Effect of humidity on the properties of corona in a rod—plane gap under positive impulse voltages

Abstract

An experimental survey has been made of the effects of humidity on several properties of the positive corona discharge formed during 1/50 μs impulses in the region of the withstand voltage of a 60 cm rod-plane gap. By using field and charge measurement techniques simultaneously with direct photography and measurements of inception voltage, the variations with humidity of net corona charge and charge density, corona ‘radius’, electric field for propagation and charge transfer at the plane cathode have been characterized. It is shown that a number of these parameters change with humidity at about the same rate as the withstand voltage, that is, of the order of 1%/(g m -3 ), though the variation in net charge is an order of magnitude greater. Interaction with the cathode is discussed and shown to be complicated by the changes in the nature of corona that occur at higher humidities.