Electrical stress and inception voltage of discharges in gaseous cavities in an anisotropic dielectric material

The electric field stress and the inception voltage of discharges in a gaseous void present in an anisotropic dielectric material is developed from the solution of the Laplace equation. The relevant equations for the determination of the electric field and the inception voltage of discharges in voids are presented in a format that can be readily used. The electric field distribution within the void and the maximum field value are determined for two shapes of voids, rectangular and cylindrical cross sections, over wide ranges of anisotropy and sizes of voids. It has been found that the maximum electric field in the void increases with increasing width and decreases with increasing thickness of the void. The inception voltage of discharges is determined over a wide range of void dimensions. The minimum breakdown voltage of a slab of anisotropic dielectric material containing a void follows a U-shaped curve when plotted against the product of the length and width of the void.