Field Distribution in HVDC Cable Accessories: Shaping Field Control Elements

Thermal and electrical modelling are key actions in the design of HVDC cable accessories as the experimental means for probing field distribution in such objects are still in their infancy. In this work, based on a conductivity law established from experiments on typical materials that are XLPE (crosslinked polyethylene) and EPDM (ethylene-propylene diene monomer) copolymer, we compute the field distribution in a model of 200 kV cable joint using Comsol FEM software. Alternatives in the design of stress distribution are tested for different kinds of joint materials and different thermal conditions. Although relaxation of the tangential field at hot points along the interface between cable insulation and joint insulation can be obtained, not all the process for the establishment of field distribution is mastered due to the complexity in both the object geometry and in the temperature and field dependence of the materials electrical conductivity. The paper points to the need of optimization tools to identify best conditions.