Switching Surges with Very Long Fronts (above 1500 μs): Effect of Front Shape on Discharge Voltage

The results of dry positive-polarity switching impulse tests on a 4-meter rod-plane gap are reported. The tests were performed using two different shapes for the front of the impulse applied: one shape consisted of the "smooth" front commonly used in switching impulse tests; the second shape was obtained by super- imposing a short "bump" on a very long "smooth" front just before the crest was reached.