Numerical analysis of the combined effects of booster sheds and grading rings on an ice-covered EHV ceramic post insulator

In this paper, preliminary results of numerical investigations concerning the combined effect of Booster Sheds (BSs) and Grading Rings (GRs) on the wet-grown ice accumulation on two units of an EHV post station insulator are presented. Numerical simulations were carried out using the finite element method (FEM) to calculate the voltage drop distributions along different air gap configurations. In particular, it was shown that following the addition of 4, 5 or 6 booster sheds with or without grading rings, 42 to 54% of the applied voltage was dropped along the closest air gap to the HV electrode, which was also the longest one. Moreover, it was found that adding different grading rings leads to a decrease in the voltage drops along the first air gap formed by the booster sheds during the ice accretion, resulting in more uniform potential distributions. Finally, based on previous experiments carried out at CIGELE and these new numerical simulation studies, the combined effect of booster sheds and grading rings for improving the electrical performance of EHV post insulators under heavy icing conditions, was discussed.