Electrical conduction in HVDC mass-impregnated paper cable

Abstract

HVDC cables play an important role in a growing number of HVDC links. For almost all of these cables, mass impregnated paper is used as electrical insulation. The electrical conductivity of this insulation is given by a commonly used empirical formula. This formula takes into account the temperature and stress dependency of the conductivity. This paper derives a physics-based equation describing ionic conduction. In good approximation this theoretical formula gives the same results as the empirical one. This makes it most likely that the conduction in paper mass impregnated cables is of the ionic kind. The derived formula uses some physical parameters like the inter-potential well distance, the potential well depth and the carrier concentration. Numerical values of these quantities for mass impregnated paper are given. According to the proposed model, the stress dependency results from the inter-potential well distance only. The temperature dependency results merely from the depth of the potential energy wells. In addition some possible underlying physical processes are described. >