The effects of nonstandard lightning voltage waveshapes on the impulse strength of short air gaps

Sphere-sphere, rod-rod and rod-plane air gaps, each 5-cm long, were tested with lightning surges of eight voltage waves of both polarities. The critical breakdown voltage levels of the tested air gaps attained a minimum plateau within a specific range of wavefronts of the lightning surges. Long time delays of breakdown for the fast-front and short time delays for the slow-front waves were observed. These phenomena would significantly affect the insulation coordination of the power apparatus and systems.< >