Electric discharge along post insulating constructions under rain conditions

The authors present results of an investigation of breakdown characteristics and discharge formation pictures along post insulating constructions under rain conditions with positive polarity switching impulses. Based on the discharge process data obtained, the causes of substantial decrease in post insulation electric strength in the rain were analyzed. The most probable cause of considerably decreased post insulation electric strength under rain conditions (approximately by 40%) is substantially redistributed electric field due to a nonuniform active conductivity distribution along the insulator surface. The discharge formation in the rain is due to the leader mechanism and characterized by a great variety of discharge process forms and features. In order to reduce the risk of post insulation electric strength decrease in the rain, it is necessary to use an insulator having a high structural height along the entire construction