Switching-Impulse Corona Inception and Breakdown of Large High-Voltage Electordes in Air

It has been shown in the past that irregularities on the surface of an electrode reduce the corona-inception voltage and, under certain conditions, the breakdown voltage of the corresponding gaps. Recent work indicates that rain may reduce the breakdown voltage of large sphere-plane gaps to that of rod-plane gaps of the same clearance. In the present study, laws are established according to which surface irregularities of various shapes and sizes reduce the corona-inception surface gradient of large electrodes stressed by positive switching impulses. The conditions are-also determined under which acceleration of corona inception may reduce the breakdown voltage of a gap formed by a large electrode and a plane, to the level of the breakdown voltage of a rod-plane gap of the same clearance.