Research on drift limits for floating offshore substations based on the mechanical strength of dynamic cables

Floating Offshore Substations (FOSSs) are essential for far-offshore wind power. However, their design is constrained by the inherent conflict between load-bearing capacity and draft limitations. This challenge has kept FOSSs primarily at the conceptual stage, with a lack of mature design guidelines and established displacement criteria that is established to protect critical submarine cables. This study focused on the dynamic characteristics of submarine cables connected to FOSSs, and simulated a Cable–FOSSs model under dynamic wave load control. The tensile tension and bending curvature of the 100-m-deep cable under different design loads were measured. The maximum displacement of the top FOSSs when the cable first reached tensile or bending failure was analyzed, and optimization schemes related to cable attachments were made based on the failure forms. The simulation results show that the failure location and form of the cable connected to FOSSs are closely related to the layout. The obtained displacement limit is approximately 9-13% of the water depth. After optimization, the maximum value can reach 17.5% of the water depth. This provides key design criteria for the overall design of FOSSs and promotes the further construction of large-scale wind power facilities in the deep sea. • The coupled tensile-bending behavior of floating substations and subsea composite cables under wave loads was revealed. • The relationship between dynamic cables' ultimate capacity and platform’s horizontal displacement was quantified. • The drift limit of FOSS at a 100 m water depth was precisely determined via multi-parameter numerical analysis. • An optimized scheme affecting platform horizontal limits was provided, considering cable alignment and buoy specifications.