Wind energy generation systems - Part 3-1: Design requirements for fixed offshore wind turbines

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e) Wave spectra has been replaced by a reference to ISO 19901-1;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

Systèmes de génération d’énergie éolienne - Partie 3-1: Exigences de conception des éoliennes en mer fixes

l'IEC 61400-3-1:2019 spécifie des exigences complémentaires d'évaluation des conditions externes sur un site d'éoliennes en mer, ainsi que les exigences essentielles de conception, afin d'assurer l'intégrité technique des éoliennes en mer fixes. Elle a pour objet de fournir un niveau de protection approprié contre les dommages causés par tous les dangers pendant la durée de vie prévue.
Le présent document se concentre sur l'intégrité technique des éléments de structure d'une éolienne en mer, mais concerne également les sous-systèmes, tels que les mécanismes de commande et de protection, les systèmes électriques internes et les systèmes mécaniques.
Cette édition annule et remplace la première édition de l'IEC 61400-3 parue en 2009. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à la première édition de l'IEC 61400-3:
a) Le tableau des charges de conception a été révisé afin de simplifier l'approche par vagues, à la fois pour plusieurs cas de rafales avec l'état de mer normale et pour de nombreux cas avec l'état de mer extrême. Les recommandations concernant les calculs de charge ont été modifiées en conséquence;
b) Pour les facteurs de sécurité de charge, il est désormais fait directement référence à l'IEC 61400-1;
c) Le système de commande a été aligné sur les dernières mises à jour de l'IEC 61400-1;
d) La première édition consacrée aux spectres d'ondes a été remplacée par une référence à l'ISO 19901-1;
e) L'annexe consacrée aux surcharges de glace a été révisée et mise à jour
f) Deux annexes informatives concernant les cyclones tropicaux ont été introduites:
g) Les autres parties du texte ont été alignées sur l'IEC 61400-1.

General Information

Status
Published
Publication Date
04-Apr-2019
Current Stage
PPUB - Publication issued
Completion Date
05-Apr-2019
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IEC 61400-3-1
Edition 1.0 2019-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 3-1: Design requirements for fixed offshore wind turbines
Systèmes de génération d'énergie éolienne –
Partie 3-1: Exigences de conception des éoliennes en mer fixes
IEC 61400-3-1:2019-04 (en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61400-3-1
Edition 1.0 2019-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 3-1: Design requirements for fixed offshore wind turbines
Systèmes de génération d'énergie éolienne –
Partie 3-1: Exigences de conception des éoliennes en mer fixes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-7609-9

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61400-3-1:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 7

INTRODUCTION ..................................................................................................................... 9

1 Scope ............................................................................................................................ 10

2 Normative references .................................................................................................... 10

3 Terms and definitions .................................................................................................... 11

4 Symbols and abbreviated terms ..................................................................................... 19

4.1 Symbols and units................................................................................................. 19

4.2 Abbreviations ........................................................................................................ 20

5 Principal elements ......................................................................................................... 21

5.1 General ................................................................................................................. 21

5.2 Design methods .................................................................................................... 21

5.3 Safety classes ...................................................................................................... 22

5.4 Quality assurance ................................................................................................. 22

5.5 Rotor–nacelle assembly markings ......................................................................... 23

6 External conditions – definition and assessment ............................................................ 23

6.1 General ................................................................................................................. 23

6.2 Wind turbine classes ............................................................................................. 24

6.3 Definition of external conditions at an offshore wind turbine site ........................... 24

6.3.1 General ......................................................................................................... 24

6.3.2 Wind conditions ............................................................................................. 25

6.3.3 Marine conditions .......................................................................................... 25

6.3.4 Electrical power network conditions ............................................................... 32

6.3.5 Other environmental conditions ..................................................................... 32

6.4 Assessment of external conditions at an offshore wind turbine site ....................... 33

6.4.1 General ......................................................................................................... 33

6.4.2 The metocean database ................................................................................ 33

6.4.3 Assessment of wind conditions ...................................................................... 34

6.4.4 Assessment of marine conditions ................................................................... 36

6.4.5 Assessment of other environmental conditions .............................................. 40

6.4.6 Assessment of electrical network conditions .................................................. 41

6.4.7 Assessment of soil conditions ........................................................................ 41

7 Structural design ........................................................................................................... 42

7.1 General ................................................................................................................. 42

7.2 Design methodology ............................................................................................. 42

7.3 Loads.................................................................................................................... 42

7.3.1 General ......................................................................................................... 42

7.3.2 Gravitational and inertial loads ...................................................................... 42

7.3.3 Aerodynamic loads ........................................................................................ 43

7.3.4 Actuation loads .............................................................................................. 43

7.3.5 Hydrodynamic loads ...................................................................................... 43

7.3.6 Sea/lake ice loads ......................................................................................... 43

7.3.7 Other loads .................................................................................................... 44

7.4 Design situations and load cases .......................................................................... 44

7.4.1 General ......................................................................................................... 44

7.4.2 Power production (DLC 1.1 to 1.6) ................................................................. 50

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IEC 61400-3-1:2019 © IEC 2019 − 3 −
7.4.3 Power production plus occurrence of fault or loss of electrical network

connection (DLC 2.1 – 2.5) ............................................................................ 51

7.4.4 Start up (DLC 3.1 to 3.3)................................................................................ 53

7.4.5 Normal shutdown (DLC 4.1 to 4.2) ................................................................. 54

7.4.6 Emergency stop (DLC 5.1) ............................................................................. 54

7.4.7 Parked (standstill or idling) (DLC 6.1 to 6.4) .................................................. 55

7.4.8 Parked plus fault conditions (DLC 7.1 to 7.2) ................................................. 56

7.4.9 Transport, assembly, maintenance and repair (DLC 8.1 to 8.4) ...................... 57

7.4.10 Sea/lake ice design load cases ...................................................................... 60

7.5 Load and load effect calculations .......................................................................... 61

7.5.1 General ......................................................................................................... 61

7.5.2 Relevance of hydrodynamic loads .................................................................. 61

7.5.3 Calculation of hydrodynamic loads ................................................................. 62

7.5.4 Calculation of sea/lake ice loads .................................................................... 62

7.5.5 Overall damping assessment for support structure response evaluations ....... 62

7.5.6 Simulation requirements ................................................................................ 64

7.5.7 Other requirements ........................................................................................ 65

7.6 Ultimate limit state analysis................................................................................... 66

7.6.1 Method .......................................................................................................... 66

7.6.2 Ultimate strength analysis .............................................................................. 68

7.6.3 Fatigue failure ............................................................................................... 68

7.6.4 Special partial safety factors .......................................................................... 69

7.6.5 Assessment of cyclic loading for foundation assessment ............................... 69

8 Control system .............................................................................................................. 69

9 Mechanical systems ...................................................................................................... 70

10 Electrical system ........................................................................................................... 70

11 Foundation and substructure design .............................................................................. 70

12 Assembly, installation and erection ................................................................................ 71

12.1 General ................................................................................................................. 71

12.2 Planning ............................................................................................................... 72

12.3 Installation conditions ........................................................................................... 72

12.4 Site access ........................................................................................................... 72

12.5 Environmental conditions ...................................................................................... 73

12.6 Documentation ...................................................................................................... 73

12.7 Receiving, handling and storage ........................................................................... 73

12.8 Support structure systems .................................................................................... 73

12.9 Assembly of offshore wind turbine ......................................................................... 73

12.10 Erection of offshore wind turbine ........................................................................... 74

12.11 Fasteners and attachments ................................................................................... 74

12.12 Cranes, hoists and lifting equipment ..................................................................... 74

13 Commissioning, operation and maintenance .................................................................. 74

13.1 General ................................................................................................................. 74

13.2 Design requirements for safe operation, inspection and maintenance ................... 75

13.3 Instructions concerning commissioning ................................................................. 76

13.3.1 General ......................................................................................................... 76

13.3.2 Energization .................................................................................................. 76

13.3.3 Commissioning tests ...................................................................................... 76

13.3.4 Records ......................................................................................................... 76

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– 4 – IEC 61400-3-1:2019 © IEC 2019

13.3.5 Post commissioning activities ........................................................................ 76

13.4 Operator’s instruction manual ............................................................................... 76

13.4.1 General ......................................................................................................... 76

13.4.2 Instructions for operations and maintenance record ....................................... 77

13.4.3 Instructions for unscheduled automatic shutdown .......................................... 77

13.4.4 Instructions for diminished reliability .............................................................. 77

13.4.5 Work procedures plan .................................................................................... 77

13.4.6 Emergency procedures plan .......................................................................... 78

13.5 Maintenance manual ............................................................................................. 78

Annex A (informative) Key design parameters for an offshore wind turbine .......................... 80

A.1 Offshore wind turbine identifiers ............................................................................ 80

A.1.1 General ......................................................................................................... 80

A.1.2 Rotor-nacelle assembly (machine) parameters .............................................. 80

A.1.3 Support structure parameters ........................................................................ 80

A.1.4 Wind conditions (based on a 10-min reference period and including

wind farm wake effects where relevant) ......................................................... 80

A.1.5 Marine conditions (based on a 3-hour reference period where relevant) ........ 81

A.1.6 Electrical network conditions at turbine .......................................................... 81

A.2 Other environmental conditions ............................................................................. 82

A.3 Limiting conditions for transport, erection and maintenance .................................. 82

Annex B (informative) Shallow water hydrodynamics and breaking waves ............................ 83

B.1 Selection of suitable wave theories ....................................................................... 83

B.2 Modelling of irregular wave trains.......................................................................... 84

B.3 Wave height distributions ...................................................................................... 84

B.3.1 General ......................................................................................................... 84

B.3.2 The Goda model for maximum wave height ................................................... 84

B.3.3 The Battjes and Groenendijk wave height distribution .................................... 87

B.3.4 The Forristall wave and crest height distributions .......................................... 90

B.4 Breaking waves .................................................................................................... 92

B.5 Reference documents ........................................................................................... 95

Annex C (informative) Guidance on calculation of hydrodynamic loads ................................ 96

C.1 General ................................................................................................................. 96

C.2 Morison’s equation ................................................................................................ 97

C.3 Diffraction ............................................................................................................. 98

C.4 Slap and slam loading ........................................................................................... 99

C.5 Vortex-induced vibrations.................................................................................... 102

C.5.1 General ....................................................................................................... 102

C.5.2 Critical velocities for cross-flow motion ........................................................ 103

C.5.3 Critical velocities for in-line motion .............................................................. 104

C.6 Appurtenances .................................................................................................... 105

C.6.1 General ....................................................................................................... 105

C.6.2 Alternative method for estimating hydrodynamic coefficients accounting

for appurtenances and marine growth .......................................................... 105

C.7 Calculation methods ........................................................................................... 112

C.7.1 General ....................................................................................................... 112

C.7.2 Explicit approach ......................................................................................... 113

C.7.3 Constrained wave approach......................................................................... 113

C.8 Reference documents ......................................................................................... 113

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IEC 61400-3-1:2019 © IEC 2019 − 5 −

Annex D (informative) Recommendations for design of offshore wind turbine support

structures with respect to ice loads ..................................................................................... 115

D.1 Introductory remarks ........................................................................................... 115

D.2 General ............................................................................................................... 115

D.3 Choice of ice thickness ....................................................................................... 116

D.4 Load cases ......................................................................................................... 117

D.4.1 General ....................................................................................................... 117

D.4.2 Horizontal load from fast ice cover originating from temperature

fluctuations (DLC D1) .................................................................................. 117

D.4.3 Horizontal load from fast ice cover originating from water level

fluctuations and arch effect (DLC D2) .......................................................... 118

D.4.4 Horizontal load from moving ice (DLC D3, D4, D7 and D8) .......................... 118

D.4.5 Vertical load from fast ice cover (DLC D5) ................................................... 122

D.4.6 Pressure from ice ridges (DLC D6) .............................................................. 123

D.4.7 Dynamic loading (DLC D3, D4, D7, and D8)................................................. 123

D.5 Requirements on stochastic simulation ............................................................... 126

D.6 Requirements on model testing ........................................................................... 126

D.7 Reference documents ......................................................................................... 127

D.8 Databases for ice conditions ............................................................................... 129

Annex E (informative) Offshore wind turbine foundation and substructure design ............... 130

Annex F (informative) Statistical extrapolation of operational metocean parameters

for ultimate strength analysis .............................................................................................. 131

F.1 General ............................................................................................................... 131

F.2 Use of IFORM to determine 50-yr significant wave height conditional on

mean wind speed ................................................................................................ 131

F.3 Examples of joint distributions of V and H and approximations to the

environmental contour ........................................................................................ 133

F.4 Choice of sea state duration ............................................................................... 135

F.5 Determination of the extreme individual wave height to be embedded in SSS ..... 135

F.6 Reference documents ......................................................................................... 136

Annex G (informative) Corrosion protection ....................................................................... 137

G.1 General ............................................................................................................... 137

G.2 The marine environment ..................................................................................... 137

G.3 Corrosion protection considerations .................................................................... 138

G.4 Corrosion protection systems – Support structures ............................................. 138

G.5 Corrosion protection in the rotor–nacelle assembly ............................................. 139

G.6 Reference documents ......................................................................................... 140

Annex H (informative) Prediction of extreme wave heights during tropical cyclones ........... 141

H.1 General ............................................................................................................... 141

H.2 Wind field estimation for tropical cyclones ........................................................... 141

H.3 Wave estimation for tropical cyclones ................................................................. 142

H.4 Reference documents ......................................................................................... 142

H.5 Databases for tropical storms conditions ............................................................. 143

Annex I (informative) Recommendations for alignment of safety levels in tropical

cyclone regions ................................................................................................................... 144

I.1 General ............................................................................................................... 144

I.2 Global robustness level criteria ........................................................................... 144

I.3 Design load cases............................................................................................... 145

Bibliography ........................................................................................................................ 147

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– 6 – IEC 61400-3-1:2019 © IEC 2019

Figure 1 – Parts of a fixed offshore wind turbine ................................................................... 13

Figure 2 – Design process for an offshore wind turbine ......................................................... 22

Figure 3 – Definition of water levels ...................................................................................... 30

Figure 4 – The two approaches to calculate the design load effect ........................................ 67

Figure B.1 – Regular wave theory selection diagram ............................................................. 83

Figure B.2 – Comparison of wave height distribution results ................................................. 92

Figure C.1 – Breaking wave and cylinder parameters .......................................................... 100

Figure C.2 – Oblique inflow parameters .............................................................................. 101

Figure C.3 – Distribution over height of the maximum impact line force (γ = 0°) .................. 102

Figure C.4 – Response of model and full-scale cylinder in-line and cross-flow .................... 104

Figure C.5 – Geometrical definition of blocking and shielding ............................................. 109

Figure C.6 – Influence of a fixed boundary on the drag coefficient on a circular cylinder

5 6

in oscillatory supercritical flow KC > 20, R = 10 – 2 x 10 ................................................ 110

Figure C.7 – S
...

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