Analysis on the thermal performance and economic efficiency of XLPE submarine cable based on electric–thermal–hydraulic coupling simulation

The operating temperature of a submarine cable must be lower than its permissible limit to prevent degradation of the insulation material. Ground conditions influence the heat transfer between the cable and the surrounding soil, thereby affecting both the cable temperature and its economic efficiency. This paper investigates the effect of ground conditions on the thermal performance and economic efficiency of a three-core 220 kV AC XLPE submarine cable. A coupled finite element model based on electromagnetic, thermal, and pore water flow fields is developed and the effects of laying depth, initial temperature, soil thermal conductivity, and permeability on the thermal performance and economic efficiency of the cable are investigated via parametric studies. The results show that the conductor temperature increases with increasing laying depth, and this effect becomes more pronounced at greater laying depths. The conductor temperature increases linearly with increasing initial temperature and decreases nonlinearly with increasing soil thermal conductivity. When the soil permeability is greater than 10^-11 m², the conductor temperature decreases as the soil permeability increases. From a thermal-economic perspective, the economic efficiency of submarine cables can be improved by laying cables in soil with high thermal conductivity or decreasing the laying depth. Laying cables in soil with higher permeability to improve cost-effectiveness is effective only when the soil permeability exceeds 10⁻¹¹ m².