Study Of The Characteristics Of Discharge Under DC+ In Icicle To Ice-covered Plane Air Gap

One of the most evident phenomena found for ice accretion on energized insulator is the frequent presence of an air gap near the HV terminal. The existence of air gaps will inevitably distort strongly electrical field distribution and cause to a significant voltage drop across the gap, which causes severely non-uniform electrical field near the icicle top. Electrical field stress at the icicle tips is even stronger. At these areas, if the electric field across air gaps is high enough, corona discharges are initiated. This can lead to the development of local arcs across the air gaps causing a substantial increase in leakage current and a concomitant melting of ice. This phenomenon indicates that there is closed relationship between the development of local arc, the flashover of the insulators and the discharge activity initiated at the icicle tips. So there is important implication value and academic value to systemic investigation of the effect of the existence of air gap to the flashover voltage along the ice-covered insulators.This paper designs the icicle-iced plate model based on the ice-covered insulators and makes an investigation in artificial climate chamber by using CoroCAM IV+ and data acquisition card and so on. By applying related theory of gas discharge and mathematical statistics, this paper more in-depth and systemic study the influence of the length of air gap, ice state, water conductivity and air pressure on the inception corona and pulse discharge characteristics, included the discharge frequency, discharge amplitude and time interval.The results indicate that there is an obvious effect of air gap and ice state on the inception voltage across the air gap. the longer the air gap is, the higher the inception voltage; the inception voltage is lower with 2kV at wet ice than dry ice. While, there is not a distinct effect of water conductivity on the initiative voltage. And the inception voltage decrease with reduction of air pressure (increase of altitude). To the discharge in the air gap, with the increase of applied voltage, the discharge area is larger, and the time interval is smaller, and discharge pulses frequency is higher. While, the mean discharge magnitude increase first and after that it has an approximate constant with the increase of applied voltage. Glow discharge appears when applied voltage further increases. With air gap increases, the mean discharge magnitude reduces. There is not an obvious effect of water conductivity on the mean discharge magnitude at dry ice, however, the mean discharge magnitude increases when water conductivity increases.