Electric field determination in DC polymeric power cable in the presence of space charge and temperature gradient under dc conditions

In direct current (DC) power cable the electric field is affected by conductivity of the material, which is a function of both temperature and electric field. Loading in high voltage direct current (HVDC) cable results in a temperature gradient across the insulation and hence a radial distribution of the insulation conductivity. A direct consequence is the accumulation of space charge within the insulation bulk, which modifies the electric field across the insulation. The coupled problems due to electric field and temperature inflict difficulties to identify the electric field distribution in HVDC cables, which therefore poses threat to the reliability in operation of DC power cables. Space charge in a commercial 11 kV AC XLPE power cable has been measured under a voltage application of 80 kV dc. Space charge distributions were obtained across the insulation of the cable by means of a modified pulsed electroacoustic (PEA) system. In this paper, COMSOL Multiphysics software package is also used to accurately determine the electric field distribution in the dc power cable by considering the influences of both the effects of temperature and electric field on the conductivity of the insulating material.