Modeling of the AC Arc Discharge on Snow-covered Insulators
ABSTRACT A mathematical model for predicting the ac flashover voltage of snow-covered insulators is presented. The arc constant parameters in air gaps and inside snow, as well as the arc reignition condition are determined using a cylindrical model. The effects of the arc length on the arc constants parameters are also investigated. The model is then applied to an EPDM insulator artificially covered with natural snow. There is good concordance between the flashover results determined from the mathematical model and those obtained experimentally.
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- "The phenomena recorded during the disaster had not been encountered before and were quite different from the ones seen on the so-called snow-covered or snow-capped insulators       . "
ABSTRACT: This paper presents the AC flashover process of a snow-bridged long-rod insulator used for 33 kV overhead lines in the presence of a salt contaminated snowstorm in a climatic chamber. The severity of the snowstorm was defined as having snow conductivity up to approximately 1,000 micro S/cm, 10 m/s of wind velocity, and 9.2 g/m3 of mass density of drifting snow. Leakage current waveforms under constant voltage stress were monitored. Visual observations of discharge propagation were also carried out by using a high-speed camera simultaneously with the leakage current measurement. The results showed that a spark-like partial discharge appeared at the snow gaps during the initial cycle of sequent current waves before flashover. Then the spark-like discharge bridged a gap between the insulator sheds and transferred to partial arc discharges. After the transition, partial arc discharges expanded and contracted along with the instantaneous electrical stress. When these were seen in the same phase angle as the power frequency, the partial arc discharges gradually propagated over the surface of the snow on the specimen until they were combined between both sides of the electrodes to reach flashover. The flashover processes were mostly same, even for various snow conditions. This process was always initiated at the snow gaps. Therefore, it was suggested that the appearances of snow gaps played an important role in the flashover process of a snow-bridged long-rod insulator.19th International Symposium on High Voltage Engineering – ISH 2015, Pilsen, Czech Republic; 08/2015
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ABSTRACT: Due to the wide application of composite insulators in the power industry, the insulator performance is challenged by various environments. To determine the flashover performance of rime-iced composite insulator, laboratory investigation was carried out in an artificial climate chamber to simulate different rime-ice morphology on the insulator surface. The configuration and characteristics of the rime-ice were demonstrated to establish the relationship between the rime-ice parameters and the flashover performance. In accordance with the discharge phenomena, the transition of leakage current (LC) until the flashover was analyzed by using a recurrent plot approach. After extracting the high frequency components by using a wavelet transform technique, the LC just before the flashover was extended to m dimensional phase space based on a phase space reconstructed method. The recurrent plot was obtained to reveal the non-linear characteristics of LC for identifying the dynamic behaviors on the insulator surface. It is shown that the propagation and properties of the discharges can be graphically projected on the topological structure of recurrent plot as a function of the rime-ice parameters. The process and underlying mechanism of flashover performance of rime-iced composite insulator can be visually reflected by the recurrent plot and the quantitative indicators of LC.IEEE Transactions on Dielectrics and Electrical Insulation 05/2010; DOI:10.1109/TDEI.2010.5448102 · 1.23 Impact Factor