Survival and Durability Design of Dynamic Submarine Cable Under Extreme Operating Conditions

Extreme ocean waves and currents are the main causes of the violent movement and large-scale excursion of floating platforms, and they also directly impact dynamic submarine cables and mooring system. Dynamic cables are suspended from the platform to the seabed and present 'Lazy wave' configuration in the water-column to accommodate the platform’s motion. Their survivability under extreme sea conditions and durability under long-term marine environmental loads are the primary design objectives. Based on the typical marine environmental conditions of the floating wind turbine operation location in Nan Ri Island, Fujian Province, the Weibull statistical method was employed to model extreme wave and current conditions for 50-year and 100-year return periods. In accordance with design standards, hydrodynamic analysis and finite element software were utilized to conduct global loads analysis and local stress calculations for the submarine cable of a floating wind turbine successfully commissioned in China, thereby verifying its ultimate load-bearing capacity. The annual distribution and duration of wave parameters were statistically analyzed, and time-domain calculation methods combined with linear cumulative theory were used to verify the fatigue life of the submarine cable. Based on the fatigue life analysis results, a full-scale fatigue life test matrix for dynamic submarine cables was established, providing a reference and guidance for the survival and durability design of submarine cable under extreme conditions.