Thermal aspects of submarine cables in bend stiffeners

Abstract

This paper examines thermal behavior of a submarine power cable placed in a bend stiffener. The severity of thermal conditions for power cables in offshore platform installations is emphasized. First, a finite element analysis (FEM) of such an installation fully submerged in water is performed to determine which aspects of the model have the greatest influence on the computed temperature of the cable. This is followed by the development of the analytical model for current rating calculations for submarine installations considering short thermal bottlenecks. The analytical model implements the Galerkin approach for solving steady-state axisymmetric heat conduction problem. The FEM study shows the importance of the applied boundary conditions for the convective heat transfer in the gap between the inner diameter of the bend stiffener and the diameter of the cable. For the power cable rating calculations purpose, if the heat from the cable surface in a semi-enclosed water gap is assumed to dissipate by conduction only, pessimistic results of the cable ampacity are obtained. On the other hand, for the installation of the submarine cable in the bend stiffener placed in air examined with FEM analyses, the results suggest that the convective component in the gap may be disregarded.