Study on the Deformation of Water Droplets under a Time-Varying Electric Field [articol]

Abstract

Electric field enhancement due to the presence of water droplets on the insulation surface is one of the main factors reducing the flashover voltage of insulating material. To increase the electrical performance of an insulation system, the mechanisms of electric field intensification are important to study. This article presents the behavior of water droplets under a time-varying electric field. Water droplets under different voltage levels, from 0 to 3 kV, and various electrical stress directions, vertical and radial direction, were investigated. The deformation of water droplets was described by a system of equations, including Navier-Stokes equation and Poisson equation. In order to determine the interface between water and air, the level set method is chosen and applied to the models. According to the calculated results, the direction of the electric field has a significant effect on the deformation of the water droplet. Additionally, this research reveals that with higher input voltage, the degree of distortion is further increased from the equilibrium state; the shape of water droplet at zero-field. The field intensification of a deformed droplet is comparable between two different directions of electrical stress; vertical field and radial field respectively. However, these values are lower when compared with the results from a non-deformed droplet.