Estimation of Breakdown Strength of Solid Insulating Materials in Ambient Medium

The objective of this research was to determine if a relationship could be found between dielectric strength and other properties of electrical insulating materials in ambient medium on an empirical basis by using variables predicted by basic theory. A simple equation of the form E=A+Blog (ρ _v/ξ _r tanδ) to predict the dielectric strength of a solid insulating material in the ambient medium has been proposed using ASTM electrode system. The constant ‘B’ has been obtained as a function of thickness ‘t’ of solid insulating materials. The equation requires the values of volume resistivity (v), relative permittivity (ξ _r) and loss tangent (tanδ), which may be obtained easily by low voltage non-destructive measurements. The values of electric strength calculated using this equation for Polyethylene, Fibre-glass, Leatheroid, Mica, Empire cloth, Kraft paper and Polyethylene coated Leatheroid are quite in agreement with the experimentally measured values. It is expected that the equations obtained will help the designers as a handy tool for quick estimation of breakdown strength of solid dielectrics.