IEC 61400-12-2:2022

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

IEC 61400-12-2:2022 specifies a procedure for verifying the power performance characteristics of a single electricity-producing, horizontal axis wind turbine that is not considered to be a small wind turbine per IEC 61400-2. It is expected that this document be used when the specific operational or contractual specifications do not comply with the requirements set out in IEC 61400-12-1. The purpose of this document 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 document 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. This second edition of IEC 61400-12-2 is part of a structural revision that cancels and replaces the performance standards IEC 61400-12-1:2017 and IEC 61400-12-2:2013. The structural revision contains no technical changes with respect to IEC 61400-12-1:2017 and IEC 61400‑12‑2:2013, but the parts that relate to wind measurements, measurement of site calibration and assessment of obstacle and terrain have been extracted into separate standards.

Systèmes de génération d'énergie éolienne - Partie 12-2: Performance de puissance des éoliennes de production d'électricité fondée sur l'anémométrie de nacelle

L'IEC 61400-12-2:2022 spécifie une procédure de vérification des caractéristiques de performance de puissance d'une éolienne simple de production d'électricité à axe horizontal, qui n'est pas considérée comme un petit aérogénérateur selon l’IEC 61400-2. Il est prévu que le présent document soit utilisé lorsque les spécifications de fonctionnement ou contractuelles spécifiques ne sont pas conformes aux exigences définies dans l’IEC 61400‑12‑1. Le présent document a pour objet de fournir une méthodologie uniforme de mesure, d'analyse et de rapport des caractéristiques de performance de puissance de chacune des éoliennes de production d'électricité qui applique les méthodes d'anémométrie de nacelle. Le présent document est destiné à être appliqué uniquement aux éoliennes à axe horizontal et de taille suffisante pour que l’anémomètre monté sur la nacelle n’ait pas d’influence significative sur l’écoulement d’air dans le rotor de l’éolienne et autour de la nacelle, et n’ait donc pas d’influence sur les performances de l’éolienne. Cette deuxième édition de l’IEC 61400-12-2 fait partie d’une révision structurelle qui annule et remplace les normes de performance IEC 61400-12-1:2017 et IEC 61400-12-2:2013. Cette révision structurelle ne contient aucune modification technique par rapport à l'IEC 61400‑12‑1:2017 et l'IEC 61400-12‑2:2013. Toutefois, les parties relatives aux mesurages du vent, au mesurage de l'étalonnage du site et à l'évaluation des obstacles et du terrain ont été extraites vers des normes distinctes.

General Information

• Status: Published
• Publication Date: 04-Sep-2022
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: TC 88 - Wind energy generation systems
• Drafting Committee: MT 12-1 - TC 88/MT 12-1
• Current Stage: PPUB - Publication issued
• Start Date: 26-Sep-2022
• Completion Date: 05-Sep-2022

Relations

• Replaces: IEC 61400-12-1:2017 - Wind energy generation systems - Part 12-1: Power performance measurements of electricity producing wind turbines
• Effective Date: 05-Sep-2023
• Revises: IEC 61400-12-2:2013 - Wind turbines - Part 12-2: Power performance of electricity-producing wind turbines based on nacelle anemometry
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61400-12-2
®

Edition 2.0 2022-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Wind energy generation systems –
Part 12-2: Power performance of electricity producing wind turbines based on
nacelle anemometry

Systèmes de génération d'énergie éolienne –
Partie 12-2: Performance de puissance des éoliennes de production d'électricité
fondée sur l'anémométrie de nacelle

IEC 61400-12-2:2022-09(en-fr)

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IEC 61400-12-2

®


Edition 2.0 2022-09




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Wind energy generation systems –

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

nacelle anemometry




Systèmes de génération d'énergie éolienne –

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


fondée sur l'anémométrie de nacelle













INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 27.180 ISBN 978-2-8322-5594-0




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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– 2 – IEC 61400-12-2:2022 © IEC 2022
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 Symbols, units and abbreviated terms . 14
5 Overview of test method . 17
6 Preparation for performance test . 19
6.1 General . 19
6.2 Wind turbine . 19
6.3 Test site . 19
6.4 Nacelle wind speed transfer function . 20
6.5 Test plan . 20
7 Test equipment . 20
7.1 Electric power . 20
7.2 Wind speed . 21
7.3 Wind direction . 21
7.4 Air density. 21
7.5 Rotor speed . 22
7.6 Pitch angle . 22
7.7 Wind turbine status . 22
7.8 Data acquisition . 22
8 Measurement procedure . 23
8.1 General . 23
8.2 Wind turbine operation . 23
8.3 Data system(s) synchronisation . 23
8.4 Data collection . 24
8.5 Data quality check . 24
8.5.1 General . 24
8.5.2 Measured signals are in range and available . 24
8.5.3 Sensors are operating properly . 24
8.5.4 Ensure data acquisition system(s) is/are operating properly. 25
8.5.5 Sector self-consistency check . 25
8.6 Data rejection . 25
8.7 Data correction . 26
8.8 Database . 26
9 Derived results . 27
9.1 Data normalisation – Density correction . 27
9.2 Determination of measured power curve . 28
9.3 Annual energy production (AEP) . 28
9.4 Power coefficient . 29
9.5 Uncertainty analysis . 30
10 Reporting format . 30
Annex A (normative) Nacelle wind speed transfer function validity procedure . 38
A.1 General . 38

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IEC 61400-12-2:2022 © IEC 2022 – 3 –
A.2 Measurement procedure: . 38
A.3 Terrain class and slope: . 38
A.4 Measurement hardware: . 38
A.5 Other turbine hardware: . 38
A.6 Turbine controls: . 39
Annex B (normative) Evaluation of uncertainty in measurement . 40
B.1 General . 40
B.2 The measurands . 40
B.3 Uncertainty components. 40
B.4 Wind direction uncertainty . 42
Annex C (normative) Theoretical basis for determining the uncertainty of
measurement using the method of bins . 43
C.1 General . 43
C.2 Propagation of uncertainty through the stages of NTF/NPC measurement . 44
C.3 Category A uncertainties . 47
C.3.1 General . 47
C.3.2 Category A uncertainty in electric power . 47
C.4 Category B uncertainties . 49
C.4.1 General . 49
C.4.2 Category B uncertainties in climatic variations . 49
C.5 Expanded uncertainty . 49
Annex D (normative) NPC uncertainty estimates and calculation . 51
D.1 Methods and assumptions. 51
D.1.1 General . 51
D.1.2 Nacelle power curve uncertainty component estimates . 51
D.1.3 Wind direction uncertainty . 54
D.1.4 Contribution factors . 55
D.2 Uncertainty example calculations . 57
D.2.1 Example description . 57
D.2.2 Example case – NTF uncertainty . 57
D.2.3 Example case – NPC uncertainty . 58
Annex E (normative) Allowable anemometry instrument types. 60
E.1 General . 60
E.2 Calibration of sonic anemometers . 60
E.2.1 General . 60
E.2.2 Step 1: Wind speed calibration (required) . 60
E.2.3 Step 2: Wind direction calibration (required) . 61
E.2.4 Step 3: Tilting test (recommended) . 61
E.3 Recalibration of sonic anemometers . 61
E.4 Uncertainty of sonic and propeller anemometers . 61
Annex F (informative) Results and uncertainty considerations . 62
F.1 General . 62
F.2 Method for calculation of measurement uncertainty . 62
F.3 Method for calculation of sampling uncertainty . 66
F.4 Combined measurement and sampling uncertainty . 66
Annex G (informative) Example multi-turbine NTF/NPC uncertainty calculation . 67
G.1 Overview. 67
G.2 Outline of procedure: . 67

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– 4 – IEC 61400-12-2:2022 © IEC 2022
G.3 Example of measurement uncertainty calculation . 70
G.4 Example of sampling uncertainty calculation . 74
G.5 Combined uncertainty . 74
G.6 Discussion of sample size and uncertainty . 74
Annex H (informative) Organisation of test, safety and communication . 76
H.1 Overview. 76
H.2 Responsibility for test . 76
H.3 Safety during test . 76
H.4 Communication . 76
H.5 Prior to test . 76
H.6 During test . 76
H.7 After test . 77
Bibliography . 78

Figure 1 – Procedural overview . 18
Figure 2 – Presentation of sample data: nacelle power performance test scatter plots . 34
Figure 3 – Presentation of sample data: binned power curve with uncertainty bands . 34
Figure 4 – Example of sample data: measured power curve and C curve . 35
p
Figure G.1 – Impact of multiple turbine testing on measurement uncertainty . 74
Figure G.2 – Impact of multiple turbine testing on sampling uncertainty . 75

Table 1 – Example of a measured power curve . 36
Table 2 – Example of estimated annual energy production . 37
Table B.1 – Uncertainty components in nacelle power curve evaluation . 41
Table B.2 – Uncertainty components in nacelle based absolute wind direction . 42
Table C.1 – Example cancellation sources . 45
Table C.2 – List of category A and B uncertainties for NPC . 48
Table C.3 – Expanded uncertainties. 50
Table D.1 – Estimates for uncertainty components from NPC measurement . 52
Table D.2 – Estimates for u for NPC terrain class . 54
V5,i
Table D.3 – Estimates for uncertainty components for wind direction . 55
Table D.4 – Estimates for contribution factors for NPC . 56
Table G.1 – List of correlated uncertainty components . 68
Table G.2 – Sample AEP and uncertainty data from three turbines . 70
Table G.3 – Component uncertainty contribution to AEP uncertainty on turbine 1 . 71
Table G.4 – Combination of uncertainty components across turbines . 72

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IEC 61400-12-2:2022 © IEC 2022 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

WIND ENERGY GENERATION SYSTEMS –

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

FOREWORD
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IEC 61400-12-2 has been prepared by IEC technical committee 88: Wind energy generation
systems. It is an International Standard.
This second edition of IEC 61400-12-2 is part of a structural revision that cancels and replaces
the performance standards IEC 61400-12-1:2017 and IEC 61400-12-2:2013. The structural
revision contains no technical changes with respect to IEC 61400-12-1:2017 and
IEC 61400-12-2:2013, but the parts that relate to wind measurements, measurement of site
calibration and assessment of obstacle and terrain have been extracted into separate standards.
The purpose of the re-structure was to allow the future management and revision of the power
performance standards to be carried out more efficiently in terms of time and cost and to provide
a more logical division of the wind measurement requirements into a series of separate
standards which could be referred to by other use case standards in the IEC 61400 series and
subsequently maintained and developed by appropriate experts.

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– 6 – IEC 61400-12-2:2022 © IEC 2022
The text of this International Standard is based on the following documents:
Draft Report on voting
88/823/CDV 88/868/RVC

Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 61400 series, published 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 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 document indicates
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IEC 61400-12-2:2022 © IEC 2022 – 7 –
INTRODUCTION
This second edition contains no technical changes with respect to the previous edition but the
parts that relate to wind measurements, measurement of nacelle transfer functions and
assessment of obstacles and terrain have been extracted into separate standards. The
separated standards comprise:
– IEC 61400-50, Wind measurements – Overview
– IEC 61400-50-1, Wind measurement – Application of meteorological mast, nacelle and
spinner mounted instruments
– IEC 61400-50-2, Wind measurement – Application of ground-mounted remote sensing
technology
– IEC 61400-12, Power performance measurements of electricity producing wind turbines –
Overview
– IEC 61400-12-1, Power performance measurement of electricity producing wind turbines
– IEC 61400-12-2, Power performance of electricity producing turbines based on nacelle
anemometry
– IEC 61400-12-3, Power performance – Measurement based site calibration
– IEC 61400-12-5, Power performance – Assessment of obstacles and terrain
– IEC 61400-12-6, Measurement based nacelle transfer function of electricity producing wind
turbines.
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. The procedure provides guidance on determination
of measurement uncertainty including assessment of uncertainty sources and recommendations
for combining them into uncertainties in reported power and 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 under varying wind and
atmospheric conditions. In order to accurately measure the power curve, the nacelle-measured
wind speed is adjusted using a transfer function to estimate the free stream wind speed. The
procedure to measure such a transfer function is given in IEC 61400-12-6. The AEP is
calculated by applying the measured power curve to the reference wind
...