Wind energy generation systems - Part 5: Wind turbine blades

IEC 61400-5:2020 specifies requirements to ensure the engineering integrity of wind turbine blades as well as an appropriate level of operational safety throughout the design lifetime. It includes requirements for:
aerodynamic and structural design,
material selection, evaluation and testing,
manufacture (including associated quality management),
transportation, installation, operation and maintenance of the blades.  The purpose of this document is to provide a technical reference for designers, manufacturers, purchasers, operators, third party organizations and material suppliers, as well as to define requirements for certification.

Systèmes de génération d'énergie éolienne - Partie 5: Pales d’éoliennes

l’IEC 61400-5:2020 spécifie les exigences permettant d’assurer l’intégrité technique des pales d’éoliennes ainsi que le niveau approprié de sécurité fonctionnelle tout au long de la durée de vie prévue à la conception. Elle comprend des exigences concernant:
la conception aérodynamique et structurelle,
la sélection, l’évaluation et les essais des matériaux,
la fabrication (y compris le management associé de la qualité),
le transport, l’installation, le fonctionnement et la maintenance des pales.  Le présent document a pour objet de fournir une référence technique aux concepteurs, fabricants, acheteurs, opérateurs, organismes tiers et fournisseurs de matériaux, et de définir les exigences relatives à la certification.

General Information

Status
Published
Publication Date
15-Jun-2020
Current Stage
PPUB - Publication issued
Completion Date
16-Jun-2020
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IEC 61400-5
Edition 1.0 2020-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 5: Wind turbine blades
Systèmes de génération d’énergie éolienne –
Partie 5: Pales d’éoliennes
IEC 61400-5:2020-06(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61400-5
Edition 1.0 2020-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 5: Wind turbine blades
Systèmes de génération d’énergie éolienne –
Partie 5: Pales d’éoliennes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-8335-6

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61400-5:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 8

4 Notation ......................................................................................................................... 10

4.1 Symbols ................................................................................................................ 10

4.2 Greek symbols ...................................................................................................... 11

4.3 Subscripts ............................................................................................................. 11

4.4 Coordinate systems .............................................................................................. 11

5 Design environmental conditions ................................................................................... 12

6 Design ........................................................................................................................... 13

6.1 Structural design process...................................................................................... 13

6.1.1 General requirements .................................................................................... 13

6.1.2 Building block approach for composite structural design ................................ 13

6.1.3 General blade design process ....................................................................... 14

6.1.4 Design loads .................................................................................................. 17

6.2 Blade characteristics ............................................................................................. 18

6.2.1 Blade properties ............................................................................................ 18

6.2.2 Functional design tolerances ......................................................................... 18

6.3 Aerodynamic design .............................................................................................. 19

6.3.1 General ......................................................................................................... 19

6.3.2 Aerodynamic characteristics .......................................................................... 19

6.3.3 Power performance characterisation (informative) ......................................... 20

6.3.4 Airfoil noise (informative) ............................................................................... 20

6.4 Material requirements ........................................................................................... 20

6.4.1 General ......................................................................................................... 20

6.4.2 Material properties for blade design ............................................................... 20

6.4.3 Qualification of materials for manufacture ...................................................... 24

6.5 Design for manufacturing ...................................................................................... 25

6.5.1 General ......................................................................................................... 25

6.5.2 Requirement for manufacturing tolerances ..................................................... 25

6.6 Structural design ................................................................................................... 26

6.6.1 General design approach ............................................................................... 26

6.6.2 Structural analysis ......................................................................................... 27

6.6.3 Verification requirements ............................................................................... 29

6.6.4 Partial safety factors for materials ................................................................. 30

6.6.5 Structural design verification.......................................................................... 34

6.6.6 Additional failure modes ................................................................................ 47

7 Manufacturing requirements .......................................................................................... 48

7.1 Manufacturing process .......................................................................................... 48

7.2 Workshop requirements ........................................................................................ 48

7.2.1 General ......................................................................................................... 48

7.2.2 Workshop facilities ........................................................................................ 49

7.2.3 Material handling and storage facilities .......................................................... 49

7.2.4 Tools and equipment ..................................................................................... 50

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IEC 61400-5:2020 © IEC 2020 – 3 –

7.2.5 Personnel ...................................................................................................... 51

7.3 Quality management system requirements ............................................................ 52

7.4 Manufacturing process requirements..................................................................... 52

7.4.1 General manufacturing requirements ............................................................. 52

7.4.2 Gelcoat application to the mould .................................................................... 52

7.4.3 Building up the laminate ................................................................................ 53

7.4.4 Adhesive bonding process ............................................................................. 54

7.4.5 Curing ........................................................................................................... 55

7.4.6 Demoulding ................................................................................................... 55

7.4.7 Trimming, cutting, and grinding ...................................................................... 55

7.4.8 Surface finish ................................................................................................ 56

7.4.9 Sealing .......................................................................................................... 56

7.4.10 Additional component assembly processes .................................................... 56

7.4.11 Mass and balance .......................................................................................... 57

7.4.12 Manufacturing and assembly processes outside controlled environment ........ 57

7.5 Manufacture of natural fiber-reinforced rotor blades .............................................. 57

7.6 Other manufacturing processes ............................................................................ 58

7.7 Quality control process ......................................................................................... 58

7.7.1 Manufacturing quality plan ............................................................................. 58

7.7.2 Incoming inspection ....................................................................................... 58

7.7.3 Manufacturing and quality control records ...................................................... 58

7.7.4 Non-conformity process ................................................................................. 59

7.7.5 In manufacture corrective action processes ................................................... 59

7.7.6 Final manufacturing inspection and conformity review ................................... 60

7.7.7 Documentation .............................................................................................. 60

7.8 Requirements for manufacturing evaluation .......................................................... 61

8 Blade Installation, operation and maintenance ............................................................... 62

8.1 General ................................................................................................................. 62

8.2 Transportation, handling and installation ............................................................... 62

8.3 Maintenance ......................................................................................................... 63

8.3.1 General ......................................................................................................... 63

8.3.2 Scheduled inspections ................................................................................... 63

Figure 1 – Chordwise (flatwise, edgewise) coordinate system ............................................... 11

Figure 2 – Rotor (flapwise, lead-lag) coordinate system ........................................................ 12

Figure 3 – The building block approach ................................................................................. 13

Figure 4 – Typical process for design and analytical evaluation of blade ............................... 15

Figure 5 – Application of limit states design approach for blade verification .......................... 16

Table 1 – Typical manufacturing effects ................................................................................ 33

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– 4 – IEC 61400-5:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –
Part 5: Wind turbine blades
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

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6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61400-5 has been prepared by IEC technical committee 88: Wind

energy generation systems.
The text of this International Standard is based on the following documents:
FDIS Report on voting
88/759/FDIS 88/767/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

Future standards in this series will carry the new general title as cited above. Titles of existing

standards in this series will be updated at the time of the next edition.
---------------------- Page: 6 ----------------------
IEC 61400-5:2020 © IEC 2020 – 5 –

A list of all parts of the IEC 61400 series, under the general title Wind energy generation

systems, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 7 ----------------------
– 6 – IEC 61400-5:2020 © IEC 2020
INTRODUCTION

The blades of a wind turbine rotor are generally regarded as one of the most critical

components of the wind turbine system. In this International Standard, a minimum set of

requirements for the design and manufacturing of wind turbine blades are defined.

An approach to a structural design process for the blade is set forth in the general areas of

blade characteristics, aerodynamic design, material requirements and structural design.

Furthermore, in order to efficiently facilitate the transfer of a blade design to the production

environment, this document includes demands for designing for manufacturing.

The requirements for structural design of the wind turbine blade have been developed in a

manner to reward innovation, validation, quality and testing. Specifically, the designer will be

able claim lower partial safety factors based on, among other items, the diligence of the

validation of models and the correlation to testing results.

To ensure a production environment that can facilitate the manufacturing of a blade in

accordance with the design, the manufacturing requirements included in this document

provide a minimum basis for a quality management system and workshop requirements. In

addition, requirements for blade handling, operation and maintenance are described in the

close of this document.
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IEC 61400-5:2020 © IEC 2020 – 7 –
WIND ENERGY GENERATION SYSTEMS –
Part 5: Wind turbine blades
1 Scope

This part of IEC 61400 specifies requirements to ensure the engineering integrity of wind

turbine blades as well as an appropriate level of operational safety throughout the design

lifetime. It includes requirements for:
• aerodynamic and structural design,
• material selection, evaluation and testing,
• manufacture (including associated quality management),
• transportation, installation, operation and maintenance of the blades.
The purpose of this document is to provide a technical reference for designers,

manufacturers, purchasers, operators, third party organizations and material suppliers, as

well as to define requirements for certification.

With respect to certification, this document provides the detailed basis for fulfilling the current

requirements of the IECRE system, as well as other IEC standards relevant to wind turbine

blades. When used for certification, the applicability of each portion of this document should

be determined based on the extent of certification, and associated certification modules per

the IECRE system.

The rotor blade is defined as all components integrated in the blade design, excluding

removable bolts in the blade root connection and support structures for installation.

This document is intended to be applied to rotor blades for all wind turbines. For rotor blades

used on small wind turbines according to IEC 61400-2, the requirements in that document are

applicable.

At the time this document was written, most blades were produced for horizontal axis wind

turbines. The blades were mostly made of fiber reinforced plastics. However, most principles

given in this document would be applicable to any rotor blade configuration, size and material.

2 Normative references

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.

IEC 60050-415, International Electrotechnical Vocabulary (IEV) – Part 415: Wind turbine

generator systems
IEC 61400-1, Wind energy generation systems – Part 1: Design requirements
IEC 61400-2, Wind turbines – Part 2: Small wind turbines

IEC 61400-3-1, Wind energy generation systems – Part 3-1: Design requirements for fixed

offshore wind turbines
---------------------- Page: 9 ----------------------
– 8 – IEC 61400-5:2020 © IEC 2020

IEC 61400-3-2, Wind energy generation systems – Part 3-2: Design requirements for floating

offshore wind turbines

IEC 61400-23, Wind turbines – Part 23: Full-scale structural testing of rotor blades

IEC 61400-24, Wind energy generation systems – Part 24: Lightning protection

ISO/IEC 17021-1, Conformity assessment – Requirements for bodies providing audit and

certification of management systems – Part 1: Requirements
ISO 10474, Steel and steel products – Inspection documents
ISO 2394, General principles on reliability for structures
ISO 9000, Quality management systems – Fundamentals and vocabulary
ISO 9001, Quality management systems – Requirements
EN 10204, Metallic products – Types of inspection documents

ISO 16269-6, Statistical interpretation of data – Part 6: Determination of statistical tolerance

intervals
3 Terms and definitions
For the purposes of this document, the terms and definitions given in
IEC 60050-415 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
blade root

that part of the rotor blade that is connected to the hub/pitch-bearing of the rotor

3.2
blade subsystem

integrated set of items that accomplish a defined objective or function within the blade (e.g.,

lightning protection subsystem, aerodynamic braking subsystem, monitoring subsystem,

aerodynamic control subsystem, etc.)
3.3
buckling

instability characterized by a non-linear increase in out of plane deflection with a change in

local compressive load
3.4
characteristic value

value having a prescribed probability of not being attained (i.e. an exceedance probability of

less than or equal to a prescribed amount)
---------------------- Page: 10 ----------------------
IEC 61400-5:2020 © IEC 2020 – 9 –
3.5
chord

length of a reference straight line that joins the leading and trailing edges of a blade aerofoil

cross-section at a given spanwise location
3.6
creep
time-dependant increase in strain under a sustained load
3.7
design limits
maximum or minimum values used in a design
3.8
design loads

loads the blade is designed to withstand, including appropriate partial safety factors

3.9
design properties
material and geometric properties (including design limits)
3.10
edgewise
direction that is parallel to the local chord
3.11
environmental conditions

characteristics of the environment (wind, altitude, temperature, humidity, etc.) which may

affect the wind turbine blade behaviour
3.12
flapwise

direction that is perpendicular to the surface swept by the undeformed rotor blade axis

3.13
flatwise
direction that is perpendicular to the local chord, and spanwise blade axis
3.14
inboard
towards the blade root
3.15
lead-lag

direction that is parallel to the plane of the swept surface and perpendicular to the longitudinal

axis of the undeformed rotor blade
3.16
limit state

state of a structure and the loads acting upon it, beyond which the structure no longer

satisfies the design requirement
3.17
load envelope
collection of maximum design loads in all directions and spanwise positions
---------------------- Page: 11 ----------------------
– 10 – IEC 61400-5:2020 © IEC 2020
3.18
natural frequency
eigen frequency

frequency at which a structure will vibrate when perturbed and allowed to vibrate freely

3.19
partial safety factors

factors that are applied to loads and material strengths to account for uncertainties in the

representative (characteristic) values
3.20
prebend
blade curvature in the flapwise plane in the unloaded condition
3.21
spanwise
direction parallel to the longitudinal axis of a rotor blade
3.22
stiffness

ratio of change of force to the corresponding change in displacement of an elastic body

3.23
strain

ratio of the elongation (or shear displacement) of a material subjected to stress to the original

length of the material
3.24
sweep
blade curvature in the lead-lag plane in the unloaded condition
3.25
twist
spanwise variation in angle of the chord lines of blade cross-sections
3.26
critical to quality
CTQ

process or design value that is measurable and specifies critical acceptance criteria

4 Notation
4.1 Symbols
F load
F design value for the load
F characteristic value for the load
R resistance of material or structure against the corresponding limit state
R characteristic material resistance
PSF Partial Safety Factor
S() function for structural response to the load
T glass transition temperature
p (−) negative Puck inclination parameter
p (+) positive Puck inclination parameter
---------------------- Page: 12 ---
...

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