Modelling of flashover performance of an ice-covered resistive glazed post station insulator in presence of an air gap

The main objective of this paper is to study the electric field distributions around a standard post insulator for the power frequency, lightning impulse (1.2/50 μs) and switching impulse (250/2500 μs) voltages under icing conditions, and these were computed numerically using the finite element method. Thin glaze coating on the insulator requires a very large number of elements for finite element analysis because of the open boundary around the ice-covered insulator. To reduce the number of elements and hence computation time, the region between the domain of interest and infinity was modelled by a form of Kelvin transformation. The simulation results, confirmed by laboratory experiments, show that while a lightning impulse is the limiting factor in the design of a resistive glazed insulator under clean conditions, a switching impulse is the limiting factor under icing conditions