Corona Discharge from Water Droplet on Electrically Stressed Polymer Surface

This paper describes the results of experiments and simulations made to examine the corona discharges from water droplets on a polymer surface exposed to electrical stress. In this study, water droplets with different conductivities and volumes were placed on the surface of plate-shaped high temperature vulcanized silicone rubber (HTV-SR) energized with ac voltage, and the corona discharge phenomena were observed by a high-speed camera with an image intensifier. The electric-field distributions were calculated by the finite element method (FEM). It is demonstrated that the electric field is intensified at the triple junction of the water droplet, air and the insulating material due to the difference in their permittivities, which can ionize the surrounding air and trigger a corona discharge. It can also be confirmed that the contact angle, volume, conductivity and number of water droplets are shown to have a marked effect on the mode of the corona discharge development.