EN IEC 61400-3-2:2025

Wind energy generation systems - Part 3-2: Design requirements for floating offshore wind turbines

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 and (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.

Windenergieanlagen - Teil 3-2: Auslegungsanforderungen für schwimmende Windenergieanlagen auf offener See

Systèmes de génération d’énergie éolienne - Partie 3-2: Exigences de conception des éoliennes en mer flottantes

l'IEC 61400-3-2:2025 spécifie des exigences d'évaluation des conditions externes sur un site d'éoliennes en mer flottantes (FOWT), ainsi que les exigences essentielles de conception, afin d'assurer l'intégrité technique des FOWT. Elle a pour objet de fournir un niveau de protection approprié contre les dommages provoqués par tous les dangers prévus pendant la durée de vie prévue. Le présent document se concentre sur l'intégrité technique des composants structurels d'une FOWT, mais concerne également les sous-systèmes, tels que les mécanismes de commande et de protection, les systèmes électriques internes et les systèmes mécaniques. Cette première édition annule et remplace l'IEC TS 61400-3-2 parue en 2019. Cette première édition annule et remplace l'IEC TS 61400-3-2 parue en 2019. a) le contenu pertinent de l'IEC 61400-3-1 a été transféré dans l'IEC 61400-3-2, faisant de l'IEC 61400-3-2 un document autonome qui ne doit pas être lu directement conjointement avec l'IEC 61400-3-1; b) plusieurs modifications ont été apportées concernant les conditions océano-météorologiques spécifiées à l'Article 6 en prenant en compte la nature de la FOWT et le site en mer sur lequel la FOWT est installée, notamment: (1) l'importance de la propagation directionnelle des vagues a été soulignée, car elle peut entraîner des charges plus importantes pour la FOWT, y compris l'ajout des nouvelles Annexe O et Annexe P informatives, et (2) la caractéristique de la houle a été expliquée, ce qui peut être pertinent pour certains projets FOWT, y compris l'ajout d'une nouvelle Annexe R informative concernant la caractéristique de la houle; c) les 7.1, 7.2, 7.3, 7.4 et 7.5 ont été modifiés pour inclure un tableau de DLC (Design Load Case, cas de charge pour la conception) révisé et ses descriptions associées, y compris, entre autres, des exigences mises à jour sur la directionnalité, les conditions de vagues, les cas de contrôle de redondance et de stabilité après avarie, et un cas de contrôle de solidité; d'autres mises à jour sont effectuées concernant les recommandations et les éléments nécessaires fournis sur les calculs de charge et les exigences de simulation; d) le 7.6 a été mis à jour avec des recommandations relatives à l'évaluation de la fatigue ainsi que des clarifications sur l'analyse de l'aptitude au service et le matériel applicable pour le WSD. L'Annexe L connexe a été mise à jour et une nouvelle Annexe M a été ajoutée pour la clarification des facteurs de sécurité et l'approche de charge et d'effet de charge pour les sous-structures flottantes; e) le concept de système de commande de flotteur qui interagit avec le régulateur de l'éolienne a été introduit à l'Article 8; f) l'Article 11 "Conception de la fondation et de la sous-structure" a été renommé en "Conception des ancres" et des exigences relatives aux conditions transitoires ont été ajoutées; g) un article plus détaillé sur la conception du béton a été ajouté à l'Article 16 ainsi qu'une Annexe Q informative; h) l'Article 15 a été mis à jour dans le but d'améliorer la facilité d'utilisation, en utilisant l'expérience du pétrole et du gaz et en prenant en compte les caractéristiques uniques des éoliennes. Les mises à jour comprenaient des recommandations pour les TLP, la stabilité après avarie, la stabilité dynamique, les essais et l'ajout de l'Annexe S concernant la manière d'analyser la probabilité de collision.

Sistemi za proizvodnjo energije na veter - 3-2. del: Zahteve za načrtovanje plavajočih vetrnih turbin na morju (IEC 61400-3-2:2025)

General Information

• Status: Published
• Publication Date: 27-Feb-2025
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: CLC/TC 88 - Wind turbines
• Drafting Committee: IEC/TC 88 - IEC_TC_88
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 28-Feb-2025
• Due Date: 30-Dec-2022
• Completion Date: 28-Feb-2025
• Ref Project: SIST EN IEC 61400-3-2:2025 - Wind energy generation systems - Part 3-2: Design requirements for floating offshore wind turbines (IEC 61400-3-2:2025)

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2025
Sistemi za proizvodnjo energije na veter - 3-2. del: Zahteve za načrtovanje
plavajočih vetrnih turbin na morju (IEC 61400-3-2:2025)
Wind energy generation systems - Part 3-2: Design requirements for floating offshore
wind turbines (IEC 61400-3-2:2025)
Windenergieanlagen - Teil 3-2: Auslegungsanforderungen für schwimmende
Windenergieanlagen auf offener See (IEC 61400-3-2:2025)
Systèmes de génération d’énergie éolienne - Partie 3-2: Exigences de conception des
éoliennes en mer flottantes (IEC 61400-3-2:2025)
Ta slovenski standard je istoveten z: EN IEC 61400-3-2:2025
ICS:
27.180 Vetrne elektrarne Wind turbine energy systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61400-3-2

NORME EUROPÉENNE
February 2025
EUROPÄISCHE NORM
ICS 27.180
English Version
Wind energy generation systems - Part 3-2: Design
requirements for floating offshore wind turbines
(IEC 61400-3-2:2025)
Systèmes de génération d'énergie éolienne - Partie 3-2: Windenergieanlagen - Teil 3-2: Auslegungsanforderungen
Exigences de conception des éoliennes en mer flottantes für schwimmende Windenergieanlagen auf offener See
(IEC 61400-3-2:2025) (IEC 61400-3-2:2025)
This European Standard was approved by CENELEC on 2025-02-26. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 20252025 All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
CENELEC
Ref. No. EN IEC 61400-3-2:2025 E

European foreword
The text of document 88/1028/FDIS, future edition 1 of IEC 61400-3-2, prepared by TC 88 "Wind
energy generation systems" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 61400-3-2:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-02-28
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-02-29
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
This document is read in conjunction with EN IEC 61400-1.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61400-3-2:2025 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 61400-24 NOTE Approved as EN IEC 61400-24
ISO 12944-2 NOTE Approved as EN ISO 12944-2
ISO 12944-9 NOTE Approved as EN ISO 12944-9
ISO 13628-5 NOTE Approved as EN ISO 13628-5
ISO 19901-2 NOTE Approved as EN ISO 19901-2
ISO 19901-8 NOTE Approved as EN ISO 19901-8
ISO 19901-10 NOTE Approved as EN ISO 19901-10
IEC 60721-3-3 NOTE Approved as EN IEC 60721-3-3
ISO 12944-2 NOTE Approved as EN ISO 12944-2
ISO 12944-9 NOTE Approved as EN ISO 12944-9
ISO 19902 NOTE Approved as EN ISO 19902
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60721 series Classification of environmental EN 60721 series
IEC 61400-1 2019 Wind energy generation systems - Part 1: EN IEC 61400-1 2019
Design requirements
IEC 61400-3-1 - Wind energy generation systems - Part 3- EN IEC 61400-3-1 -
1: Design requirements for fixed offshore
wind turbines
IEC 61400-13 - Wind turbines - Part 13: Measurement of EN 61400-13 -
mechanical loads
IEC 61400-15-1 - Wind energy generation systems - Part 15- EN IEC 61400-15- -
1: Site suitability input conditions for wind 1
power plants
IEC 61400-24 - Wind energy generation systems - Part 24: EN IEC 61400-24 -
Lightning protection
ISO 2394 - General principles on reliability for - -
structures
ISO 2533 - Standard Atmosphere - -
ISO 18692-1 - Fibre ropes for offshore stationkeeping - - -
Part 1: General specification
ISO 18692-2 - Fibre ropes for offshore stationkeeping - - -
Part 2: Polyester
ISO 18692-3 - Fibre ropes for offshore stationkeeping - - -
Part 3: High modulus polyethylene (HMPE)
ISO 19900 - Petroleum and natural gas industries - EN ISO 19900 -
General requirements for offshore
structures
Under preparation. Stage at the time of publication: IEC/AFDIS 61400-15-1:2023.
Under preparation. Stage at the time of publication: FprEN IEC 61400-15-1:2024.
Publication Year Title EN/HD Year
ISO 19901-1 - Petroleum and natural gas industries - EN ISO 19901-1 -
Specific requirements for offshore
structures - Part 1: Metocean design and
operating considerations
ISO 19901-4 - Petroleum and natural gas industries - EN ISO 19901-4 -
Specific requirements for offshore
structures - Part 4: Geotechnical and
foundation design considerations
ISO 19901-6 - Petroleum and natural gas industries - EN ISO 19901-6 -
Specific requirements for offshore
structures - Part 6: Marine operations
ISO 19901-7 - Petroleum and natural gas industries - EN ISO 19901-7 -
Specific requirements for offshore
structures - Part 7: Stationkeeping systems
for floating offshore structures and mobile
offshore units
ISO 19902 - Petroleum and natural gas industries - EN ISO 19902 -
Fixed steel offshore structures
ISO 19903 - Petroleum and natural gas industries - EN ISO 19903 -
Concrete offshore structures
ISO 19904-1 - Petroleum and natural gas industries - EN ISO 19904-1 -
Floating offshore structures - Part 1: Ship-
shaped, semi-submersible, spar and
shallow-draught cylindrical structures
ISO 19906 - Petroleum and natural gas industries - EN ISO 19906 -
Arctic offshore structures
ISO 29400 - Ships and marine technology - Offshore - -
wind energy - Port and marine operations
IEC/TS 61400-30 2023 Wind energy generation systems - Part 30: - -
Safety of wind turbine generators - General
principles for design
API RP 2T - Planning, Designing, and Constructing - -
Tension Leg Platforms
IMO - International Code on Intact Stability - -
IMO - MODU CODE - -
IEC 61400-3-2 ®
Edition 1.0 2025-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Wind energy generation systems –

Part 3-2: Design requirements for floating offshore wind turbines

Systèmes de génération d’énergie éolienne –

Partie 3-2: Exigences de conception des éoliennes en mer flottantes

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180  ISBN 978-2-8322-9825-1

– 2 – IEC 61400-3-2:2025 © IEC 2025
CONTENTS
FOREWORD . 8
INTRODUCTION . 11
1 Scope . 12
2 Normative references . 13
3 Terms and definitions . 14
4 Symbols, units and abbreviated terms . 26
4.1 General . 26
4.2 Symbols and units. 26
4.3 Abbreviated terms . 27
5 Principal elements . 28
5.1 General . 28
5.2 Design methods . 28
5.3 Safety level for FOWT . 30
5.4 Safety classes for RNA and tower . 30
5.5 Quality assurance . 30
5.6 Rotor–nacelle assembly markings . 30
5.7 Support structure markings . 31
6 External conditions – definition and assessment . 31
6.1 General . 31
6.2 Wind turbine classes . 31
6.3 Definition of external conditions at a FOWT site . 32
6.3.1 General . 32
6.3.2 Wind conditions . 32
6.3.3 Marine conditions . 33
6.3.4 Electrical power network conditions . 40
6.3.5 Other environmental conditions . 40
6.4 Assessment of external conditions at a FOWT site . 41
6.4.1 General . 41
6.4.2 The metocean database . 41
6.4.3 Assessment of wind conditions . 42
6.4.4 Assessment of marine conditions . 44
6.4.5 Assessment of other environmental conditions . 48
6.4.6 Assessment of electrical network conditions . 49
6.4.7 Assessment of soil conditions . 49
7 Structural design . 50
7.1 General . 50
7.2 Design methodology . 51
7.3 Loads. 51
7.3.1 General . 51
7.3.2 Gravitational and inertial loads . 51
7.3.3 Aerodynamic loads . 51
7.3.4 Actuation loads .
...