Comparison of AC icing flashover performances of 220 kV composite insulators with different shed configurations

The shed configuration has obvious effects on the flow field characteristics and electric field distributions around composite insulators, and then impacts their icing flashover performance. In this study, the AC flashover comparative tests for 12 types of 220 kV composite insulators with different shed configurations under non-energized and energized ice accumulation conditions are conducted in the artificial climate chamber. The influences of shed configuration on icing flashover voltages and flashover arc paths are analyzed. Results indicate that with the increase of the icing stress, both the flashover arc path and the ratio of the air gap arc gradually decrease. These variations lead the icing flashover voltage to gradually decrease and then approach to saturation. For ice-covered composite insulators with different shed configurations, the ratios of the air gap arc to the total flashover arc are different due to the differences of their shed spacings, icicle lengths, differences of shed diameters, (extra) large shed diameters. These result in the differences of icing flashover voltages and their characteristic exponent c describing the influence of ice thickness. Besides, for insulators iced under energized condition, their icing flashover voltages and flashover arc paths are different from that under non-energized condition. Hence, the energized icing test, which is also the only normative reference of icing test proposed by the IEEE standard, should be carried out to optimize the shed configuration of composite insulators used in ice areas.