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.