Wind turbines - Part 23: Full-scale structural testing of rotor blades

Is a technical specification providing guidelines for the full-scale structural testing of wind turbine blades and for the interpretation or evaluation of results, as a possible part of a design verification of the integrity of the blade. Includes static strength tests, fatigue tests, and other tests determining blade properties. This publication is of high relevance for Smart Grid.

Windenergieanlagen - Teil 23: Rotorblätter - Experimentelle Strukturprüfung

Éoliennes - Partie 23: Essais en vraie grandeur des structures des pales de rotor

l'IEC 61400-23:2014 définit les exigences concernant les essais en vraie grandeur des structures des pales d'éolienne, ainsi que l'interprétation et l'évaluation des résultats d'essai obtenus. La norme cible les aspects des essais liés à une évaluation de l'intégrité des pales, et s'adresse aux fabricants et aux chercheurs tiers. La présente norme prend en considération les essais suivants: - essais de charge statique; - essais de fatigue; - essais de charge statique après essais de fatigue; - essais déterminant d'autres propriétés des pales.

Sistemi generatorjev za vetrne turbine - 23. del: Popolno strukturno preskušanje krakov rotorja (IEC 61400-23:2014)

Standard EN IEC 61400-23 določa zahteve za popolno strukturno preskušanje krakov rotorja lopatic vetrne turbine ter za razlago in vrednotenje rezultatov preskusa. Standard se osredotoča na vidike testiranja, povezane z oceno celovitosti krakov, ki jih uporabljajo proizvajalci in drugi raziskovalci. Standard zajema naslednje preskuse: - preskusi statične obremenitve; - preskus utrujenosti; - preskusi statične obremenitve po preskusu utrujenosti; - preskusi za določanje drugih lastnosti krakov. Namen testov je potrditi sprejemljivo stopnjo verjetnosti, da celotna populacija tipa krakov izpolnjuje konstrukcijske predpostavke. Predvideva se, da so podatki, potrebni za določanje parametrov preskusov, na voljo in da temeljijo na standardu za konstrukcijske zahteve za vetrne turbine, kot je IEC 61400-1 ali enakovrednih standardih. Konstrukcijske obremenitve in podatki o materialu krakov se upoštevajo kot izhodišča za določanje in ocenjevanje preskusnih bremen. Vrednotenje konstrukcijske obremenitve glede na dejanske obremenitve vetrnih turbin je zunaj področja uporabe tega standarda. V času nastajanja tega standarda je bilo izvedeno polno strukturno preskušanje krakov vetrnih turbin s horizontalno osjo. Kraki so v večji meri izdelani iz polimernih materialov, ojačanih z vlakni, in lesa/epoksidne smole. Kljub temu se večina načel lahko uporabi za poljubno konfiguracijo vetrnih turbin, ne glede na velikost in material.

General Information

Status
Published
Publication Date
22-May-2014
Technical Committee
Drafting Committee
Current Stage
6060 - Document made available
Due Date
23-May-2014
Completion Date
23-May-2014

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SLOVENSKI STANDARD
SIST EN 61400-23:2014
01-september-2014
Sistemi generatorjev za vetrne turbine - 23. del: Popolno strukturno preskušanje
krakov rotorja (IEC 61400-23:2014)

Wind turbine generator systems - Part 23: Full-scale structural testing of rotor blades

Ta slovenski standard je istoveten z: EN 61400-23:2014
ICS:
27.180 Sistemi turbin na veter in Wind turbine systems and
drugi alternativni viri energije other alternative sources of
energy
SIST EN 61400-23:2014 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61400-23:2014
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SIST EN 61400-23:2014
EUROPEAN STANDARD EN 61400-23
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2014
ICS 27.180
English Version
Wind turbines - Part 23: Full-scale structural testing
of rotor blades
(IEC 61400-23:2014)

Éoliennes - Partie 23: Essais en vraie grandeur Windenergieanlagen - Teil 23: Rotorblätter -

des structures des pales de rotor Experimentelle Strukturprüfung
(CEI 61400-23:2014) (IEC 61400-23:2014)

This European Standard was approved by CENELEC on 2014-05-13. 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 61400-23:2014 E
---------------------- Page: 3 ----------------------
SIST EN 61400-23:2014
EN 61400-23:2014 - 2 -
Foreword

The text of document 88/420/CDV, future edition 1 of IEC 61400-23, prepared by IEC TC 88 "Wind

turbines" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN 61400-

23:2014.
The following dates are fixed:
(dop) 2015-02-13
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2017-05-13
standards conflicting with the
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 [and/or CEN] shall not be held responsible for identifying any or all such patent

rights.
Endorsement notice

The text of the International Standard IEC 61400-23:2014 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 standards indicated:

IEC 61400-22 NOTE Harmonised as EN 61400-22 (not modified).
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SIST EN 61400-23:2014
- 3 - EN 61400-23:2014
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When 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.cenelec.eu
Publication Year Title EN/HD Year
IEC 60050-415 1999 International Electrotechnical Vocabulary - - -
Part 415: Wind turbine generator systems
IEC 61400-1 2005 Wind turbines - EN 61400-1 2005
Part 1: Design requirements

ISO/IEC 17025 2005 General requirements for the competence of EN ISO/IEC 17025 2005

testing and calibration laboratories
ISO 2394 1986 General principles on reliability for structures - -
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SIST EN 61400-23:2014
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SIST EN 61400-23:2014
IEC 61400-23
Edition 1.0 2014-04
INTERNATIONAL
STANDARD
colour
inside
Wind turbines –
Part 23: Full-scale structural testing of rotor blades
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
ICS 27.180 ISBN 978-2-8322-1506-7

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 7 ----------------------
SIST EN 61400-23:2014
– 2 – IEC 61400-23:2014 © IEC 2014
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 9

4 Notation ......................................................................................................................... 12

4.1 Symbols ................................................................................................................ 12

4.2 Greek symbols ...................................................................................................... 12

4.3 Subscripts ............................................................................................................. 12

4.4 Coordinate systems .............................................................................................. 12

5 General principles ......................................................................................................... 13

5.1 Purpose of tests .................................................................................................... 13

5.2 Limit states ........................................................................................................... 14

5.3 Practical constraints ............................................................................................. 14

5.4 Results of test ....................................................................................................... 14

6 Documentation and procedures for test blade ................................................................ 15

7 Blade test program and test plans ................................................................................. 16

7.1 Areas to be tested ................................................................................................. 16

7.2 Test program ........................................................................................................ 16

7.3 Test plans ............................................................................................................. 16

7.3.1 General ......................................................................................................... 16

7.3.2 Blade description ........................................................................................... 16

7.3.3 Loads and conditions ..................................................................................... 17

7.3.4 Instrumentation .............................................................................................. 17

7.3.5 Expected test results ..................................................................................... 17

8 Load factors for testing .................................................................................................. 17

8.1 General ................................................................................................................. 17

8.2 Partial safety factors used in the design ................................................................ 17

8.2.1 General ......................................................................................................... 17

8.2.2 Partial factors on materials ............................................................................ 17

8.2.3 Partial factors for consequences of failure ..................................................... 18

8.2.4 Partial factors on loads .................................................................................. 18

8.3 Test load factors ................................................................................................... 18

8.3.1 Blade to blade variation ................................................................................. 18

8.3.2 Possible errors in the fatigue formulation ....................................................... 18

8.3.3 Environmental conditions ............................................................................... 19

8.4 Application of load factors to obtain the target load ............................................... 19

9 Test loading and test load evaluation ............................................................................. 20

9.1 General ................................................................................................................. 20

9.2 Influence of load introduction ................................................................................ 20

9.3 Static load testing ................................................................................................. 20

9.4 Fatigue load testing .............................................................................................. 21

10 Test requirements.......................................................................................................... 22

10.1 General ................................................................................................................. 22

10.1.1 Test records .................................................................................................. 22

10.1.2 Instrumentation calibration............................................................................. 22

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SIST EN 61400-23:2014
IEC 61400-23:2014 © IEC 2014 – 3 –

10.1.3 Measurement uncertainties ............................................................................ 22

10.1.4 Root fixture and test stand requirements ....................................................... 22

10.1.5 Environmental conditions monitoring ............................................................. 22

10.1.6 Deterministic corrections ............................................................................... 23

10.2 Static test ............................................................................................................. 23

10.2.1 General ......................................................................................................... 23

10.2.2 Static load test............................................................................................... 23

10.2.3 Strain measurement ...................................................................................... 24

10.2.4 Deflection measurement ................................................................................ 24

10.3 Fatigue test ........................................................................................................... 24

10.4 Other blade property tests .................................................................................... 24

10.4.1 Blade mass and center of gravity ................................................................... 24

10.4.2 Natural frequencies ....................................................................................... 25

10.4.3 Optional blade property tests ......................................................................... 25

11 Test results evaluation................................................................................................... 25

11.1 General ................................................................................................................. 25

11.2 Catastrophic failure ............................................................................................... 25

11.3 Permanent deformation, loss of stiffness or change in other blade properties ....... 26

11.4 Superficial damage ............................................................................................... 26

11.5 Failure evaluation ................................................................................................. 26

12 Reporting ...................................................................................................................... 26

12.1 General ................................................................................................................. 26

12.2 Test report content................................................................................................ 27

12.3 Evaluation of test in relation to design requirements ............................................. 27

Annex A (informative) Guidelines for the necessity of renewed static and fatigue

testing .................................................................................................................................. 28

Annex B (informative) Areas to be tested ............................................................................. 29

Annex C (informative) Effects of large deflections and load direction ................................... 30

Annex D (informative) Formulation of test load .................................................................... 31

D.1 Static target load................................................................................................... 31

D.2 Fatigue target load ................................................................................................ 31

D.3 Sequential single-axial, single location .................................................................. 34

D.4 Multi axial single location ...................................................................................... 34

Annex E (informative) Differences between design and test load conditions ......................... 36

E.1 General ................................................................................................................. 36

E.2 Load introduction .................................................................................................. 36

E.3 Bending moments and shear ................................................................................. 36

E.4 Flapwise and lead-lag combinations ...................................................................... 36

E.5 Radial loads .......................................................................................................... 37

E.6 Torsion loads ........................................................................................................ 37

E.7 Environmental conditions ...................................................................................... 37

E.8 Fatigue load spectrum and sequence .................................................................... 37

Annex F (informative) Determination of number of load cycles for fatigue tests .................... 38

F.1 General ................................................................................................................. 38

F.2 Background .......................................................................................................... 38

F.3 The approach used ............................................................................................... 38

Bibliography .......................................................................................................................... 43

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SIST EN 61400-23:2014
– 4 – IEC 61400-23:2014 © IEC 2014

Figure 1 – Chordwise (flatwise, edgewise) coordinate system ............................................... 13

Figure 2 – Rotor (flapwise, lead-lag) coordinate system ........................................................ 13

Figure C.1 – Applied loads effects due to blade deformation and angulation ........................ 30

Figure D.1 – Polar plot of the load envelope from a typical blade .......................................... 31

Figure D.2 – Design FSF ....................................................................................................... 33

Figure D.3 – Area where design FSF is smaller than 1,4 (critical area) .................................. 33

Figure D.4 – rFSF and critical areas, sequential single-axial test ........................................... 34

Figure D.5 – rFSF and critical area, multi axial test ............................................................... 35

Figure E.1 – Difference of moment distribution for target and actual test load ....................... 36

Figure F.1 – Simplified Goodman diagram ............................................................................ 39

Figure F.2 – Test load factor γ for different number of load cycles in the test ..................... 42

Table 1 – Recommended values for γ for different number of load cycles ........................... 18

Table A.1 – Examples of situations typically requiring or not requiring renewed testing ........ 28

Table F.1 – Recommended values for γ for different number of load cycles ........................ 38

Table F.2 – Expanded recommended values for γ for different number of load cycles ....... 41

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SIST EN 61400-23:2014
IEC 61400-23:2014 © IEC 2014 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND TURBINES –
Part 23: Full-scale structural testing of rotor 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

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

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

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

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 61400-23 has been prepared by IEC technical committee 88: Wind

turbines.

This first edition cancels and replaces IEC TS 61400-23, published in 2001. It constitutes a

technical revision.

This edition includes the following significant technical changes with respect to

IEC TS 61400-23:
a) description of load based testing only;
b) condensation to describe the general principles and demands.
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SIST EN 61400-23:2014
– 6 – IEC 61400-23:2014 © IEC 2014
The text of this standard is based on the following documents:
CDV Report on voting
88/420/CDV 88/448/RVC

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

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

A list of all parts in the IEC 61400 series, published under the general title Wind turbines, can

be found on the IEC website.

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

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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.
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SIST EN 61400-23:2014
IEC 61400-23:2014 © IEC 2014 – 7 –
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 standard, the demands for full-scale structural

testing related to certification are defined as well as the interpretation and evaluation of test

results.

Specific testing methods or set-ups for testing are not demanded or included as full-scale

blade testing methods historically have developed independently in different countries and

laboratories.

Furthermore, demands for tests determining blade properties are included in this standard in

order to validate some vital design assumptions used as inputs for the design load

calculations.

Any of the requirements of this standard may be altered if it can be suitably demonstrated that

the safety of the system is not compromised.

The standard is based on IEC TS 61400-23 published in 2001. Compared to the TS, this

standard only describes load based testing and is condensed to describe the general

principles and demands.
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SIST EN 61400-23:2014
– 8 – IEC 61400-23:2014 © IEC 2014
WIND TURBINES –
Part 23: Full-scale structural testing of rotor blades
1 Scope

This part of IEC 61400 defines the requirements for full-scale structural testing of wind turbine

blades and for the interpretation and evaluation of achieved test results. The standard

focuses on aspects of testing related to an evaluation of the integrity of the blade, for use by

manufacturers and third party investigators.
The following tests are considered in this standard:
• static load tests;
• fatigue tests;
• static load tests after fatigue tests;
• tests determining other blade properties.

The purpose of the tests is to confirm to an acceptable level of probability that the whole

population of a blade type fulfils the design assumptions.

It is assumed that the data required to define the parameters of the tests are available and

based on the standard for design requirements for wind turbines such as IEC 61400-1 or

equivalent. Design loads and blade material data are considered starting points for

establishing and evaluating the test loads. The evaluation of the design loads with respect to

the actual loads on the wind turbines is outside the scope of this standard.

At the time this standard was written, full-scale tests were carried out on blades of horizontal

axis wind turbines. The blades were mostly made of fibre reinforced plastics and wood/epoxy.

However, most principles would be applicable to any wind turbine configuration, size and

material.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.

IEC 60050-415:1999, International Electrotechnical Vocabulary – Part 415: Wind turbine

generator systems
IEC 61400-1:2005, Wind turbines – Part 1: Design requirements

ISO/IEC 17025:2005, General requirements for the competence of testing and calibration

laboratories
ISO 2394:1998, General principles on reliability for structures
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SIST EN 61400-23:2014
IEC 61400-23:2014 © IEC 2014 – 9 –
3 Terms and definitions

For the purposes of this document, the terms and definitions related to wind turbines or wind

energy given in IEC 60050-415 and the following apply.
3.1
actuator

device that can be controlled to apply a constant or varying force and displacement

3.2
blade root
that part of the rotor blade that is connected to the hub of the rotor
3.3
blade subsystem

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

lightning protection subsystem, aerodynamic braking subsystem, monitoring subsystem,

aerodynamic control subsystem, etc.)
3.4
buckling

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

local compressive load
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
constant amplitude loading

during a fatigue test, the application of load cycles with a constant amplitude and mean value

3.7
creep
time-dependant increase in strain under a sustained load
3.8
design loads

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

3.9
edgewise
direction that is parallel to the local chord
SEE: 4.4.
3.10
elastic axis

the line, lengthwise of the blade, along which transverse loads are applied in order to produce

bending only, with no torsion at any section

Note 1 to entry: Strictly speaking, no such line exists except for a few conditions of loading. Usually the elastic

axis is assumed to be the line that passes through the elastic center of every section. This definition is not

applicable for blades with bend-twist coupling.
3.11
fatigue formulation
methodology by which the fatigue life is estimated
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SIST EN 61400-23:2014
– 10 – IEC 61400-23:2014 © IEC 2014
3.12
fatigue test
test in which a cyclic load of constant or varying amplitude is applied to th
...

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