Discharge development process and flashover performance of snow-accreted insulators under natural environment

Abstract

The safe and reliable operation of power system in China is significantly affected by snow-covered insulator. At present, many studies on snow-accreted insulator have been undertaken by domestic and foreign scholars in the laboratory. However, whether the laboratory test is equivalent to the field test and whether it can be directly used to guide the external insulation design of transmission line still need to be evaluated. In this regard, AC flashover test of snow-coated insulator was carried out in the laboratory and field in this paper, and then the characteristics of AC discharge path and the variation of leakage current of snow-accreted insulator with time were obtained, and its flashover performance was compared and analysed. The research results show that the amount of snow on the insulator gradually decreases from the stagnation point at the edge of the shed on the windward side to both sides, which is attributed to the uneven distribution of the local collision coefficient of snow crystal particles on the insulator surface. The arc is yellow during the flashover of snow-accreted insulator in the artificial climate chamber. While in the natural environment, the discharge arc appears blue and purple, and the phenomenon of arc levitation and snow layer shedding can be observed. For composite insulator FXBW-35/70 covered with different degrees of snowing in the natural environment, the flashover path develops along the creepage distance in case of the slight snowing, while the path propagates over the dry arc distance under severe snowing condition. Consequently, the flashover voltage decreases by 48.7%. There are many discrepancies between different types of the insulators, such as the creepage distance, dry arc distance and other structural parameters, and the number of air gap after snowing, which affect arc dynamic development properties. Hence, the electrical performance of composite insulator is better than that of glass insulator, and the snowing flashover voltage of the former is 5.56–9.47% higher than that of the latter.