Negative Creeping Discharge along Aerial Insulated Wire under Wet Condition

Abstract

The aerial insulated wires are supported by post insulators and binding wires on the reinforced concrete pole. When a lightning flash strikes near by the wires, the overvoltage due to the indirect lightning surge induces to the conductive wire core. The creeping discharge can develop along the wire surface from the free end of the binding wire through post insulator and reinforced concrete pole compound when a flashover occurred at the post insulator and it also leads to damages on the wire such as melting or snapping. It could be occurred under both rainy and thunderstorm condition. In this case, it indicates that the wire surface is stressed by lightning impulse under wet condition. Consequently, it is an important subject to prevent the wire damages and to clarify the characteristics of creeping discharge along the wire surface under dry and wet condition. In the previous studies, we had observed the characteristics of creeping discharge along the wire surface under dry condition. In this study, we examined creeping discharges under both the impulse voltages with various durations of wave front and wet condition on the wire surface. Then, these voltages were applied to the conductive wire core as the inductive lightning surge. The length and phenomena of negative creeping discharge developing along the wire surface were measured using a still camera with an image intensifier. We report the developing characteristics of negative creeping discharge along the wire surface under wet condition.