Influence mechanism of AC electric field on rime ice accretion on the insulator and its experimental verification in the natural environment

Insulator icing can easily trigger flashover trips in heavily ice-covered areas, and analyzing the formation mechanism of ice accumulation on the insulator is essential for predicting its flashover development. To accurately dissect the process of insulator icing, a coupled mathematical model of the flow field and electric field, as well as a droplet motion model were elaborated in this paper based on the principles of fluid mechanics and electromagnetic field. Subsequently, the characteristics of droplet motion deviation and its physical collision process with an insulator surface under AC electric field were investigated. The results demonstrate that the charged droplets tend to oscillate along the electric field lines in AC electric field, and the amplitude of the oscillation increases with the applied voltage increasing. Moreover, the number of droplets captured by the insulator rises with the increase of voltage, wind speed, and median volume diameter of the droplet. Combined with the simulation and natural icing experiments, it is observed that ice branches grow in the direction of electric field force, and as the voltage rises, ice branches gradually spread from the edge of the shed to its surface, increasing surface roughness. The density of ice exhibits an inverted U-shaped relationship as the electric field strength increases. Ice mass and ice length present nonlinear growth with an increase in icing time. Furthermore, compared with that without energization, the icing amount and icing length increase by more than 13 % under AC voltage of 40 kV.