Effect of grading ring on ice characteristics and flashover performance of 220 kVcomposite insulators with different shed configurations

The energized icing tests for five kinds of 220 kV composite insulators with and without the grading ring (GR) at the high voltage (HV) end are performed in the artificial climate chamber. Combining with the numerical simulations of electric field (E-field), the differences between the influence of GR and shed configuration on the ice characteristics and flashover performance of composite insulators are compared and analyzed. Results indicate that GR can improve both the ice growths and E-field distributions near the HV end. The improvements of GR on the icing flashover voltages under light icing degree is relatively obvious, while with the increase of icing degree, these effects gradually become less apparent. For different insulators, the effects of icing degree on icing flashover voltages under the presence of GRs are all higher than that under the absence of GRs. Moreover, the influence law of icing degree among different insulators remains unchanged under the presence and absence of GRs. In general, the improvement of optimized shed configuration for the icing flashover performance is more obvious than that of GR, which can be considered as one main measure to improve insulation performance of composite insulators in ice regions.