Influence of air gaps on the DC withstand voltage of ice-covered UHV insulators

The influence of the number and position of air gaps on the maximum withstand voltage of a typical 735-kV ice-covered station post insulator under DC voltage was investigated both experimentally and numerically. Numerical results obtained by the Finite Element Method (FEM) with the presence of a water film on the ice surface showed that the number of air gaps has a direct effect on the distribution of potential along the iced insulator. Moreover, experimental results showed that the number and position of air gaps have a significant effect on the maximum withstand voltage of ice-covered insulators. In the same way, for the three air gap configurations tested in this study, the maximum withstand voltages obtained showed the lowest value when two of the air gaps are located at the top and bottom of the insulator. The results obtained will be helpful in the design of HVDC insulators in regions subjected to atmospheric icing.