Electric field simulation of air gap defects in HVDC cable accessories based on sub model method

HVDC cable accessories are one of the key equipment of DC transmission system. In order to study the influence of air gap defect on the electric field distribution of HVDC cable accessories, an electric field simulation method of HVDC cable accessories with air gap defect based on submodel method is proposed. Taking ± 200kV DC prefabricated intermediate joint as an example, a 3-D submodel of air gap defects is established, and the surface nodes of the submodel are mapped to the 2-D coordinate system. Taking the 2-D electric field simulation results of cable accessories at the same coordinate node as the known boundary condition of the submodel, the electric field distribution of the air gap defect is obtained, and the cutting boundary of the submodel is used for verification. The influence of the location and size of air gap defects on the electric field distortion is analyzed, and the theoretical critical size of partial discharge of air gap defects is obtained. The results show that when air gap defects in the insulating layer is located near the tip of semi conductive stress cone, the most serious electric field distortion occurs, and the half diameter of air gap should be controlled below 0.02mm. The research results are helpful to guide the production and manufacture of HVDC cable accessories.