Influence of corona discharges on the breakdown voltage of airgaps

Measurements with rod-rod and rod-plane gaps result in a large scatter in the values of breakdown voltage at certain gap distances. The scatter in the figures depends on the change of the corona mode. The transition in predischarges at certain gap distances results in two different breakdown voltages. It is shown that this scatter can be observed with all investigated voltage shapes (alternating and direct voltages, lightning and switching surges). The paper also deals with the possibilities of influencing the scatter of the values of breakdown voltage.