Research On The Wet-snow Flashover Performance Of Insulators On UHV Transmission Line

In recent years,UHV project rapidly developed in our country,and the snow-covered insulator on UHV transmission line in snowy area were widely concerned.In this paper,five snow flashover test methods were put forward based on the existing ice flashover test methods.Based on the comparison of the advantages and disadvantages of various methods,boosting after preliminary test voltage is determined as the snow flashover test method.Then,in order to study the influence of the factor such as snow and filth to the flashover voltage of snow-covered insulators.The snow flashover test was designed and carried out under four kinds of snow-cover thickness,three kinds of snow density,three kinds of water conductivity and three kinds of contamination severity,which obtained the relationship between various factors and snow flashover voltage.In the end,the recommended snow defense method is put forward based of the research of snow defense method.The results of snow flashover test under different snow thickness and snow density shows that,the smaller the snow cover thickness and the higher the snow density,the higher the percentage of the insulator covered by snow when it flashover,which leads to the decrease of snow flashover voltage.The results of snow flashover test under different water conductivity and contamination severity shows that,the higher the water conductivity and contamination severity,the lower the snow flashover voltage.It is also found tha t the higher the water conductivity and contamination severity,the discharge of the insulator during snow-melting period would be more serious.In addition,the arc is easier to develop from the location where the water conductivity is higher.The research on snow defense method shows that,physical snow defense methods such as alternative unit pattern and assistant sheds can block the snow bridge and increase the valid creepage distance,which leads to the increase of snow flashover voltage.Meanwhile,PRTV and semiconductor glaze were proved to be unable to increase snow flashover voltage.So,physical snow defense methods were recommended to use in snow area.