Key Technology Research On Cable Accessories Of ±320kV DC Transmission

High Voltage Direct Current(HVDC)transmission plays an important role in facilities,such as high-capacity long-distance transmission,power system interconnection,DC transmission and distribution networks of metropolitan underground cable and long-distance submarine cables.With the development for HVDC power transmission system,the demand of high voltage DC cable accessories is increasing in domestic markets.However,the attachment is the weak link in the cable transmission system.It is the guarantee of improving the reliability and safety of cable accessories for cable systems.In this paper,±320kV DC cable accessories(integral prefabricated cable intermediate joint,composite prefabricated cable intermediate joint,prefabricated porcelain cable termination)for the design of objects were researched.It encompassed several key questions including material selection,simulation calculation of cable accessories and design of the stress cone.First,The mechanical and electric property of two kinds of insulation materials of SIR and EPDM were analyzed in detail.The basic parameters and conductivity function of materials was determined by the experiment.Proposing the main cable insulation material selection basis for the insulation of the electric field on the interface strength was relatively uniform,the electric field intensity around the cone roots could be effectively reduced and the density of space charge was the smallest when the ratio of SIR and XLPE was 10 based on the optimization analysis of conductance parameters adaptability with COMSOL.The second task was the selection of illustrating which type of joints is more suitable for high voltage DC cable.The analysis of the advantages and disadvantages of integral prefabricated and composite prefabricated intermediate joint was also necessary.Third was research into the variation of local field strength caused by size modification.Nevertheless,the effect of altering dimensions is not as strong as material modification,but more targeted.In consequence,the design of HVDC cable intermediate joint should be given priority over the development of the material and should be supplemented by correction of size.Final comes the design of the structure and size of Mould Melt Joint(MMJ)in ensuring the long-term safety and stable operation of HVDC cable accessories.Combining simulation design with optimized analysis was investigated in this work,successfully completing the design of ±320kV DC flexible cable accessories.Research results provided technical support for the Xiamen two-terminal VCS-HVDC demonstration project,offering a reference for VCS-HVDC project in the future.