Steady-State Electric Field and Conductivity in Mass-Impregnated HVDC Cable Insulation

Abstract

This paper presents results from measurements and calculations of the steady-state DC electric field and the field-dependent conductivity in the two insulation materials found in mass-impregnated HVDC cables: Cable mass (a high-viscositymineral oil) and paper that is impregnated with that mass. An important assumption for the work was that the relationship between the electric fields in the two materials depends only on the relationship between their conductivities. It was found that the conductivity of the mass is 2–5 times higher than the conductivity of the impregnated paper during normal, steady-state conditions in cables. Consequently, the electric field in the impregnated paper is 2–5 times higher than the electric field in the mass under such conditions.