BS EN IEC 61400-3-2:2025

Wind energy generation systems. Design requirements for floating offshore wind turbines | Status: Current

1 Scope This part of IEC 61400 specifies requirements for assessment of the external conditions at a floating offshore wind turbine (FOWT) site and specifies essential design requirements to ensure the engineering integrity of FOWTs. Its purpose is to provide an appropriate level of protection against damage from all anticipated hazards during the planned lifetime. This document focuses on the engineering integrity of the structural components of a FOWT but is also concerned with subsystems such as control and protection mechanisms, internal electrical systems and mechanical systems. A wind turbine shall be considered as a FOWT if the floating substructure is subject to hydrodynamic loading and supported by buoyancy and a stationkeeping system. A FOWT encompasses five principal subsystems: the RNA, the tower, the floating substructure, the stationkeeping system and the onboard machinery, equipment and systems that are not part of the RNA. The following types of floating substructures are explicitly considered within the context of this document:

• • ship-shaped structures and barges,
• • semi-submersibles (Semi),
• • spar buoys (Spar),
• • tension-leg platforms/buoys (TLP / TLB).

This document can be utilized for structural types other than listed above, but special consideration may be needed to support novel features to achieve the same target safety level. These other structures can have a great range of variability in geometry, materials and structural forms and, therefore, can be only partly covered by the requirements of this document. In other cases, specific requirements stated in this document can be found not to apply to all or part of a structure under design. In all the above cases, conformity with this document will require that the design is based upon its underpinning principles and achieves a level of safety equivalent, or superior, to the level implicit in it. This document is applicable to unmanned floating structures with one single horizontal axis turbine. While generally applicable, additional considerations may be needed, e.g., for multi-turbine units on a single floating substructure, vertical-axis wind turbines, FOWTs with shared moorings, spinning spars, floating structures without a stationkeeping system, or combined wind/wave energy systems. This document is to be used together with the appropriate IEC and ISO standards mentioned in Clause 2. In particular, this document is fully consistent with the requirements of IEC 61400‑1. In the event of requirements that may conflict between this document and the normative references, the requirements stated in this document supersede those of the references.