Developing Process of Positive Creeping Discharge along Aerial Insulated Wire

Abstract

In high voltage aerial distribution systems, the insulated wires are supported by the insulator with the binding wire at the electric light pole. When a lightning strike happened in the neighborhood of the aerial insulated wire in a power distribution system, the inductive lightning surges invade to the central line of the wire. Then, the creeping discharges develop along the wire surface from the binding wire tip in the same time as the flashover of the insulator at a supporting point of the wire. If the wire insulator has weak points such as the pin-holes, the disaster near the wire supporting point may occur with a melting of wire due to the punch-through breakdown. To prevent such accidents, it is important to clarify the mechanism of the creeping discharge along the insulated wire which caused by the lightning strike. The polarity of creeping discharges is decided by the polarity of inductive lightning surges, and the developing length and aspect of the discharge are greatly different by the discharge polarity. The developing of these creeping discharges is attributed to complicated behaviors of the positive and negative electric charges.In the present study, we examined in detail the developing process of positive creeping discharge along the wire surface by using a high speed image converter camera. This paper describes the developing mechanism of positive creeping discharge based on the experimental results.