| The pollution flashover accidents of composite insulators caused by cement often happened under the humidification environment.It is of great importance for studying the influence of cement pollution on hydrophobicity of composite insulator and the mechanism of pollution flashover in order to keep the safety in operation.First of all,the phenomenon of hydrophobicity transfer on composite insulator has been studied in this paper.The experimental result shows that the hydrophobicity transfer of cement is weaker than kieselguhr,and better than kaolin;the influence of hydrophobicity transfer on cement is caused by the microstructure of cement,not by the components of cement.Due to the range of NSDD of composite insulators near the cement mills is quite wide,the effect of different NSDD has been studied in this paper. The experimental result shows that the relationship between flashover voltage and NSDD is Uf= AÏNSDD-b.Moreover,the flashover voltage increases as the hydrophobicity enhances in the same NSDD.The experiments of hydrophobicity transfer and pollution flashover on the cement whose thickness is 2mm were put up.The experimental result shows that there is no hydrophobicity on the surface of cement pollution;the average voltage of the first flashover on the hydrophilic samples is 21kv,which is similar to the hydrophilic samples whose NSDD is 2 mg/cm2.The author analyzes that it is probably as the cement pollution is quite thick,LMW can't transfer to the surface of the cement pollution,so there is no water droplet on the surface of the cement pollution,and the state that there is no water droplet on the surface of the cement pollution increases the surface resistance,the partial electric arc is restrained,so the pollution flashover voltage is high.Further work should be taken to study the mechanism of pollution flashover about composite insulators on the thickness of cement pollution. |
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