Influences of water droplet size and pollution layer permittivity on the electric field and potential distribution on a polluted insulator surface

Abstract

Presence of water droplets on a polluted outdoor high voltage insulator surface modifies the electric field flux and the equipotential distribution along the insulator surface. The water droplet may appear in different forms and sizes. The form is defined, here, by the angle shape between the water droplet surface and that of the insulator, which is kept constant at 90 degrees. The droplet size is specified by the diameter. The water droplet may measure from less than 90 degrees (hydrophilic) up to greater than 90 degrees (hydrophobic), depending on the properties of insulator surface. The present work describes a detailed numerical computation of the electric field and the potential distribution in the surroundings of water droplet on a polluted insulator surface. The computations are carried out using the Femlab package 3.1, which is based on the finite element method. The parameters used in the numerical analysis are the size of the water droplet and the pollution layer permittivity which describes the possible wetting conditions of the layer (i.e. clean, semi-wetted, and fully-wetted polymer surface). Detailed plots of the potential and field distribution in the inter electrode space, with and without the presence of a water droplet, were generated. The results showed that the electric field close to the water droplet tends to be higher as the diameter of the droplet increases, and lower as the relative permittivity of the pollution layer increases.

Effect of Dew and Raindrops on Electric Field around EHV Transmission Lines

“…The research of electric field at which the insulator surface has been polluted showed that the electric field close to the water droplet tends to be higher as the diameter of the droplet increases, and becomes lower as the relative permittivity of t he pollution layer increases [2]. In practice, the presence of water droplets over the insulator surface creates locations of high [3].…”