EN 61400-13:2016

SLOVENSKI STANDARD
01-junij-2016
Vetrne turbine - 13. del: Meritve mehanskih obremenitev (IEC 61400-13:2015)
Wind turbines - Part 13: Measurement of mechanical loads (IEC 61400-13:2015)
Ta slovenski standard je istoveten z: EN 61400-13:2016
ICS:
27.180 Vetrne elektrarne Wind turbine energy systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 61400-13

NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2016
ICS 27.180
English Version
Wind turbines - Part 13: Measurement of mechanical loads
(IEC 61400-13:2015)
Éoliennes - Partie 13: Mesurage des charges mécaniques Windenergieanlagen - Teil 13: Messung von mechanischen
(IEC 61400-13:2015) Lasten
(IEC 61400-13:2015)
This European Standard was approved by CENELEC on 2016-01-25. 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
© 2016 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 61400-13:2016 E
European foreword
The text of document 88/511/CDV, future edition 1 of IEC 61400-13, prepared by IEC/TC 88 "Wind
turbines" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
(dop) 2016-10-25
• 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) 2019-01-25
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 61400-13:2015 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 61400-12-2 NOTE Harmonized as EN 61400-12-2.
IEC 61400-22 NOTE Harmonized as EN 61400-22.
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 Series International Electrotechnical Vocabulary - -
IEC 61400-1 2005 Wind turbines - EN 61400-1 2005
Part 1: Design requirements
IEC 61400-12-1 -  Wind turbines - EN 61400-12-1 -
Part 12-1: Power performance
measurements of electricity producing
wind turbines
ISO/IEC Guide 98-3 -  Uncertainty of measurement - - -
Part 3: Guide to the expression of
uncertainty in measurement
IEC 61400-13 ®
Edition 1.0 2015-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind turbines –
Part 13: Measurement of mechanical loads

Éoliennes –
Partie 13: Mesurage des charges mécaniques

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-3087-9

– 2 – IEC 61400-13:2015 © IEC 2015
CONTENTS
FOREWORD . 8
INTRODUCTION . 10
1 Scope . 11
2 Normative references . 11
3 Terms and definitions . 11
4 Symbols, units and abbreviations . 14
5 General . 16
5.1 Document structure . 16
5.2 Safety during testing . 17
6 Test requirements . 17
6.1 General . 17
6.2 Test site requirements . 17
6.3 Measurement load cases . 17
6.3.1 General . 17
6.3.2 MLCs during steady-state operation . 18
6.3.3 MLCs during transient events . 18
6.3.4 MLCs for dynamic characterization . 19
6.3.5 Capture matrices . 20
6.4 Quantities to be measured . 23
6.4.1 General . 23
6.4.2 Load quantities . 23
6.4.3 Meteorological quantities . 25
6.4.4 Wind turbine operation quantities . 25
6.5 Turbine configuration changes . 26
7 Instrumentation . 27
7.1 Load quantities . 27
7.1.1 Types of sensors . 27
7.1.2 Choice of sensor location . 27
7.1.3 Measurement of blade root bending moments . 27
7.1.4 Blade bending moment distribution . 28
7.1.5 Blade torsion frequency/damping . 28
7.1.6 Measurement of rotor yaw and tilt moment . 28
7.1.7 Measurement of the rotor torque . 28
7.1.8 Measurement of tower base bending . 28
7.1.9 Tower top bending moments . 28
7.1.10 Tower mid bending moments . 29
7.1.11 Tower torque . 29
7.1.12 Tower top acceleration . 29
7.1.13 Pitch actuation loads (on hub side of pitch bearing) . 29
7.2 Meteorological quantities . 29
7.2.1 Measurement and installation requirements . 29
7.2.2 Icing potential . 29
7.2.3 Atmospheric stability . 29
7.3 Wind turbine operation quantities . 30
7.3.1 Electrical power . 30

IEC 61400-13:2015 © IEC 2015 – 3 –
7.3.2 Rotor speed or generator speed . 30
7.3.3 Yaw misalignment . 30
7.3.4 Rotor azimuth angle. 30
7.3.5 Pitch position . 30
7.3.6 Pitch speed . 30
7.3.7 Brake moment . 30
7.3.8 Wind turbine status . 30
7.3.9 Brake status . 30
7.4 Data acquisition system . 31
7.4.1 General . 31
7.4.2 Resolution . 31
7.4.3 Anti-aliasing. 31
8 Determination of calibration factors . 31
8.1 General . 31
8.2 Calibration of load channels . 32
8.2.1 General . 32
8.2.2 Blade bending moments . 33
8.2.3 Main shaft moments . 33
8.2.4 Tower bending moments . 34
8.2.5 Tower torque . 34
8.3 Calibration of non-load channels . 35
8.3.1 Pitch angle . 35
8.3.2 Rotor azimuth angle. 35
8.3.3 Yaw angle. 35
8.3.4 Wind direction. 35
8.3.5 Pitch actuation loads . 35
8.3.6 Brake moment . 36
9 Data verification . 36
9.1 General . 36
9.2 Verification checks . 36
9.2.1 General . 36
9.2.2 Blade moments . 37
9.2.3 Main shaft . 38
9.2.4 Tower . 38
10 Processing of measured data . 39
10.1 General . 39
10.2 Fundamental load quantities . 39
10.3 Load quantities for larger turbines . 39
10.4 Wind speed trend detection . 39
10.5 Statistics . 40
10.6 Rainflow counting . 40
10.7 Cumulative rainflow spectrum . 40
10.8 Damage equivalent load. 40
10.9 Wind speed binning . 41
10.10 Power spectral density . 42
11 Uncertainty estimation . 42
12 Reporting. 42
Annex A (informative) Example co-ordinate systems . 46

– 4 – IEC 61400-13:2015 © IEC 2015
A.1 General . 46
A.2 Blade co-ordinate system . 46
A.3 Hub co-ordinate system . 46
A.4 Nacelle co-ordinate system . 47
A.5 Tower co-ordinate system . 48
A.6 Yaw misalignment . 49
A.7 Cone angle and tilt angle . 49
A.8 Rotor azimuth angle . 50
A.9 Blade pitch angle . 50
Annex B (informative) Procedure for the evaluation of uncertainties in load
measurements on wind turbines . 51
B.1 List of symbols . 51
B.2 General procedure . 52
B.2.1 Standard uncertainty . 52
B.2.2 Analytical combination of standard uncertainties . 53
B.2.3 Total uncertainty . 54
B.3 Uncertainties of binned averaged values . 55
B.3.1 General . 55
B.3.2 Uncertainty of calibration and signal . 55
B.3.3 Uncertainty of the bin scatter . 55
B.3.4 Uncertainty of the x-axis quantity . 55
B.3.5 Uncertainty of bin averaged mean values . 55
B.4 Standard uncertainty of DEL and load spectra . 56
B.5 Examples of an uncertainty evaluation . 56
B.5.1 Example for analytical shunt calibration of tower torque . 56
B.6 Determination and use of calibration matrix . 63
B.6.1 Determination of the calibration matrix . 63
B.6.2 Use of the calibration matrix . 64
B.6.3 Time series . 65
Annex C (informative) Sample presentation of mechanical load measurements and
analysis . 67
C.1 General . 67
Annex D (informative)  Recommendations for offshore measurements . 79
Annex E (informative) Load model validation . 81
E.1 General . 81
E.2 Methods for loads comparison . 82
E.2.1 Statistical binning . 82
E.2.2 Spectral functions . 83
E.2.3 Fatigue spectra . 84
E.2.4 Point by point . 84
Annex F (informative) Methods for identification of wind speed trends . 86
F.1 List of symbols . 86
F.2 General . 86
F.3 Trend identification methods . 87
F.4 Ongoing procedure . 91
Annex G (informative) Data acquisition considerations . 92
G.1 Data acquisition system . 92
G.1.1 General . 92

IEC 61400-13:2015 © IEC 2015 – 5 –
G.1.2 Resolution . 92
G.1.3 Sampling model and filtering . 93
G.1.4 Other considerations . 95
Annex H (informative) Load calibration . 96
H.1 General . 96
H.2 Gravity load calibration of the blade bending . 96
H.3 Analytical calibration of the tower bending moments . 97
H.4 External load calibration of the rotor torque . 98
Annex I (informative) Temperature drift . 99
I.1 General . 99
I.2 Known issues . 99
I.3 Recommendations . 100
Annex J (informative) Mechanical load measurements on vertical axis wind turbines . 101
J.1 General . 101
J.2 Terms and definitions . 101
J.3 Coordinate systems . 101
J.4 Quantities to be measured . 102
J.4.1 Fundamental loads . 102
J.5 Measurements . 103
J.5.1 Measurement of blade attachment bending moments . 103
J.5.2 Blade mid-span bending moment . 103
J.5.3 Blade modal frequency/damping . 103
J.5.4 Connecting strut bending moment. 103
J.5.5 Connecting strut axial force . 104
J.5.6 Connecting strut modal frequency/damping . 104
J.5.7 Rotor shaft torque . 104
J.5.8 Tower normal bending . 104
Bibliography . 105

Figure 1 – Fundamental wind turbine loads: tower base, rotor and blade loads . 24
Figure A.1 – Blade co-ordinate system . 46
Figure A.2 – Hub co-ordinate system . 47
Figure A.3 – Nacelle co-ordinate system . 48
Figure A.4 – Tower co-ordinate system . 48
Figure A.5 – Yaw misalignment . 49
Figure A.6 – Cone angle and tilt angle . 49
Figure B.1 – Explanation of used symbols . 61
Figure C.1 – Hub-height wind speed as a function of time . 67
Figure C.2 – Hub-height turbulence intensity as a function of hub-height wind speed . 68
Figure C.3 – Turbulence intensity trending as a function of hub-height wind speed . 68
Figure C.4 – Global capture matrix with all loads channels operating . 69
Figure C.5 – IEC example turbine at 9,1 m/s – Wind turbine operational and
meteorological quantities . 70
Figure C.6 – IEC example turbine at 9,1 m/s – Major load components . 71
Figure C.7 – 10-minute statistics for blade 1 root edge bending . 72
Figure C.8 – Power spectral density of blade 1 root edge bending . 73

– 6 – IEC 61400-13:2015 © IEC 2015
Figure C.9 – Cumulative rainflow spectrum for blade 1 root edge bending during test
period . 75
Figure C.10 – IEC example turbine normal shutdown at 9,5 m/s – Wind turbine
operational and meteorological quantities . 77
Figure C.11 – IEC example turbine normal shutdown at 9,5 m/s – Major load
components . 78
Figure D.1 – Example of wave spectrum and monopile response . 79
Figure D.2 – Example of wave spectrum . 80
Figure E.1 – Measured data . 82
Figure E.2 – Simulated data . 82
Figure E.3 – Comparison of wind speed binned averaged 10 min. statistics . 82
Figure E.4 – Comparison of 1 Hz equivalent loads . 83
Figure E.5 – Comparison of 1 Hz equivalent loads (wind speed binned) . 83
Figure E.6 – Comparison of PSD functions . 83
Figure E.7 – Comparison of fatigue spectra . 84
Figure E.8 – Point by point comparison of wind speed time histories . 85
Figure E.9 – Point by point comparison of load time histories. 85
Figure F.1 – Comparison of measured wind speed (v ), smoothing-filtered wind
meas
speed (v ) and resulting trend-free wind speed (v ) . 87
filt HP
Figure F.2 – Differences of turbulence intensities calculated with un-filtered and filtered
wind speed versus mean measured wind speed . 89
Figure F.3 – Ratio of turbulence intensities calculated with un-filtered and filtered wind
speed versus mean measured wind speed . 90
Figure G.1 – Anti-aliasing check . 93
Figure I.1 – Observed scatter in the original 10-min average values of the blade edge
moment together with the same signal after temperature compensation in dark blue . 99
Figure I.2 – Linear regression through the offsets derived from the different calibration
runs . 100
Figure J.1 – Darrieus style VAWT . 102
Figure J.2 – Helical Darrieus style VAWT . 102

Table 1 – MLCs during steady-state operation related to the DLCs defined in
IEC 61400-1 . 18
Table 2 – Measurement of transient load cases related to the DLCs defined in
IEC 61400-1 . 19
Table 3 – MLCs for dynamic characterization . 19
Table 4 – Capture matrix for normal power production for stall controlled wind turbines . 21
Table 5 – Capture matrix for normal power production for non stall controlled wind
turbines . 22
Table 6 – Capture matrix for parked condition . 22
Table 7 – Capture matrix for normal transient events . 23
Table 8 – Capture matrix for other than normal transient events . 23
Table 9 – Wind turbine fundamental load quantities . 24
Table 10 – Additional load quantities for turbines with a rated power output greater
than 1 500 kW and rotor diameter greater than 75 m . 25
Table 11 – Meteorological quantities . 25

IEC 61400-13:2015 © IEC 2015 – 7 –
Table 12 – Wind turbine operation quantities . 26
Table 13 – Summary of suitable calibration methods . 32
Table B.1 – Uncertainty components . 56
Table B.2 – Values and uncertainties for the calculation . 60
Table C.1 – Binned data for blade 1 root edge bending . 74
Table C.2 – Transient capture matrix for normal start-up and shutdown . 76
Table C.3 – Brief statistical description for normal shutdown for IEC example turbine
at 9,5 m/s . 76
Table G.1 – Wind turbine significant frequencies . 94
Table G.2 – Sampling ratio . 94
Table J.1 – Minimum recommendations for VAWT fundamental load quantities . 103

– 8 – IEC 61400-13:2015 © IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND TURBINES –
Part 13: Measurement of mechanical loads

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,
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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.
This International Standard IEC 61400-13 has been prepared by IEC technical committee 88:
Wind turbines.
This standard replaces IEC TS 61400-13 published in 2001. This first edition constitutes a
technical revision and transition from technical specification to International Standard.
This first edition includes the following changes with respect to the technical specification:
a) scope of the document focused to load measurements for the purpose of model validation;
b) number of measurement load cases to match the new scope reduced;
c) capture matrix requirements to match the new scope reduced;
d) requirements to address the state of the art technology updated.

IEC 61400-13:2015 © IEC 2015 – 9 –
The text of this standard is based on the following documents:
CDV Report on voting
88/511/CDV 88/554/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 website 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.
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.
– 10 – IEC 61400-13:2015 © IEC 2015
INTRODUCTION
In the process of structural design of a wind turbine, thorough understanding about, and
accurate quantification of, the loading is of utmost importance.
In the design stage, loads can be predicted with aeroelastic models and codes. However,
such models have their shortcomings and uncertainties, and they always need to be validated
by measurement.
Mechanical load measurements can be used both as the basis for design and as the basis for
certification. Design aspects for wind turbines are covered by IEC 61400-1 whilst certification
procedures are described in IEC 61400-22. This standard is aimed at the test institute, the
turbine manufacturer and the certifying body and clearly defines the minimum requirements
for a mechanical loads test resulting in consistent, high quality reproducible test results.

IEC 61400-13:2015 © IEC 2015 – 11 –
WIND TURBINES –
Part 13: Measurement of mechanical loads

1 Scope
This part of the IEC 61400 describes the measurement of fundamental structural loads on
wind turbines for the purpose of the load simulation model validation. The standard prescribes
the requirements and recommendations for site selection, signal selection, data acquisition,
calibration, data verification, measurement load cases, capture matrix, post-processing,
uncertainty determination and reporting. Informative annexes are also provided to improve
understanding of testing methods.
The methods described in this document can also be used for mechanical loads
measurements for other purposes such as obtaining a measured statistical representation of
loads, direct measurements of the design loads, safety and function testing, or measurement
of component loads. If these methods are used for an alternative objective or used for an
unconventional wind turbine design, the required signals, measurement load cases, capture
matrix, and post processing methods should be evaluated and if needed adjusted to fit the
objective.
These methods are intended for onshore electricity-generating, horizontal-axis wind turbines
(HAWTs) with rotor swept areas of larger than 200 m . However, the methods described may
be applicable to other wind turbines (for example, small wind turbines, ducted wind turbines,
vertical axis wind turbines).
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 (all parts), International Electrotechnical Vocabulary (available at
)
IEC 61400-1:2005, Wind turbines – Part 1: Design requirements
IEC 61400-12-1, Wind turbines – Part 12-1: Power performance measurements of electricity
producing wind turbines
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement
3 Terms and definitions
For the purposes of this document, the terms and definitions related to wind turbine systems
or wind energy in general of IEC 60050-415 as well as the following apply.
3.1
blade
rotating aerodynamically active part of the rotor

– 12 – IEC 61400-13:2015 © IEC 2015
3.2
blade root
that part of the blade that is connected to the hub of the rotor
3.3
brake status
status indicating if the brake is applied or not
3.4
calibration
determination of the transfer function and its coefficients from sensor output to the physical
value
3.5
capture matrix
organization of the measured time series according to their mean wind speeds and turbulence
intensities
3.6
chord line
imaginary straight line that joins the leading and trailing edges of a blade airfoil cross-section
3.7
cut-in wind speed
lowest wind speed at hub height at which the wind turbine starts to produce power in the case
of steady wind without turbulence
3.8
cut-out wind speed
highest wind speed at hub height at which the wind turbine is designed to produce power in
the case of steady wind without turbulence
3.9
design loads
loads that the turbine is designed to withstand
Note 1 to entry: They are obtained by applying the appropriate partial lo
...