IEC 61400-12-1:2005

IEC 61400-12-1
Edition 1.0 2005-12
INTERNATIONAL
STANDARD
Wind turbines –
Part 12-1: Power performance measurements of electricity producing wind
turbines
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IEC 61400-12-1
Edition 1.0 2005-12
INTERNATIONAL
STANDARD
Wind turbines –
Part 12-1: Power performance measurements of electricity producing wind
turbines
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XC
ICS 27.180 ISBN 2-8318-8333-4
– 2 – 61400-12-1  IEC:2005(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.8
2 Normative references .8
3 Terms and definitions .9
4 Symbols and units .11
5 Preparation for performance test .14
5.1 Wind turbine and electrical connection .14
5.2 Test site .14
6 Test equipment.16
6.1 Electric power .16
6.2 Wind speed .16
6.3 Wind direction .17
6.4 Air density.17
6.5 Rotational speed and pitch angle.17
6.6 Blade condition .17
6.7 Wind turbine control system .17
6.8 Data acquisition system.18
7 Measurement procedure.18
7.1 General .18
7.2 Wind turbine operation .18
7.3 Data collection .18
7.4 Data rejection.19
7.5 Data correction.19
7.6 Database.19
8 Derived results .20
8.1 Data normalization .20
8.2 Determination of the measured power curve.21
8.3 Annual energy production (AEP) .21
8.4 Power coefficient.22
9 Reporting format.23

Annex A (normative) Assessment of obstacles at the test site.33
Annex B (normative) Assessment of terrain at the test site .36
Annex C (normative) Site calibration procedure .37
Annex D (normative) Evaluation of uncertainty in measurement.39
Annex E (informative) Theoretical basis for determining the uncertainty of
measurement using the method of bins.41
Annex G (normative) Mounting of instruments on the meteorological mast.66
Annex H (normative) Power performance testing of small wind turbines.74
Annex I (normative) Classification of anemometry.77
Annex J (informative) Assessment of cup anemometry .79
Annex K (informative) In situ comparison of anemometers .88

Bibliography.90

61400-12-1  IEC:2005(E) – 3 –

Figure 1 – Requirements as to distance of the meteorological mast and maximum
allowed measurement sectors.15
Figure 2 – Presentation of example database A and B: power performance test scatter
plots sampled at 1 Hz (mean values averaged over 10 min).26
Figure 3 – Presentation of example measured power curve for databases A and B .27
Figure 4 – Presentation of example C curve for databases A and B.28
p
Figure 5 – Presentation of example site calibration (only the sectors 20° to 30°, 40° to
60°, 160° to 210° and 330° to 350° are valid sectors).29
Figure A.1 – Sectors to exclude due to wakes of neighbouring and operating wind
turbines and significant obstacles .34
Figure A.2 – An example of sectors to exclude due to wakes of the wind turbine under
test, a neighbouring and operating wind turbine and a significant obstacle.35
Figure B.1 – Illustration of area to be assessed, top view.36
Figure G.1 – Example of a top-mounted anemometer and requirements for mounting .66
Figure G.2 – Example of alternative top-mounted primary and control anemometers
positioned side-by-side and wind vane and other instruments on the boom.67
Figure G.3 – Example of a top-mounted anemometer and mounting of control
anemometer, wind vane and other sensors on a boom.68
Figure G.4 – Example of top-mounted primary and control anemometers positioned
side-by-side, wind vane and other instruments on the boom .69
Figure G.5 – Iso-speed plot of local flow speed around a cylindrical mast, normalised
by free-field wind speed (from the left); analysis by 2 dimensional Navier-Stokes
computations .70
Figure G.6 – Centre-line relative wind speed as a function of distance R from the
centre of a tubular mast and mast diameter d .70
Figure G.7 – Representation of a three-legged lattice mast showing the centre-line
wind speed deficit, the actuator disc representation of the mast with the leg distance L
and distance R from the centre of the mast to the point of observation.71
Figure G.8 – Iso-speed plot of local flow speed around a triangular lattice mast with a
C of 0,5 normalised by free-field wind speed (from the left); analysis by 2
T
dimensional Navier-Stokes computation and actuator disc theory .72
Figure G.9 – Centre-line relative wind speed as a function of distance R from the
centre of a triangular lattice mast of face width L for various C values.72
T
Figure J.1 – Measured angular response of a cup anemometer compared to cosine
response.79
Figure J.2 – Wind tunnel torque measurements on a cup anemometer at 8 m/s .80
Figure J.3 – Example of bearing friction torque measurements .81
Figure J.4 – Distribution of vertical wind speed components assuming a fixed ratio
between horizontal and vertical standard deviation in wind speed.82
Figure J.5 – Calculation of the total deviation with respect to the cosine response.83
Figure J.6 – Probability distributions for three different average angles of inflow.84
Figure J.7 – Total deviation from cosine response for three different average angles of
inflow over horizontal turbulence intensity.84
Figure J.8 – Example of an anemometer that does not fulfil the slope criterion .85
Figure J.9 – Example of deviations of a Class 2.0A cup anemometer.87

– 4 – 61400-12-1  IEC:2005(E)

Table 1 – Example of presentation of a measured power curve for database A .30
Table 2 – Example of presentation of a measured power curve for database B .31
Table 3 – Example of presentation of estimated annual energy production (database A).32
Table 4 – Example of presentation of estimated annual energy production (database B).32
Table B.1 – Test site requirements: topographical variations .36
Table D.1 – List of uncertainty components .40
Table E.1 – Expanded uncertainties.43
Table E.2 – List of categories B and A uncertainties .45
Table E.3 – Uncertainties from site calibration .53
Table E.4 – Sensitivity factors (database A).54
Table E.5 – Sensitivity factors (database B).55
Table E.6 – Category B uncertainties (database A) .56
Table E.7 – Category B uncertainties (database B) .57
Table F.1 – Example of evaluation of anemometer calibration uncertainty.62
Table G.1 – Estimation method for C for various types of lattice tower.73
T
Table H.1 – Battery bank voltage settings .76
Table I.1 – Influence parameter ranges (based on 10 min averages) of Classes A and B.78

61400-12-1  IEC:2005(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND TURBINES –
Part 12-1: Power performance measurements
of electricity producing wind turbines

FOREWORD
1) The International Electrotechnical Commission (IEC) is a w
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