Observation of Flashover Process of 33 kV Long-rod Insulator during Artificial Snowstorm

Summary

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 ?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.

Additional informations

Authors

Liang Xidong, Liu Yingyan