Wind energy generation systems - Part 12-3: Power performance - Measurement based site calibration

IEC 61400-12-3:2022 specifies a measurement and analysis procedure for deriving the wind speed correction due to terrain effects and applies to the performance testing of wind turbines of all types and sizes connected to the electrical power network as described in IEC 61400‑12‑1. The procedure applies to the performance evaluation of specific wind turbines at specific locations. The purpose of this part of IEC 61400 is to provide a uniform methodology that will ensure consistency, accuracy and reproducibility in the measurement and analysis of a site calibration for use in the determination of the power performance of wind turbines. This document provides guidance in the measurement, analysis, and reporting of the site calibration for subsequent use in power performance testing for wind turbines.
This first edition of IEC 61400-12-3 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 12-3: Performance de puissance - Étalonnage du site fondé sur le mesurage

IEC 61400-12-3:2022 spécifie une procédure de mesure et d’analyse de dérivation de la correction de vitesse du vent en raison des effets de terrain, et s’applique aux essais de performance d’éoliennes raccordés au réseau électrique de tous types et de toutes tailles, comme cela est décrit dans l’IEC 61400-12-1. La procédure est applicable pour l’évaluation de la performance d'éoliennes spécifiques sur des sites spécifiques. La présente partie de l'IEC 61400 a pour objet de fournir une méthodologie uniforme qui garantit la cohérence, l’exactitude et la reproductibilité du mesurage et de l'analyse d’un étalonnage de site pour utilisation, afin de déterminer la performance de puissance des éoliennes. Le présent document fournit des recommandations relatives au mesurage, à l'analyse et à la consignation des rapports de l’étalonnage du site pour une utilisation ultérieure, dans les essais de performance de puissance des éoliennes.
La présente première édition de l’IEC 61400-12-3 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
28-Aug-2022
Current Stage
PPUB - Publication issued
Completion Date
29-Aug-2022
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IEC 61400-12-3
Edition 1.0 2022-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 12-3: Power performance – Measurement based site calibration
Systèmes de génération d'énergie éolienne –
Partie 12-3: Performance de puissance – Étalonnage du site fondé sur le
mesurage
IEC 61400-12-3:2022-08(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61400-12-3
Edition 1.0 2022-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 12-3: Power performance – Measurement based site calibration
Systèmes de génération d'énergie éolienne –
Partie 12-3: Performance de puissance – Étalonnage du site fondé sur le
mesurage
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-5596-4

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---------------------- Page: 3 ----------------------
– 2 – IEC 61400-12-3:2022 © IEC 2022
CONTENTS

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

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

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

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

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

4 Symbols, units and abbreviated terms ........................................................................... 10

5 General ......................................................................................................................... 12

6 Overview of the procedure ............................................................................................. 13

7 Test set-up .................................................................................................................... 14

7.1 Considerations for selection of the test wind turbine and location of the

meteorological mast .............................................................................................. 14

7.1.1 General ......................................................................................................... 14

7.1.2 Type A: .......................................................................................................... 14

7.1.3 Type B: .......................................................................................................... 14

7.1.4 Type C:.......................................................................................................... 15

7.2 Instrumentation ..................................................................................................... 15

8 Data acquisition and rejection criteria ............................................................................ 16

9 Analysis ......................................................................................................................... 17

9.1 General ................................................................................................................. 17

9.2 Assessment of site shear conditions ..................................................................... 17

9.2.1 Shear calculations and characterisation plots ................................................ 17

9.2.2 Assess significance of shear .......................................................................... 17

9.2.3 Establish correlation of shear between locations ............................................ 18

9.3 Method 1: Bins of wind direction and wind shear ................................................... 19

9.4 Method 2: Linear regression method where wind shear is not a significant

influence ............................................................................................................... 19

9.5 Additional calculations .......................................................................................... 20

10 Site calibration uncertainty ............................................................................................ 21

10.1 Site calibration category A uncertainty .................................................................. 21

10.1.1 Site calibration K-fold analysis ....................................................................... 21

10.1.2 Site calibration statistical uncertainty for each fold......................................... 22

10.2 Site calibration category B uncertainty .................................................................. 23

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

10.2.2 Anemometer – Pre-calibration ....................................................................... 23

10.2.3 Anemometer – Post-calibration ...................................................................... 23

10.2.4 Anemometer – Classification ......................................................................... 23

10.2.5 Anemometer – Mounting ................................................................................ 24

10.2.6 Anemometer – Data acquisition ..................................................................... 24

10.2.7 Anemometer – Lightning finial........................................................................ 25

10.3 Combining uncertainties in the wind speed measurement from flow distortion

due to site calibration u ................................................................................... 25

VT,i

10.4 Combined uncertainty ........................................................................................... 26

11 Quality checks and additional uncertainties ................................................................... 26

11.1 Convergence check .............................................................................................. 26

11.2 Correlation check for linear regression (see 9.4) ................................................... 26

11.3 Change in correction between adjacent wind direction bins ................................... 26

---------------------- Page: 4 ----------------------
IEC 61400-12-3:2022 © IEC 2022 – 3 –

11.3.1 General ......................................................................................................... 26

11.3.2 Removal of the wind direction sensor between site calibration and

power performance test ................................................................................. 27

11.4 Site calibration and power performance measurements in different seasons ......... 28

Annex A (informative) Verification of results ......................................................................... 29

Annex B (informative) Site calibration examples .................................................................. 31

B.1 Example A ............................................................................................................ 31

B.1.1 Site description: ............................................................................................. 31

B.1.2 Site calibration setup: .................................................................................... 31

B.1.3 Site calibration evaluation: ............................................................................. 31

B.1.4 Step 1: Check the significance of wind shear at the site according to

9.2.2: ............................................................................................................. 31

B.1.5 Step 2: Verify correlation of wind shear at wind turbine and reference

meteorological mast locations – Example A ................................................... 32

B.1.6 Step 3: Calculate results according to 9.2.3 ................................................... 33

B.1.7 Step 4: Quality checks and additional uncertainties ....................................... 33

B.2 Example B ............................................................................................................ 35

B.2.1 Site description: ............................................................................................. 35

B.2.2 Site calibration setup: .................................................................................... 35

B.2.3 Step 1: Check the significance of wind shear at the site:............................... 36

B.2.4 Step 2A: Verify correlation of wind shear at wind turbine and reference

meteorological mast locations, example B ..................................................... 36

B.2.5 Step 2B: Attempt to remove non-correlating wind shear data ......................... 38

B.2.6 Step 3: Calculate results ................................................................................ 39

B.2.7 Step 4: Additional uncertainties: .................................................................... 39

B.3 Example C ............................................................................................................ 41

B.3.1 Site description: ............................................................................................. 41

B.3.2 Site calibration setup: .................................................................................... 41

B.3.3 Step 1: Check the significance of wind shear at the site:............................... 42

B.3.4 Step 2: Verify correlation of wind shear at wind turbine and reference

meteorological mast locations, example C ..................................................... 42

B.3.5 Step 3: Calculate results ................................................................................ 42

B.3.6 Step 4: Quality checks and uncertainty ......................................................... 42

B.3.7 Anemometer operational uncertainty: ............................................................. 42

B.3.8 Convergence check: ...................................................................................... 42

B.3.9 Change in magnitude of correction between bins: .......................................... 43

B.3.10 Wind vane adjustment: .................................................................................. 43

B.3.11 Seasonal uncertainty adjustment: .................................................................. 43

Bibliography .......................................................................................................................... 44

Figure 1 – Site calibration flow chart ..................................................................................... 13

Figure 2 – Terrain types ........................................................................................................ 15

Figure A.1 – Example of the results of a verification test ....................................................... 30

Figure B.1 – Wind shear exponent vs. time of day, Example A .............................................. 32

Figure B.2 – Wind shear exponents at wind turbine location vs. reference

meteorological mast, example A where the colour axis = wind speed (m/s) ........................... 32

Figure B.3 – Wind speed ratios and number of data points vs. wind shear exponent

and wind direction bin – wind speed ratios (full lines), number of data points (dotted

lines) .................................................................................................................................... 33

---------------------- Page: 5 ----------------------
– 4 – IEC 61400-12-3:2022 © IEC 2022

Figure B.4 – Data convergence check for 190° bin ................................................................ 35

Figure B.5 – Wind shear exponent vs. time of day, example B .............................................. 36

Figure B.6 – Wind shear exponents at wind turbine location vs. reference

meteorological mast, example B ........................................................................................... 36

Figure B.7 – Linear regression of wind turbine location vs. reference meteorological

mast hub height wind speeds for 330° bin ............................................................................. 37

Figure B.8 – Wind speed ratios vs. wind speed for the 330° bin ............................................ 37

Figure B.9 – Wind speed ratios vs. wind shear for the 330° bin ............................................. 38

Figure B.10 – Wind shear exponents at wind turbine location vs. reference

meteorological mast post-filtering ......................................................................................... 38

Figure B.11 – Linear regression of wind turbine location vs. reference meteorological

mast hub height wind speeds for 330° bin, post-filtering ........................................................ 39

Figure B.12 – Wind speed ratios vs. wind speed for the 330° bin, post-filtering ..................... 39

Figure B.13 – Data convergence check for 330° bin .............................................................. 40

Figure B.14 – Site calibration wind shear vs. power curve test wind shear ............................ 41

Figure B.15 – Convergence check for 270° bin ..................................................................... 43

Table B.1 – Site calibration flow corrections (wind speed ratio) ............................................. 34

Table B.2 – Site calibration data count .................................................................................. 34

Table B.3 – r values for each wind direction bin .................................................................. 40

Table B.4 – Additional uncertainty due to change in bins for example B ................................ 40

Table B.5 – Additional uncertainty due to change in bins for example C ................................ 43

---------------------- Page: 6 ----------------------
IEC 61400-12-3:2022 © IEC 2022 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –
Part 12-3: Power performance –
Measurement based site calibration
FOREWORD

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

IEC 61400-12-3 has been prepared by IEC technical committee 88: Wind energy generation

systems. It is an International Standard.

This first edition of IEC 61400-12-3 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.
---------------------- Page: 7 ----------------------
– 6 – IEC 61400-12-3:2022 © IEC 2022
The text of this International Standard is based on the following documents:
Draft Report on voting
88/824/CDV 88/869/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 publication indicates that it

contains colours which are considered to be useful for the correct understanding of its

contents. Users should therefore print this document using a colour printer.
---------------------- Page: 8 ----------------------
IEC 61400-12-3:2022 © IEC 2022 – 7 –
INTRODUCTION

The purpose of this part of IEC 61400 is to provide a uniform methodology that will ensure

consistency, accuracy and reproducibility in the measurement and analysis of a site calibration

for use in the determination of the power performance of wind turbines. This document has

been prepared with the anticipation that it would be applied by:

a) a wind turbine manufacturer striving to meet well-defined power performance requirements

and/or a possible declaration system;
b) a wind turbine purchaser in specifying such performance requirements;

c) a wind turbine operator who may be required to verify that stated, or required, power

performance specifications are met for new or refurbished units;

d) a wind turbine planner or regulator who will need to be able to accurately and fairly define

power performance characteristics of wind turbines in response to regulations or permit

requirements for new or modified installations.

This document provides guidance in the measurement, analysis, and reporting of the site

calibration for subsequent use in power performance testing for wind turbines. This document

will benefit those parties involved in the manufacture, installation planning and permitting,

operation, utilization, and regulation of wind turbines. The technically accurate measurement

and analysis techniques recommended in this document 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 wind turbine performance.

This document presents measurement and reporting procedures expected to provide accurate

results that can be replicated by others. Meanwhile, a user of this document should be aware

of differences that arise from large variations in wind shear and turbulence. 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 the power performance measurements.

The committee recognizes that the restructuring of the IEC 61400-12 series represents a

significant increase in complexity and perhaps greater difficulty to implement. However, it

represents the committee’s best attempt to address issues introduced by larger wind turbines

operating in significant wind shear and complex terrain. The committee recommends that the

new techniques introduced be validated immediately by test laboratories through inter-lab

proficiency testing. The committee recommends a Maintenance Cycle Report be written within

three years of the publication of this document which includes recommendations, clarifications

and simplifications that will improve the practical implementation of this document. If necessary

a revision should be proposed at the same time to incorporate these recommendations,

clarifications and simplifications.
---------------------- Page: 9 ----------------------
– 8 – IEC 61400-12-3:2022 © IEC 2022
WIND ENERGY GENERATION SYSTEMS –
Part 12-3: Power performance –
Measurement based site calibration
1 Scope

This part of IEC 61400 specifies a measurement and analysis procedure for deriving the wind

speed correction due to terrain effects and applies to the performance testing of wind turbines

of all types and sizes connected to the electrical power network as described in IEC 61400-12-1.

The procedure applies to the performance evaluation of specific wind turbines at specific

locations.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any

amendments) applies.
IEC 61400-12-1, Wind energy generation systems – Part 12-1: Power performance
measurements of electricity producing wind turbines
IEC 61400-12-5, Wind energy generation systems – Part 12-5: Power performance –
Assessment of obstacles and terrain
IEC 61400-50-1, Wind energy generation systems – Part 50-1: Wind measurement –
Application of meteorological mast, nacelle and spinner mounted instruments

ISO/IEC GUIDE 98-3:2008, Uncertainty of measurement – Part 3: Guide to the expression of

uncertainty in measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological da
...

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