SIST EN 61400-12-2:2013

SLOVENSKI STANDARD
SIST EN 61400-12-2:2013
01-september-2013
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Wind turbines - Part 12-2: Power performance of electricity producing wind turbines
based on nacelle anemometry
Windturbinen - Teil 12-2: Leistungsverhalten von Elektrizität erzeugenden Windturbinen
mit Gondelanemometer
Eoliennes - Partie 12-2: Performance de puissance des éoliennes de production
d'électricité basée sur l'anémométrie de nacelle
Ta slovenski standard je istoveten z: EN 61400-12-2:2013
ICS:
27.180 Sistemi turbin na veter in Wind turbine systems and
drugi alternativni viri energije other alternative sources of
energy
SIST EN 61400-12-2:2013 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61400-12-2:2013

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SIST EN 61400-12-2:2013

EUROPEAN STANDARD
EN 61400-12-2

NORME EUROPÉENNE
July 2013
EUROPÄISCHE NORM

ICS 27.180


English version


Wind turbines -
Part 12-2: Power performance of electricity-producing wind turbines
based on nacelle anemometry
(IEC 61400-12-2:2013)


Eoliennes -  Windenergieanlagen -
Partie 12-2: Performance de puissance Teil 12-2: Messung des
des éoliennes de production d'électricité Leistungsverhaltens von Elektrizität
basée sur l'anémométrie de nacelle erzeugenden Windturbinen basierend auf
(CEI 61400-12-2:2013) Gondelanemometrie
(IEC 61400-12-2:2013)





This European Standard was approved by CENELEC on 2013-05-02. 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.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels


© 2013 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61400-12-2:2013 E

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SIST EN 61400-12-2:2013
EN 61400-12-2:2013 - 2 -
Foreword
The text of document 88/442/FDIS, future edition 1 of IEC 61400-12-2, prepared by IEC/TC 88 "Wind
turbines" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
EN 61400-12-2:2013.

The following dates are fixed:
(dop) 2014-02-02
• 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) 2016-05-02
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 61400-12-2:2013 was approved by CENELEC as a
European Standard without any modification.

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SIST EN 61400-12-2:2013
- 3 - EN 61400-12-2:2013
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  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60688 1992 Electrical measuring transducers for EN 60688 1992
+ A1 (mod) 1997 converting a.c. electrical quantities to + A1 1999
+ A2 2001 analogue or digital signals + A2 2001


IEC 61400-12-1 2005 Wind turbines - EN 61400-12-1 2006
Part 12-1: Power performance
measurements of electricity producing
wind turbines


IEC 61869-2 - Instrument transformers - EN 61869-2 -
Part 2: Additional requirements for current
transformers


IEC 61869-3 - Instrument transformers - EN 61869-3 -
Part 3: Additional requirements for inductive
voltage transformers


ISO/IEC 17025 - General requirements for the competence of EN ISO/IEC 17025 -
testing and calibration laboratories


ISO/IEC - Uncertainty of measurement - - -
Guide 98-3 Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)


ISO 2533 - Standard atmosphere - -

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SIST EN 61400-12-2:2013

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SIST EN 61400-12-2:2013




IEC 61400-12-2

®


Edition 1.0 2013-03




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Wind turbines –

Part 12-2: Power performance of electricity-producing wind turbines based on

nacelle anemometry




Eoliennes –

Partie 12-2: Performance de puissance des éoliennes de production d'électricité


basée sur l'anémométrie de nacelle













INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX XE


ICS 27.180 ISBN 978-2-83220-658-4



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

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 61400-12-2:2013
– 2 – 61400-12-2 © IEC:2013
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Symbols and units . 13
5 Overview of test method . 16
6 Preparation for performance test . 19
6.1 General . 19
6.2 Wind turbine . 19
6.3 Test site . 19
6.3.1 Terrain classification. 20
6.3.2 RIX indices . 20
6.3.3 Average slope . 21
6.3.4 Determine terrain class . 21
6.3.5 Ridge formations . 22
6.4 Nacelle wind speed transfer function . 23
6.5 Test plan . 23
7 Test equipment . 23
7.1 Electric power . 23
7.2 Wind speed . 24
7.3 Wind direction . 24
7.3.1 Nacelle yaw position sensor . 24
7.3.2 Nacelle wind direction sensor . 25
7.3.3 Wind direction . 25
7.4 Air density . 25
7.5 Rotor speed . 26
7.6 Pitch angle . 26
7.7 Wind turbine status . 26
7.8 Data acquisition. 26
8 Measurement procedure . 27
8.1 General . 27
8.2 Wind turbine operation . 27
8.3 Data system(s) synchronisation . 27
8.4 Data collection . 28
8.5 Data quality check . 28
8.6 Data rejection . 29
8.7 Data correction . 30
8.8 Database . 30
9 Derived results . 31
9.1 Data normalisation . 31
9.1.1 Density correction . 31
9.2 Determination of measured power curve . 32
9.3 Annual energy production (AEP) . 32
9.4 Power coefficient . 33
9.5 Uncertainty analysis . 34

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SIST EN 61400-12-2:2013
61400-12-2 © IEC:2013 – 3 –
10 Reporting format . 34
Annex A (informative) Nacelle instrument mounting . 42
Annex B (normative) Measurement sector procedure . 44
Annex C (normative) Nacelle wind speed transfer function validity procedure . 49
Annex D (normative) Nacelle wind speed transfer function measurement procedure . 51
Annex E (normative) Evaluation of uncertainty in measurement . 58
Annex F (normative) Theoretical basis for determining the uncertainty of
measurement using the method of bins . 62
Annex G (normative) NTF/NPC uncertainty estimates and calculation . 70
Annex H (normative) Allowable anemometry instrument types . 83
Annex I (informative) Results and uncertainty considerations . 85
Annex J (informative) Example multi-turbine NTF/NPC uncertainty calculation . 90
Annex K (informative) Organisation of test, safety and communication . 98
Annex L (informative) NPC and NTF flowchart . 100

Figure 1 – Procedural overview . 18
Figure 2 – Presentation of example data: transfer function resulting from Annex D . 37
Figure 3 – Presentation of example data: nacelle power performance test scatter plots . 38
Figure 4 – Presentation of example data: binned power curve with uncertainty bands . 38
Figure 5 – Presentation of example data: measured power curve and C curve . 39
p
Figure A.1 – Mounting of anemometer on top of nacelle . 43
Figure B.1 – Sectors to exclude due to wakes of neighbouring and operating wind
turbines and significant obstacles . 46
Figure B.2 – Example of the result of a sector self-consistency check . 48
Figure D.1 – Nacelle transfer function for wind speed . 56
Figure J.1 – Impact of multiple turbine testing on measurement uncertainty . 97
Figure J.2 – Impact of multiple turbine testing on sampling uncertainty . 97
Figure L.1 – NPC flowchart . 100
Figure L.2 – NTF flowchart. 101

Table 1 – Slope terrain classification . 21
Table 2 – RIX terrain classification . 22
Table 3 – Final terrain class . 22
Table 4 – Maximum ridge step effects on terrain class . 22
Table 5 – Example of a measured power curve . 40
Table 6 – Example of estimated annual energy production . 41
Table B.1 – Obstacle requirements: relevance of obstacles . 45
Table D.1 – Example of presentation of a measured power curve based on data from
the meteorological mast, for consistency check . 57
Table E.1 – Uncertainty components in nacelle transfer function evaluation . 59
Table E.2 – Uncertainty components in nacelle power curve evaluation . 60
Table E.3 – Uncertainty components in nacelle based absolute wind direction . 61
Table F.1 – Example cancellation sources . 64
Table F.2 – List of category A and B uncertainties for NTF . 64

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SIST EN 61400-12-2:2013
– 4 – 61400-12-2 © IEC:2013
Table F.3 – List of category A and B uncertainties for NPC . 66
Table F.4 – Expanded uncertainties . 69
Table G.1 – Estimates for uncertainty components from site calibration . 70
Table G.2 – Estimates for uncertainty components from NTF measurement . 72
Table G.3 – Estimates for uncertainty components from NPC measurement . 74
Table G.4 – Estimates for u for NPC terrain class . 76
V5,i
Table G.5 – Estimates for uncertainty components for wind direction . 77
Table G.6 – Estimates for contribution factors for site calibration . 78
Table G.7 – Estimates for contribution factors for NTF . 79
Table G.8 – Estimates for contribution factors for NPC . 80
Table J.1 – List of correlated uncertainty components . 91
Table J.2 – Sample AEP and uncertainty data from 3 turbines . 93
Table J.3 – Component uncertainty contribution to AEP uncertainty on turbine 1 . 93
Table J.4 – Combination of uncertainty components across turbines. . 95

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SIST EN 61400-12-2:2013
61400-12-2 © IEC:2013 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

WIND TURBINES –

Part 12-2: Power performance of electricity-producing
wind turbines based on nacelle anemometry

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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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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6) All users should ensure that they have the latest edition of this publication.
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) 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 61400-12-2 has been prepared by IEC technical committee 88:
Wind turbines.
The text of this standard is based on the following documents:
FDIS Report on voting
88/442/FDIS 88/445/RVD

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.

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SIST EN 61400-12-2:2013
– 6 – 61400-12-2 © IEC:2013
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.


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 61400-12-2:2013
61400-12-2 © IEC:2013 – 7 –
INTRODUCTION
The purpose of this part of IEC 61400-12 is to provide a uniform methodology of
measurement, analysis, and reporting of power performance characteristics for individual
electricity-producing wind turbines utilising nacelle-anemometry methods. This standard is
intended to be applied only to horizontal axis wind turbines of sufficient size that the nacelle-
mounted anemometer does not significantly affect the flow through the turbine’s rotor and
around the nacelle and hence does not affect the wind turbine’s performance. The intent of
this standard is that the methods presented herein be utilised when the requirements set forth
in IEC 61400-12-1:2005 are not feasible. This will ensure that the results are as consistent,
accurate, and reproducible as possible within the current state of the art for instrumentation
and measurement techniques.
This procedure describes how to characterise a wind turbine’s power performance
characteristics in terms of a measured power curve and the estimated annual energy
production (AEP) based on nacelle-anemometry. In this procedure, the anemometer is located
on or near the test turbine’s nacelle. In this location, the anemometer is measuring wind
speed that is strongly affected by the test turbine’s rotor. This procedure includes methods for
determining and applying appropriate corrections for this interference. However, it must be
noted that these corrections inherently increase the measurement uncertainty compared to a
properly-configured test conducted in accordance with IEC 61400-12-1:2005. The procedure
also provides guidance on determination of measurement uncertainty including assessment of
uncertainty sources and recommendations for combining them into uncertainties in reported
power and AEP.
A key element of power performance testing is the measurement of wind speed. Even when
anemometers are carefully calibrated in a quality wind tunnel, fluctuations in magnitude and
direction of the wind vector can cause different anemometers to perform differently in the
field. Further, the flow conditions close to a turbine nacelle are complex and variable.
Therefore special care should be taken in the selection and installation of the anemometer.
These issues are addressed in this standard.
The standard will benefit those parties involved in the manufacture, installation, planning and
permitting, operation, utilisation and regulation of wind turbines. When appropriate, the
technically accurate measurement and analysis techniques recommended in this standard
should be applied by all parties to ensure that continuing development and operation of wind
turbines is carried out in an atmosphere of consistent and accurate communication relative to
environmental concerns. This standard presents measurement and reporting procedures
expected to provide accurate results that can be replicated by others.
Meanwhile, a user of the standard should be aware of differences that arise from large
variations in wind shear and turbulence intensity, and from the chosen criteria for data
selection. Therefore, a user should consider the influence of these differences and the data
selection criteria in relation to the purpose of the test before contracting power performance
measurements.

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SIST EN 61400-12-2:2013
– 8 – 61400-12-2 © IEC:2013
WIND TURBINES –

Part 12-2: Power performance of electricity-producing
wind turbines based on nacelle anemometry



1 Scope
This part of IEC 61400-12 specifies a procedure for verifying the power performance
characteristics of a single electricity-producing, horizontal axis wind turbine, which is not
considered to be a small wind turbine per IEC 61400-2. It is expected that this standard will
be used when the specific operational or contractual specifications may not comply with the
requirements set forth in IEC 61400-12-1:2005. The procedure can be used for power
performance evaluation of specific turbines at specific locations, but equally the methodology
can be used to make generic comparisons between different turbine models or different
turbine settings.
The wind turbine power performance characterised by the measured power curve and the
estimated AEP based on nacelle-measured wind speed will be affected by the turbine rotor
(i.e. speeded up or slowed down wind speed). The nacelle-measured wind speed shall be
corrected for this flow distortion effect. Procedures for determining that correction will be
included in the methodology. In IEC 61400-12-1:2005, an anemometer is located on a
meteorological tower that is located between two and four rotor diameters upwind of the test
turbine. This location allows direct measurement of the ‘free’ wind with minimum interference
from the test turbine’s rotor. In this IEC 61400-12-2 procedure, the anemometer is located on
or near the test turbine’s nacelle. In this location, the anemometer is measuring wind speed
that is strongly affected by the test turbine’s rotor and the nacelle. This procedure includes
methods for determining and applying appropriate corrections for this interference. However,
it should be noted that these corrections inherently increase the measurement uncertainty
compared to a properly-configured test conducted in accordance with IEC 61400-12-1:2005.
This IEC 61400-12-2 standard describes how to characterise a wind turbine’s power
performance in terms of a measured power curve and the estimated AEP. The measured
power curve is determined by collecting simultaneous measurements of nacelle-measured
wind speed and power output for a period that is long enough to establish a statistically
significant database over a range of wind speeds and und
...