Effect of Humidity on Corona Characteristics Under Rod-Plane Gap

Abstract

Corona is one of the important problems in the design and operation of transmission lines, and humidity has a significant effect on the starting voltage of the wire corona. The paper focuses on the development of positive DC corona under different humidity conditions, including the corona onset voltage, corona streamer pulse characteristics and the conversion process of streamer corona to glow corona. The paper arrives the conclusion that when a positive DC voltage is applied, a pre-initial streamer occurs first as the voltage increases, followed by glow corona. When the voltage is further increased and the ratio of the rod electrode radius to the gap distance is less than a certain value, the breakdown occurs directly. If the ratio is greater than a certain value, a pre-breakdown streamer will occur before the glow corona when the voltage rises. In addition, the corona onset voltage increases with the rise of humidity, which is related to the absorption of electrons in the electric field by water molecules. Under low humidity, there is a pulsed streamer discharge in the narrow voltage range, but under high humidity, there is always a streamer discharge in a wider voltage range. This shows that as the humidity increases, the streamer corona is more difficult to convert into a glow corona.