DC positive discharge performance of rod-plane short air gap under rain conditions

To study the discharge performance of air gap under rain conditions and provide reference to the selection of clearance distance of external insulation in strong rain, this paper explored the influence of different environment conditions, rain intensity, rain conductivity, and ambient temperature on the dc positive breakdown voltage of rodplane air gap in the artificial climate chamber and at Xuefeng Mountain Natural Site. It is shown that the discharge voltage of rod-plane short air gap in wet condition is slightly higher than that in the dry condition; light rain has little influence on the positive dc discharge voltage of rod-plane short air gap. The relative discharge voltage of air gap decreases with an increase of rain intensity and rain conductivity with 2.2% to 0.2% / (mm/min), 1.4% to 0.1% / (100 μS/cm), respetively; and it is associated with the increase of ambient temperature with 0.3% to 0.1% / °C. In addition, several computations were carried out with different droplet sizes in rod-plane air gap. It can be indicated that the maximum electric field in the air gap increases with the increase of the radius and number of droplets.