Effects of dynamic deformation of pendant water drops on the electric field between hollow porcelain insulator sheds under extreme rainfall

Abstract

Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall. This study aims to investigate the spatial and temporal variation of electric fields between hollow porcelain insulator sheds affected by dynamic deformation of pendant water drops and effects of the dimensionless number of fluids, the Weber number (We) and the electric Bond number (BoE), on it for influencing factors' analysis. Flow-electric field coupling simulations were carried out to compute the magnitude and the position of AC electric fields between the sheds. The results show that the maximum electric field at a point in time (Etmax) increases significantly after the breakup of the pendant water drop, and its position alters accordingly. For low We and BoE, the global maximum electric field (Egmax) increases with increasing We and BoE, respectively. It is much closer to the adjacent sheds and occurs later than Etmax at the breakup of the pendant water drop (Ebmax). By contrast, Egmax decreases in different degrees at high We and BoE, respectively. There is little difference between Egmax and Ebmax in the position and the occurring time. The influence mechanism on the maximum electric field and discharges and the relationship between discharges induced by the pendant water drop and rain flashover are discussed.