IEC 61400 is a class of IEC international standards regarding wind turbines.
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The 61400 is a set of design requirements made to ensure that wind turbines are appropriately engineered against damage from hazards within the planned lifetime. The standard concerns most aspects of the turbine life from site conditions before construction, to turbine components being tested,[1] assembled and operated.[2]
Wind turbines are capital intensive, and are usually purchased before they are being erected and commissioned.
Some of these standards provide technical conditions verifiable by an independent, third party, and as such are necessary in order to make business agreements so wind turbines can be financed and erected.[1][3]
IEC started standardizing international certification on the subject in 1995, and the first standard appeared in 2001.[1]
The common set of standards sometimes replace the various national standards, forming a basis for global certification.[1]
In the U.S., standards are intended to be compatible with IEC standards,[4] and some parts of 61400 are required documentation.[5]
The U.S. National Renewable Energy Laboratory participates in IEC standards development work,[6] and tests equipment according the these standards.[7]
In Canada, the previous national standards were outdated and impeded the wind industry, and they were updated and harmonized with 61400 by the Canadian Standards Association with several modifications.[8]
Wind turbines are designed for specific conditions. During the construction and design phase assumptions are made about the wind climate that the wind turbines will be exposed to. 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. Turbine classes are determined by three parameters the average wind speed, extreme 50-year gust, and turbulence.[9]
Turbulence intensity quantifies how much the wind varies typically within 10 minutes. Because the fatigue loads of a number of major components in a wind turbine are mainly caused by turbulence, the knowledge of how turbulent a site is of crucial importance. Normally the wind speed increases with increasing height. In flat terrain the wind speed increases logarithmically with height. In complex terrain the wind profile is not a simple increase and additionally a separation of the flow might occur, leading to heavily increased turbulence.[10]
| Wind Class/Turbulence | Annual average wind speed at hub-height
(m/s) |
Extreme 50-year gust in meters/second (miles/hour) |
|---|---|---|
| Ia High wind - Higher Turbulence 18% | 10.0 | 70 (156) |
| Ib High wind - Lower Turbulence 16% | 10.0 | 70 (156) |
| IIa Medium wind - Higher Turbulence 18% | 8.5 | 59.5 (133) |
| IIb Medium wind - Lower Turbulence 16% | 8.5 | 59.5 (133) |
| IIIa Low wind - Higher Turbulence 18% | 7.5 | 52.5 (117) |
| IIIb Low wind - Lower Turbulence 16% | 7.5 | 52.5 (117) |
| IV | 6.0 | 42.0 (94) |
The extreme wind speeds are based on the 3 second average wind speed. Turbulence is measured at 15 m/s wind speed.
List compiled from a number of sources.[2][15][16]