Development of a positive creeping discharge along an aerial insulated wire

Abstract

SUMMARYIn high-voltage aerial distribution systems, the insulated cables are supported by the binding wire with the post insulator at the utility pole. When a lightning strike occurs in the neighborhood of the insulated cable in an aerial power distribution system, inductive lightning surges invade the central line of the cable. Then, creeping discharges develop along the cable surface from the binding wire tip at the same time as flashover of the post insulator at a supporting point of the cable. If the cable insulator has weak points such as pinholes, a malfunction near the cable supporting point may occur, with melting of the wire due to punch-through breakdown. To prevent such accidents, it is important to clarify the mechanism of the creeping discharge along the insulated cable caused by the lightning strike. The polarity of creeping discharges depends on the polarity of the inductive lightning surges, and the extension length and aspect of the discharge differ greatly depending on the discharge polarity. The development of these creeping discharges is attributed to complicated behavior of the positive and negative electric charges.In the present study, we examined in detail the development of a positive creeping discharge along a wire surface by using a high-speed image converter camera. This paper describes the mechanism of development of a positive creeping discharge based on the experimental results.

Negative Creeping Discharge along Aerial Insulated Wire in Wet Condition

“…However, the development of creeping discharges is affected by various factors, such as the wave front duration of the lightning surge, its peak value, the wire surface conditions, and so on. In particular, we have discussed the effects of the wave front duration and peak value elsewhere [3][4][5][6][7][8][9][10][11][12], but the influence of wire surface conditions remains unclear.…”

“…We studied the development of creeping discharges along an aerial wire surface under dry conditions in a laboratory environment using impulse lightning voltages with different wave front durations (T f ) [3][4][5][6][7][8][9][10][11][12]. We also observed creeping discharges under wet conditions with water drops present on the conductor surface, representing an after-rain state, using a standard lightning impulse voltage to simulate a lightning-induced surge [3].…”