AC breakdown performance and voltage correction of rod-plane short air gap under rain conditions

According to the operation experience and investigation in China, the insulation performance of transmission line can be reduced due to the effect of strong rain, which is not considered in the external insulation design. Meanwhile, there is no correction reference regarding the breakdown voltage of air gap under rain conditions in IEC standards. Therefore, a series of experimental tests were conducted in the artificial climate chamber and at Xuefeng Mountain Natural Site with the usage of rod-plane air gap to analyze the relationship between ac breakdown voltage and rain precipitation rate, rain conductivity and ambient temperature. It is shown that the breakdown voltage of air gap decreases with an increase of rain precipitation rate and rain conductivity, and increases with an increase of ambient temperature. In addition, according to the test results, the correction formula of ac breakdown voltage of rod-plane air gap under rain condition is proposed and verified in this paper.