Research on simplified equivalent method of 3D simulation model for temperature distribution of HVDC submarine cables

Temperature distribution and ampacity are the two important parameters to reflect the operating state of a cables. According to the ±160kV DC submarine XLPE cable of Nan'ao multi-terminal VSC system, the three-dimensional (3D) transient simulation model of the temperature distribution of the submarine cable under the typical ampacity was set up by using the COMSOL Multiphysics finite element analysis software, and a simplified equivalent method of the model was proposed. Multiple thin layers and the adjacent medium were used as three equivalent layers. The thermal conductivity of the equivalent layer was handled by harmonic mean method, and the specific heat capacity and density of the equivalent layer were calculated according to IEC 60287 standard, which solved the problem that the mesh generation in thin layer of the submarine cable was too dense in simulation. By comparing the model to the steady state and transient temperature distribution of the cable and the calculation time before and after simplification and equivalence under the typical ampacity, the correctness of the simplified equivalent method is verified and greatly reduces the calculation time.