Analysis of the Ampacity Characteristics of Submarine Cables Considering the Permeability of Seabed Soil

Submarine cable ampacity is governed by the heat dissipation characteristics of the surrounding seabed. Conventional ampacity calculation methods, such as IEC 60287, evaluate external heat transfer mainly using soil thermal resistivity and ambient temperature, whereas the influence of natural convection in saturated seabed soils has received relatively little attention. Because permeability controls pore-water flow in porous media, it is expected to affect both heat transfer and cable ampacity. In this study, the influence of seabed soil permeability on the ampacity of submarine cables was investigated using a finite element thermo-fluid coupled model based on the Brinkman momentum equation and the energy equation. An AC 154 kV XLPE 3-Core 500 mm² submarine cable buried in saturated seabed soil was analyzed under various permeability conditions, and the numerical results were compared with those obtained using IEC 60287. The analysis showed that ampacity remained nearly unchanged in the low-permeability region, whereas it increased markedly once permeability reached the convection-dominant range, with a maximum value of 864 A. In addition, the dominant environmental factor affecting ampacity changed with permeability. Soil thermal resistivity had a greater influence under low-permeability conditions, while ambient temperature became more influential as natural convection intensified in high-permeability soils. These results indicate that permeability alters the heat-transfer mechanism around submarine cables and should be considered together with soil thermal resistivity and ambient temperature when evaluating cable ampacity in saturated seabed environments.