The Front Shape of Switching Impulses and its Effect on Breakdown Parameters

A 3-meter rod-plane gap was tested with double exponential switching impulses of different front times. The front of each of the impulses was subsequently modified so that it rose steeply to a certain level of the original front and then followed the basic non-modified impulse. This front modification made it possible to study the influence each region of the front has on the 50% breakdown voltage and the standard deviation of air-gaps. From the results obtained it was possible to detect the region of the front which mainly affects the breakdown parameters. Based on these results, a new definition of the switching-impulse front is proposed providing concrete information about the response of a gap when subjected to an impulse with a given front.