scale switching-surge flashover tests were made at an outdoor laboratory that covered a range of V-string and vertical insulator string lengths, tower sizes, and waveshapes. The response of line insulation to these surges was explored. Effects of precipitation and preceding trapped charge (bias voltage) were investigated, along with rod-to-ground and conductor-to-ground flashover. Estimated performance curves of EHV transmission line structures indicate economic justification for switching-surge limiting apparatus.