Study of flashover model on overhead distribution lines

Abstract

SUMMARYWe have carried out analysis of lightning surge on overhead distribution lines by means of EMTP. We made a model for electric breakdown of a 14-m concrete pole with impulse voltage (rise time: 2 µs) applied to the outer surface at the top of the concrete pole. We found that the transient impedance of the breakdown increased linearly before the breakdown and decreased exponentially after the breakdown. The measured voltage and current waveforms correspond to the calculated waveforms by regarding the impedance of the breakdown as resistance. Also we examined the impedance of flashover of an insulator with impulse voltage applied to the lines. The transient impedance of flashover is expressed approximately by the formula: Z(t) = A × exp(-(t -t 0 )/τ) (A = 1500 to 5000, τ = 3 × 10

Relationship between Creeping Discharge along Aerial Insulated Cable and Duration of Wave Front of Inductive Lightning Surge

“…There are only a few reports on the creeping discharge for the lightning surge with various T f , because actual inductive lightning surges usually are simulated by a standard lightning impulse voltage (1.2/50 μs). While a lot of studies of the distribution line due to the direct or inductive lightning stroke have been performed on the protection of lightning damages , studies on the creeping discharges at the cable surface caused by the lightning strike are very few, particularly, the effect of T f on the creeping discharge has not been clarified for the present.…”