IEC 61400

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IEC 61400 is a class of IEC international standards regarding wind turbines.

Purpose and function[edit]

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]

Small wind turbines are defined as being of up to 200m2 swept area and a somewhat simplified IEC 61400-2 standard addresses these. It is also possible to use the IEC 61400-1 standard for turbines of less than 200m2 swept area.

Harmonization[edit]

IEC, API, ISO etc. standards used to certify US offshore wind turbines

In the U.S., standards are intended to be compatible with IEC standards,[4] and some parts of 61400 are required documentation.[5][6]

The U.S. National Renewable Energy Laboratory participates in IEC standards development work,[4][7] and tests equipment according to these standards.[8] For U.S. offshore turbines however, more standards are needed, and the most important are :

  • ISO 19900, General requirements for offshore structures
  • ISO 19902, Fixed steel offshore structures
  • ISO 19903, Fixed concrete offshore structures
  • ISO 19904-1, Floating offshore structures – mono-hulls, semisubmersibles and spars
  • ISO 19904-2, Floating offshore structures - tension-leg platforms
  • API RP 2A-WSD, Recommended practice for planning, designing and constructing fixed offshore steel platforms - working stress design.[9]

In Canada, the previous national standards were outdated and impeded the wind industry, and they were updated and harmonized with 61400 by the Canadian Standards Association with several modifications.[10][11]

For small wind turbines the global industry has been working towards harmonisation of certification requirements with a "test once, certify everywhere" objective. Considerable co-operation has been taking place between UK, USA, and more recently Japan, Denmark and other countries so that the IEC 61400-2 standard as interpreted within e.g. the MCS certification scheme (of UK origin) is interoperable with the USA (for example where it corresponds to an AWEA small wind turbine standard) and other countries.

Wind Turbine Generator (WTG) Classes ( IEC 61400-1 ed.2)[edit]

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.[12]

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.[13]

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. This is the definition in IEC 61400-1 edition 2.

For U.S. waters however, several hurricanes have already exceeded wind class Ia with speeds above 156 mph, and efforts are being made to provide suitable standards.[9]

List of subclasses[edit]

  • IEC 61400-1 Design requirements[14][3]
  • IEC 61400-2 Small wind turbines
  • IEC 61400-3 Design requirements for offshore wind turbines[15][16][17]
  • IEC 61400-4 Design requirements for wind turbine gearboxes
  • IEC 61400-5 Wind turbine rotor blades
  • IEC 61400-11 Acoustic noise measurement techniques[20][21]
  • IEC 61400-12 Wind turbine power performance testing
  • IEC 61400-13 Measurement of mechanical loads
  • IEC 61400-14 Declaration of apparent sound power level and tonality values
  • IEC 61400-21 Measurement and assessment of power quality characteristics of grid connected wind turbines
  • IEC 61400-22 Conformity testing and certification[1]
  • IEC 61400-23 Full-scale structural testing of rotor blades
  • IEC 61400-24 Lightning protection
  • IEC 61400-25 Communication protocol[22]
  • IEC 61400 26 Time based availability for wind turbines
  • IEC 61400-27 Electrical simulation models for wind power generation (Committee Draft)

List compiled from a number of sources.[2][23][24]

References[edit]

  1. ^ a b c d e Woebbeking, Mike. "IEC TS 61400-22" pages 1-2 and 9 Germanischer Lloyd, 2008. Accessed: 12 March 2011.
  2. ^ a b Madsen, Peter Hauge. "Introduction to the IEC" Risø DTU National Laboratory for Sustainable Energy, 21 August 2008. Accessed: 12 March 2011.
  3. ^ a b "IEC61400-1 site assessment". Retrieved: 16 August 2012.
  4. ^ a b Dodge, Darrell M. "Development of Wind Industry Consensus Standards" National Renewable Energy Laboratory, 27 February 1996. Retrieved: 16 August 2012. Quote: "U.S. standards must be compatible with IEC standards"
  5. ^ "IEC 61400-22 Required Design Documentation". Retrieved: 16 August 2012.
  6. ^ IEC 61400-22 Required Design Documentation National Renewable Energy Laboratory[dead link]
  7. ^ NREL's technical role in standards development National Renewable Energy Laboratory[dead link]
  8. ^ "Accredited Testing" National Renewable Energy Laboratory. Retrieved: 16 August 2012.
  9. ^ a b Musial, W. D.; Sheppard, R. E.; Dolan, D.; Naughton, B. "Development of Offshore Wind Recommended Practice for U.S. Waters" Intro page National Renewable Energy Laboratory, April 2013. Accessed: 20 November 2013. OSTI ID: 1078076
  10. ^ "Updated standards propel wind energy development" page 23, Natural Resources Canada 2010. Retrieved: 16 August 2012. Quote: "previous Canadian standards were an impediment to the industry" .. "harmonized them with the IEC standards"
  11. ^ [1][dead link]
  12. ^ "Wind project planning: Wind turbine classes" Vestas. Accessed October 2011.
  13. ^ Langreder, Wiebke. "Siting of Wind Farms: Basic Aspects" Suzlon Energy. Accessed October 2011.
  14. ^ Nielsen, Morten. "Presentation of Windfarm Assessment Tool" Risø DTU National Laboratory for Sustainable Energy, December 2011. Retrieved: 16 August 2012.
  15. ^ "Wind turbines Part 3: Design requirements for offshore wind turbines" Austrian Standards Institute. Retrieved: 16 August 2012.
  16. ^ International Standard IEC 61400-3 International Electrotechnical Commission, August 2005. Accessed: 12 March 2011.[dead link]
  17. ^ Quarton, D.C. An international design standard for offshore wind turbines: IEC 61400-3 GL Garrad Hassan, 2005. Accessed: 12 March 2011.
  18. ^ "Design requirements for floating offshore wind turbines" International Electrotechnical Commission. Retrieved: 16 August 2012.
  19. ^ "Classification and Certification of Floating Offshore Wind Turbines" Bureau Veritas, November 2010. Retrieved: 16 August 2012.
  20. ^ Schröder, Sascha Thorsten / B. Holst Jørgensen. "Energy Supply Technologies: Wind Power" page 23. Risø DTU National Laboratory for Sustainable Energy, 16 November 2011. Retrieved: 17 February 2013.
  21. ^ IEC 61400-11 Acoustic noise measurement techniques IEC, 2006. Accessed: 12 March 2011.[dead link]
  22. ^ IEC 61400-25 User Group web site
  23. ^ "International Standard IEC 61400-1, Third Edition" International Electrotechnical Commission, August 2005. Accessed: 12 March 2011.
  24. ^ IEC 61400 publications International Electrotechnical Commission, August 2005. Accessed: 12 March 2011.