IEC TS 61400-3-2:2019

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

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.

General Information

• Status: Published
• Publication Date: 04-Apr-2019
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 27.180 - Wind turbine energy systems
• ICS: 31.240 - Mechanical structures for electronic equipment
• Technical Committee: TC 88 - Wind energy generation systems
• Drafting Committee: MT 3-2 - TC 88/MT 3-2
• Current Stage: PPUB - Publication issued
• Start Date: 14-Aug-2018
• Completion Date: 05-Apr-2019

Standards Content (Sample)

IEC TS 61400-3-2 ®
Edition 1.0 2019-04
TECHNICAL
SPECIFICATION
colour
inside
Wind energy generation systems –
Part 3-2: Design requirements for floating offshore wind turbines
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IEC TS 61400-3-2 ®
Edition 1.0 2019-04
TECHNICAL
SPECIFICATION
colour
inside
Wind energy generation systems –

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

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180 ISBN 978-2-8322-5986-3

– 2 – IEC TS 61400-3-2:2019 © IEC 2019
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Symbols and abbreviated terms . 12
4.1 Symbols and units. 12
4.2 Abbreviations . 12
5 Principal elements . 12
5.2 Design methods . 12
5.6 Support structure markings . 14
6 External conditions – definition and assessment . 14
6.1 General . 14
6.1.2 Wind conditions . 14
6.3.3 Marine conditions . 14
6.3.5 Other environmental conditions . 15
7 Structural design . 15
7.1 General . 15
7.3 Loads. 15
7.3.2 Gravitational and inertial loads . 15
7.3.3 Aerodynamic loads . 15
7.3.5 Hydrodynamic loads . 15
7.3.6 Sea/lake ice loads . 15
7.3.7 Other loads . 16
7.4 Design situations and load cases . 16
7.5 Load and load effect calculations . 18
7.5.1 General . 18
7.5.2 Relevance of hydrodynamic loads . 18
7.5.3 Calculation of hydrodynamic loads . 18
7.5.4 Calculation of sea/lake ice loads . 19
7.5.6 Simulation requirements . 19
7.5.7 Other requirements . 21
7.6 Ultimate limit state analysis. 21
7.6.1 General . 21
7.6.3 Fatigue failure . 22
7.6.6 Working stress design method . 22
7.6.7 Serviceability analysis . 23
8 Control system . 23
9 Mechanical systems . 24
10 Electrical systems . 24
11 Foundation and substructure design . 24
12 Assembly, installation and erection . 24
12.1 General . 24
12.2 General . 24
12.3 Planning . 25

12.13 Floating specific items . 25
13 Commissioning, operation and maintenance . 25
13.1 General . 25
13.3 Instructions concerning commissioning . 25
13.4 Operator’s instruction manual . 25
13.4.1 General . 25
13.4.6 Emergency procedures plan . 25
13.5 Maintenance manual . 25
14 Stationkeeping systems . 25
15 Floating stability . 26
15.1 General . 26
15.2 Intact static stability criteria . 26
15.3 Alternative intact stability criteria based on dynamic-response . 26
15.4 Damage stability criteria . 26
16 Materials . 27
17 Marine support systems . 27
17.1 General . 27
17.2 Bilge system . 27
17.3 Ballast system . 27
Annex A (informative) Key design parameters for a floating offshore wind turbine . 28
A.1 Floating offshore wind turbine identifiers . 28
A.1.1 General . 28
A.1.2 Rotor nacelle assembly (machine) parameters . 28
A.1.3 Support structure parameters . 28
A.1.4 Wind conditions (based on a 10-min reference period and including
wind farm wake effects where relevant) . 29
A.1.5 Marine conditions (based on a 3-hour reference period where relevant) . 29
A.1.6 Electrical network conditions at turbine . 30
A.2 Other environmental conditions . 30
A.3 Limiting conditions for transport, installation and maintenance . 31
Annex B (informative) Shallow water hydrodynamics and breaking waves . 32
Annex C (informative) Guidance on calculation of hydrodynamic loads . 33
Annex D (informative) Recommendations for design of floating offshore wind turbine
support structures with respect to ice loads . 34
Annex E (informative) Floating offshore wind turbine foundation and substructure
design . 35
Annex F (informative) Statistical extrapolation of operational metocean parameters
for ultimate strength analysis . 36
Annex G (informative) Corrosion protection . 37
Annex H (informative) Prediction of extreme wave heights during tropical cyclones . 38
Annex I (informative) Recommendations for alignment of safety levels in tropical
cyclone regions . 39
Annex J (informative) Earthquakes . 40
Annex K (informative) Model tests . 41
Annex L (informative) Tsunamis . 43
L.1 General . 43
L.2 Numerical model of tsunami [3],[4] . 43

– 4 – IEC TS 61400-3-2:2019 © IEC 2019
L.3 Evaluation of variance of water surface elevation and current velocity [5]
...