Effect of Sheath Plastic Deformation on Electric Field in Three Core Submarine Cables

The integration of offshore wind farms has caused an increase in the number of submarine three core cables used. In these heavily and dynamically loaded circuits, cables face thermomechanical stresses that could affect the cable electrical performance. Existing electrical test standards test only single cores, which are highly concentric, not fully laid up cables, which may be more eccentric. It is known that Aluminium and lead are ductile materials and during high cable loading, the sheath could yield, increasing the possibility of creating gaps or voids at the interface. If the electric field within any void surpasses a critical field, a discharge will be ignited. Using FEM, a 2-D thermal-mechanical coupled analysis of a three core cable was established in order to investigate the mechanical stresses generated in cable that would affect the shape of the insulation, and hence the electric field. The deformed cable model is then studied through an electrical model, to understand how the elastic plastic deformation of the sheath will affect the performance of the cable electrically. It was found that high intensity electric field is established in the deformed regions.