Study Of DC Flashover Performance And Mechanism Of A Cylindrical Ice Model And Post Insulators Covered-with Ice

The electrical insulation strength will be reduced obviously as ice accretion on insulators, and power outages caused by insulator flashover as a result of ice accretions have been reported throughout China as well as several other countries. With the large-scale exploitation of power resource in the West of China, the effects of icing on the external insulation of overhead transmission lines will more stand out. Therefore, a systematic study of flashover performance and mechanism of insulators covered-with ice has both a very important academic meaning and an engineering value. By now, a great deal of investigation has been carried out to study the flashover performance of iced or icing insulators, but there have been only a few of research on the flashover mechanism of an iced insulator. So, a cylindrical ice sample and three kinds of real post insulators covered-with ice are carried out DC experimental investigation in the multi-function artificial climate chamber to analyze the flashover performance and mechanism of iced insulators. The main work and conclusion for this paper is as following:(1) Based on the discharge test results of the cylindrical ice model under positive and negative voltage, it is obtained that the electrode shape and the conductivity of freezing-water have much influence on the discharge path of the model. Analyzed the results of DC experiments of the model, the influence of the atmospheric pressure and the conductivity of freezing-water on the values of flashover voltage and the critical flashover current is gained. The lower air pressure is and the higher freezing-water conductivity is, the smaller the values of the flashover voltage and the critical flashover current are.(2) The air gap on stick post insulator coated by ice is used to simulate the air gaps between sheds of iced insulators, the test results show that there is a linear relation between the DC flashover voltage and the length of the air gap. DC+ flashover voltage is lower than DC- on the model surface.(3) The conductivity of freezing-water and the atmospheric pressure have influence on the flashover voltages and critical flashover currents of three kinds of post insulators under heavy icing condition. Under heavy icing condition, the values of the flashover voltages of three kinds of insulators are the same because the lengths of their flashover distances is unanimous, but the sheds figure has influence on the critical flashover currents. There are not polarity effects of the model and under heavy icing condition,whereas it is evident when the air gap exists.(4) Compared the unit flashover voltage between of the ice model and of the stick post insulator covered-with ice, the value of the later is much lower than of the ice model. This is because of the difference of the surface resistances between them.(5) According to the pictures taken by the ultra-high-speed camera, it is observed that the propagation of DC arc on the surface of ZSW1-35-400 post insulator covering-with ice in this paper, the propagated speed of the arc is gained. Meanwhile, the randomicity of the arc way is found, the arc propagates possibly upward or downward.