IEC 61400-3-2 Ed. 1.0 b:2025

IEC 61400-3-2:2025 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.

This first edition cancels and replaces IEC TS 61400-3-2, published in 2019. This edition includes the following significant technical changes with respect to IEC TS 61400 3-2:

• a) The relevant contents of IEC 61400-3-1 have been migrated into IEC 61400-3-2, making IEC 61400-3-2 a self-standing document that does not have to be read directly in conjunction with IEC 61400-3-1.
• b) Several modifications have been made regarding metocean conditions in Clause 6 considering the nature of FOWT and the offshore site where FOWT will be installed, including:
  • (1) the importance of wave directional spreading has been highlighted as it may result in larger loads for FOWT, including the addition of the new informative Annex O and Annex P
  • (2) the characteristic of swell has been explained, which may be relevant for some FOWT projects, including the addition of new informative Annex R regarding the characteristic of swell.
• c) Subclauses 7.1, 7.2, 7.3, 7.4 and 7.5 have been changed to include a revised DLC table and its related descriptions, including amongst others updated requirements on directionality, wave conditions, redundancy check and damage stability cases, and a robustness check case; further updates are made related to guidance and necessities provided on load calculations and simulation requirements.
• d) Subclause 7.6 has been updated with guidance on fatigue assessment along with clarifications on serviceability analysis and the applicable material for WSD; related Annex L has been updated and a new Annex M has been added for clarification of the safety factors and load and load effect approach for floating substructures.
• e) The concept of floater control system that will interact with the wind turbine controller has been introduced in Clause 8.
• f) Clause 11 has been renamed from "Foundation and substructure design" to "Anchor design" and requirements for the transient conditions have been added.
• g) A more detailed clause regarding concrete design has been added to Clause 16 together with an informative Annex Q.
• h) Clause 15 has been updated with the aim to improve ease of use, using experience from oil and gas and considering unique wind turbine characteristics; updates included guidance for TLPs, damage stability, dynamic stability, testing and the addition for Annex S regarding how to analyse collision probability.