Study On Icing And Flashover Performance For Composite Insulators Of Different Shed Configuration Under Two Pollution Methods

The flashover of iced insulator, which is significantly affected by both shed configuration and pollution degree, is a great threat to the safe operation of transmission line. Researches on shed configuration are mainly focused on composite insulators that designed to work below 110 k V while the difference between energized icing and nonenergized icing is rarely considered. Moreover, the difference among influence rule of shed configuration that under different icing pollution simulation method is always ignored. Therefore, it’s of great significance to investigate the study on icing and flashover performance for composite insulators of different shed configuration under two pollution methods. This study has both academic and practical engineering value to the choice of pollution simulation method for composite insulators in icing region, and the optimization design of shed configuration.220 k V composite insulators of six different shed configurations are applied as test examples in this article. Inside the Artificial Climate Chamber, those insulators are prepolluted by means of solid-layer method(SLM) and icing-water-conductivity method(IWCM) in order to carry out comparative study between energized icing and nonenergized icing. Combining with the monitoring of leakage current during the icing process, the measure of ice layer melted-water conductivity and dripping water conductivity when fashover and the filming of flashover path, the influences of shed configuration and polluting methods on icing and flashover performance of composite insulators are deeply analyzed. Main results are as follows:① By using IWCM, the conductivity of ice layer melted-water and dripping water conductivity when fashover under energized icing condition is lower than that of nonenergized icing condition while SLM does the opposite. Under energized icing condition of IWCM, the icing flashover voltage is higher than that of non-energized condition. And the improved insulator of SLM does the same while normal insulator does the opposite. Moreover, the voltage difference decreases along with the increment of pollution degree.② For composite insulators of different shed configuration, both leakage current amplitude and pulse amplitude and numbers are different. But for composite insulators of same shed configuration, the leakage current amplitude and pulse amplitude under SLM condition are greater than that of IWCM condition at the beginning of icing.③ The difference of flashover path and the ratio of ice arc and air gap arc of flashover is the main reason that causes the difference of icing flashover voltage. Flashover arc is more likely to find minimum leakage path along with shed circle or shed surface.④ Larger values of k1(the ratio of shed spread), k2(the ratio of shed spacing and shed spread) and small value of k3(the ratio of creepage distance of one shed unit and the sum of shed spacings of this unit) is beneficial to the increment of icing flashover voltage, but the C.F.(creepage fanctor) coefficient has no significant relation with icing flashover voltage. Bigger diameter and separation distance of big shed are the key to improve the flashover performance of composite insulators along with shed diameter ratio and appropriate combination of sheds.⑤ Equivalence relation of two pollution methods is power function, and it’s related to energized icing or not, when the Salt Deposit Density(SDD) are the same, the equivalent value of γ20 under energized condition is higher than that under non-energized condition; Under energized icing condition, the equivalence relation of two pollution methods varies with the change of shed configuration, but equivalence relation nearly stays the same under non-energized condition.⑥ The influence index of pollution of composite insulators are related with shed configuration, pollution methods and electric field. Under energized icing condition, the influence of shed configuration upon icing flashover voltage changes with the choice of pollution method. Therefore, in order to analyze shed configuration, pollution methods and energized icing or not are going to be determined in the first place.