Wind turbine classes
Turbine wind class is just one of the factors which need to consider during the complex process of planning a wind power plant. Wind classes determine which turbine is suitable for the normal wind conditions of a particular site. They’re mainly defined by the average annual wind speed (measured at the turbine’s hub height), the speed of extreme gusts that could occur over 50 years, and how much turbulence there is at the wind site.
The three wind classes for wind turbines are defined by an International Electrotechnical Commission standard (IEC), and correspond to high, medium and low wind as follows:
| Turbine Class | IEC I High Wind | IEC II Medium Wind | IEC III Low Wind |
|---|---|---|---|
| Annual average wind speed | 10 m/s | 8.5 m/s | 7.5 m/s |
| Extreme 50-year gust | 70 m/s | 59.5 m/s | 52.5 m/s |
| Turbulence classes | A 18% | A 18% | A 18% |
| B 16% | B 16% | B 16% |
