Calculation of Space Charge and Field Distributions in a Cable Joint

At present, high-voltage direct current (HVDC) transmission technology is more and more widely used in long-distance transmission because of its low line cost, low loss and easy control. But under high-voltage DC electric field, the accumulation of space charge will occur in the DC insulation structure, leading to the distortion of electric field, and thus influencing the aging and failure of the insulation. Due to the limitation of space charge measurement methods, we can only obtain the space charge distribution of simple structures (e.g. films or coaxial cable samples), and the distribution of space charge in complex insulation structure cannot be directly measured. Therefore, it is necessary to simulate the distribution of space charge in complex insulation structure using simulation software based on the existing space charge transport theory. In this paper, based on COMSOL Multiphysics software, the space charge and field distribution in a 3-dimensional structure can be calculated. The model used in this paper is the bipolar charge transport model, to simulate the distribution of space charge and electric field in various insulation structures under the action of high voltage DC electric field. This paper calculates the space charge and electric field distribution in a cable joint under temperature gradient. Comparing with traditional way which only the conductivity was taken into consideration, this method can accurately reflect the electric field distortion caused by the difference of carrier injection, extraction and migration.