Study On DC Pollution Flashover Performance Of Composite Insulator With Different Shed Configuration Under Low Air Pressure

The composite insulator is widely used in transmission line for its good performance in contamination flashover characteristics. However, there is an increasing number of pollution flashover accidents occurred on composite insulators for the unreasonable parameter of composite insulator. The shed configuration has a great effect on the flashover performance of composite insulator under high altitude. Therefore, a systematic study on DC Pollution flashover performance of composite insulator with different shed configuration under low air pressure has important academic and engineering practical application values. The analysis of the shed configuration’s effect on the flashover performance of composite insulator and the arc development process is done in this paper. The study’s main conclusions of this paper are as follows:① The average pollution flashover voltage gradient, EL, of composite insulators with big-small shed profile structure is higher than the composite insulators with big-small-small and big-small-medium-small shed profile structure. With the same altitude and contamination level, for the composite insulator with big-small shed profile structure, when the EL is higher, the better CF coefficient、s/p、l/d is 3.11、1.39、3.41, respectively.② The average pollution flashover voltage gradient, EH, of composite insulators with big-small shed profile structure is higher than the composite insulators with big-small-small and big-small-medium-small shed profile structure. With the same altitude and contamination level, for the composite insulator with big-small shed profile structure, when the EH is higher, the better CF coefficient、s/p、l/d is 3.15、1.35、3.44.③ The salt influencing characteristic exponent, a, decreases with the increase of the altitude’s height, and when the altitude changes in the range of 232~4500m, the salt influencing characteristic exponent changes in the range of 0.14~0.28. The salt influencing characteristic exponent decreases with the decrease of the CF coefficient and the l/d. The a also increases with the decrease of the s/p and h.④ The atmospheric influencing characteristic exponent, n, decreases with the increase of salt density. When the salt density changes in the range of 0.05~0.25mg/cm2, the s atmospheric influencing characteristic exponent changes in the range of 0.53~0. 78. With the same salt density and the same shed combination, n decreases with the increase of s/p and h. n also increases with the increase of l/d and CF coefficient.⑤ The proportion of air space arc, k2, increases with the decrease of air pressure by the relationship of power function. When the altitude changes in the range of 232~4500m, the k2 changes in the range of 0.19~0.45. The air space arc proportion’s atmospheric influencing characteristic exponent, m2, is fitted. The analysis of m2 shows the CF coefficient should be moderate on high altitude and contamination area.⑥ In the initial stage, the arc development is slow, and the development speed is between 0~10 m/s. In the final stages of flashover, the arc development speed increases significantly, and the arc development speed reaches the maximum in the time of critical flashover. The maximum arc development speed, v2, increases with the decrease of atmospheric pressure. The difference of v2 constitute a reason for the difference of pollution flashover performance of composite insulator.