Investigation of Electric Field Distribution in Power Cables with Voids

In a power cable, the main cause of dielectric breakdown is PDs in internal gaseous voids in the insulation. It is clearly desirable that the electric stress in such voids should be calculated in terms of the electric stress in the dielectric material. This paper presents the results of electric field distribution calculations in voids in power cable insulation. Various simple geometrical shapes of void are considered: spherical, elliptical and cylindrical. The analysis shows that the void field stress is stronger for a cylindrical shape than for a spherical void. Finite element analysis results indicate that the stress is influenced by the dielectric permittivity, the size of void, the number of voids along the field direction, the void orientation, the position of void and the thickness of insulation