Temperature Field Simulation and Ampacity Optimization of 500kV HVDC Submarine Transmission Cable

The HVDC submarine power cables have complex structure and needs extraordinary manufacture process requirements. The HVDC submarine cable in an offshore wind farm usually goes through multiple laying sections with different laying environment. And in some of the sections, the heat dissipation condition may be unfavorable. To improve the safety of the transmission line, it is obligatory to study the cable temperature field and ampacity of power cable under different laying conditions and find the bottleneck sections, together with the methods to improve the ampacity of these weak sections. A 500kV XLPE submarine power cable is taken as the study object, the finite element modeling (FEM) is used to study the electromagnetic thermal coupling model of the submarine cables laying in the soil without trench, in the tube with water flowing for the purpose of forced cooling at beach section is established respectively to study the temperature field and ampacities by using COMSOL Multiphysics software. The results indicate that, water circulating in the tube would affect the cable heat dissipation and significantly ampacity is increased. Moreover, it has been noted that when the water flow rate is 2.78 L/s in the tube, the ampacity of cable is optimum and by the implementation of this proposed model the ampacity can be increased up to 650A.