Simulation Study on Temperature Distribution and Ampacity of HVDC Submarine Cable Laid in Cable Trench

Steady-state ampacity and temperature are key parameters reflecting the operating status of high-voltage direct current (HVDC) submarine cables. A two-dimensional (2D) simulation model of the ±160 kV submarine cable in a trench-laying method has been established using COMSOL Multiphysics finite element software. The influence factors of temperature distribution, electric field distribution and ampacity of submarine cable are studied when the fluid medium of cable trench is air and water respectively. The results show that there are differences in the temperature difference across different radial inner and outer surfaces of the submarine cable insulation layer, with the greatest temperature difference occurring along the direction of gravity. The critical temperature difference for the reversal of the electric field distribution in the insulating layer, with the center acting as the pivot, is 7.4°C, and the field strength at the center remains constant at 10.0kV/mm. The steady-state ampacity, limited by the conductor temperature and the insulation layer temperature difference, shows a crossing point on the curve as the ambient temperature changes. Filling the cable trench with water significantly improve the ampacity. Increasing the width of the cable trench and reducing the thickness of the cover plate can improve the submarine cable's ampacity to a certain extent, with more pronounced effects when the fluid medium is water.