IEC 61400-12-1: Performance Measurements of Wind Turbines

Wind turbines in line under sky and assured to the power performance measurements of IEC 61400-12-1 Ed. 3.0 B:2022.

By mid-2022, in the United States alone, the installed wind capacity totaled 139,145 megawatts. But wind power accomplishments are found throughout the globe. The tallest wind turbine in the world is located offshore in Denmark, and it stands 199 meters tall with a capacity of 7.2 MW.

The performance of wind turbines, regardless of their size, is influenced by several factors. According to IEC 61400-12-1 Ed. 3.0 b:2022 – Wind energy generation systems – Part 12-1: Power performance measurements of electricity producing wind turbines, wind turbine power performance characteristics are determined by the measured power curve (the relationship between the wind speed and the wind turbine power output) and the estimated annual energy production (AEP).

What Is Measured Power Curve?

The measured power curve, as addressed in the IEC 61400-12-1 Ed. 3.0 b:2022 standard, is determined by collecting measurements of meteorological variables and wind turbine signals simultaneously. These two characteristics together are the primary determinants of a wind turbine’s performance, and, by collecting data for a long enough period, users of the standard can establish a statistically significant database over a range of wind speeds and under varying wind and atmospheric conditions.

Meteorological variables touched upon in IEC 61400-12-1 Ed. 3.0 b:2022 include wind shear, wind veer, wind speed, air density, and turbulence. The power curve, as per the standard, is climate-specific, and it abides by certain rules. For example, “the wind speed at a point in space is defined as the horizontal wind speed.”

Wind turbine signals include the power output of the rotor, and other turbine-specific considerations that are to be determined for the measured power curve.

What Is Annual Energy Production (AEP)?

The AEP is calculated by applying the measured power curve to reference wind speed frequency distributions. In adherence to IEC 61400-12-1 Ed. 3.0 b:2022, AEP should be calculated in two ways, one designated “AEP-measured,” and the other “AEP-extrapolated.” This value serves as an estimate of the total energy of a wind turbine throughout a one-year period.

What Is IEC 61400-12-1 Ed. 3.0 b:2022?

The methods for determining the measured power curve and annual energy production, along with supplementary information and formulas for calculating the necessary values, are detailed in IEC 61400-12-1 Ed. 3.0 b:2022. The procedure covered in the document can be used for performance evaluation of specific wind turbines at specific locations, but it also can be used to make generic comparisons between different wind turbine models or different wind turbine settings when site-specific conditions and similar influences are considered. This methodology should be assisted by uncertainty sources and their effects.

The IEC 61400-12-1 Ed. 3.0 b:2022 standard applies to the testing of wind turbines of all types and sizes connected to the electrical power network, but it can also be used to determine the power performance characteristics of small wind turbines when connected to either the electric power network or a battery bank.

Anticipated users of IEC 61400-12-1 Ed. 3.0 b:2022 include wind turbine manufacturers, purchasers, operators, and planners or regulators.

Changes to IEC 61400-12-1 Ed. 3.0 b:2022

IEC 61400-12-1 Ed. 3.0 b:2022 updates and supersedes the second edition of the standard, which was published in 2017. This revision incorporates corrections from IEC 61400-12-1:2017/Cor.1:2019, IEC 61400-12-1:2017/Cor.2:2020 and IEC 61400-12-1:2017/Cor.3:2021.

Specifically, technical corrections have been applied to Equations (E.8), (E.44) and (E.17). A further technical correction to Equation (E.45) has been made to correct inconsistent units in the components of the summation.

IEC 61400-12-1 Ed. 3.0 b:2022 – Wind energy generation systems – Part 12-1: Power performance measurements of electricity producing wind turbines is available on the ANSI Webstore. Anyone in need of it and the other wind turbine standards in the IEC 61400-12 series might be interested in the IEC 61400 – Wind Turbines Package.

Changes to IEC 61400-12-1 Ed. 2.0 b:2017

The second edition of this standard was a significant revision, updating the first edition of the document that was published in 2005. This revision included the following significant technical changes:

  • new definition of wind speed
  • inclusion of wind shear and wind veer
  • revision of air density correction
  • revision of site calibration
  • revision to definition of power curve
  • interpolation to bin centre method
  • revision of obstacle model
  • clarification of topography requirements
  • new annex on mast induced flow distortion
  • revision to anemometer classifications
  • inclusion of ultrasonic anemometers
  • cold climate annex added
  • database A changed to special database
  • revision of uncertainty annex
  • inclusion of remote sensing
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