On Ultimate Limit State Assessment for Dynamic Power Cables on Floating Wind Turbines

Abstract Ultimate Limit State (ULS) analysis of dynamic power cables in floating wind applications, such as inter-array cables (IACs), involves load cases derived from Floating Wind Turbine (FWT) components, including mooring systems, blades, and towers, as defined by industry standards. Due to the proprietary nature of turbine components, such as blades and controllers, cable manufacturers often rely on simplified models using first-order motion displacement Response Amplitude Operators (RAOs) obtained from detailed FWT analyses, typically conducted with fully coupled aero-hydrodynamic-structural models. This study presents ULS analysis for FWT IACs comparing fully coupled and simplified models. Two ULS Design Load Cases (DLCs) are evaluated using three approaches: (a) a fully coupled model, (b) a simplified first-order displacement RAO model with maximum design offset, and (c) a simplified RAO model with offsets derived from coupled analysis. Key metrics, such as minimum bend radius (MBR), tension and seabed clearance are compared. Results show that approach (b) is overly conservative, while approach (c) matches fully coupled outcomes, offering computational efficiency for early-stage design and load-case screening. A “drag disk” model, representing an intermediate level of complexity, is also briefly assessed, with detailed future study proposed. This framework is also proposed as future work for fatigue analysis, comparing fully coupled models with simplified approaches.