IEC WIND TURBINES – PART 1: DESIGN REQUIREMENTS. You may have heard that IEC defines wind turbine classes with labels like IIIB, where the roman number refers to a reference wind speed and the index letter. IEC. Second edition. Wind turbine generator systems –. Part 1 : Safety requirements. Aérogénérateurs –. Partie 1: Spécifications de sécurité.
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IEC – Wikipedia
Here, the main principle is that local wind conditions must not exceed those of the models used for turbine classification. Effective turbulence intensity will generally decrease with wind speed due to decreasing stability effects and turbine thrust coefficient.
Wind classes determine which turbine idc suitable for the normal wind conditions of a particular site. Normally the wind speed increases with increasing height. Unlike the NTM turbulence model, site-specific turbulence usually depends on wind direction. Turbine classes are determined by three parameters – the average wind speed, extreme year gust, and turbulence.
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Therefore, the IEC standard applies a representative turbulence intensity for turbine classification, which is defined as a high percentile of the expected natural variation. Views Read Edit View history. Turbine wind class is just one of the factors needing consideration during the complex process of planning a wind power plant. To verify that a wind turbine belongs to a give wind turbine class, it must be proven safe under a set of predefined load cases.
During the construction and design phase assumptions are made about the wind climate that the wind turbines will be exposed to. You may have heard that IEC defines wind turbine classes with labels like III Bwhere the roman number refers to a reference wind speed and the index letter refers to a turbulence category.
IEC started standardizing international certification on the subject inand the first standard appeared in This is the definition in IEC edition 2. Webarchive template wayback links Articles lacking in-text citations from March All articles lacking in-text citations Use British English Oxford spelling from January The common set of standards sometimes replace the various national standards, forming a basis for global certification.
The IEC 61400-1 turbine safety standard
Wind turbines are capital intensive, and are usually purchased before they are being erected and commissioned.
This page was last edited on 26 Septemberat Wind turbine classes” Vestas.
Examples of modes of operation are normal operation, idling, and operation with yaw error. Turbine designers will typically model turbine vibrations and dynamic forces on critical lec by aeroelastic simulation programs such as HAWC2.
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Aeroelastic simulations are processed for all IEC load cases, and turbine safety is verified for each of the deterministic load cases. Languages Deutsch Edit links. Wind conditions are specified by extreme wind speed, vertical wind shear, flow inclination, turbulence and rare gust-like events.
The effective turbulence intensity includes added turbulence from wakes of neighbour turbines, and a simple wake turbulence model is provided. Wind load models are scaled differently for each wind turbine class, thus a class I A turbine is tested for higher extreme wind speed and more severe turbulence than a class II B turbine.
For small wind turbines the global industry has been working towards harmonisation of certification requirements with a “test once, certify everywhere” objective. It is, however, simpler to apply the site-assessment rules specified in another chapter of IEC Small wind turbines are defined as being of up to m 2 idc area and iwc somewhat simplified IEC standard addresses these.
IEC site assessment criteria. Updated by Heidi Serny Jacobsen.
Archived from the original on 7 October Material ice has a highly non-linearly relation to load amplitudes and thus to turbulence intensity, so a few situations with extreme turbulence may cause most of the fatigue damage. Some of these standards iex technical conditions verifiable by an independent, third partyand as such are necessary in order to make business agreements so wind turbines can be financed and erected.
This imposes simple limits on fifty-year extreme wind, flow inclination and wind shear, see Figure 1, whereas turbulence assessment is more complicated. Retrieved 18 March Retrieved from ” https: List of International Electrotechnical Commission standards. Retrieved 7 October This variation will generally decrease with wind speed, and the IEC normal turbulence model NTM accounts for this effect. 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.
The is a set of design requirements made to ensure that wind turbines are appropriately engineered against damage from hazards within the planned lifetime. This article includes a list of referencesrelated reading or external linksbut its sources remain unclear because it lacks inline citations. The extreme wind speeds are based on the 3 second average wind speed. The load type is either an ultimate load, which might instantly damage the turbine, or a fatigue load.
In addition, the accumulated fatigue 614400-1 caused by stochastic forcing is evaluated for a design life time of twenty years and compared to the material strength. In Canada, the previous national standards were outdated and impeded the wind industry, and they were updated and harmonized with by the Canadian Standards Association with several modifications.
It is also possible to use the IEC standard for turbines of less than m 2 swept area. In principle, the aeroelastic simulation could be repeated with local wind conditions at specific turbine positions.