Offshore Wind Turbine

IEC TS 61400-3-2:2019 specifies additional 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 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 is considered as a FOWT if the floating substructure is subject to hydrodynamic loading and supported by buoyancy and a station-keeping system. A FOWT encompasses five principal subsystems: the RNA, the tower, the floating substructure, the station-keeping system and the on-board 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: a) ship-shaped structures and barges, b) semi-submersibles (Semi), c) spar buoys (Spar), d) tension-leg platforms/buoys (TLP / TLB). In addition to the structural types listed above, this document generally covers other floating platforms intended to support wind turbines. These other structures can have a great range of variability in geometry 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. Additional considerations might be needed for multi-turbine units on a single floating substructure, vertical-axis wind turbines, 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 intended to be fully consistent with the requirements of IEC 61400-1 and IEC 61400-3-1. The safety level of the FOWT designed according to this document is to be at or exceed the level inherent in IEC 61400‑1 and IEC 61400-3-1.

IEC 61400-3-1:2019 outlines the minimum design requirements for fixed offshore wind turbines and is not intended for use as a complete design specification or instruction manual. Several different parties may be responsible for undertaking the various elements of the design, manufacture, assembly, installation, erection, commissioning, operation and maintenance of an offshore wind turbine and for ensuring that the requirements of this document are met. The division of responsibility between these parties is a contractual matter and is outside the scope of this document. This edition cancels and replaces the first edition of IEC 61400-3 published in 2009. This edition includes the following significant technical changes with respect to the first edition of IEC 61400-3: a) The design load table has been revised to simplify the approach to waves, both for several gust cases with the Normal Sea State, and for a number of cases with the Extreme Sea State. The guidance for load calculations has been altered accordingly; c) For load safety factors reference is now made directly to IEC 61400-1; d) Control system has been aligned with the latest updates in IEC 61400-1; e) Wave spectra has been replaced by a reference to ISO 19901-1; f) The annex on ice loading has been revised and updated; g) Two informative annexes concerning tropical cyclones have been introduced; h) Other parts of the text have been aligned with IEC 61400-1