IEC 61400-1:2005 pdf free download – Wind turbines
6.1General
The external conditions described in this clause shall be considered in the design of a windturbine.
Wind turbines are subjected to environmental and electrical conditions that may affect theirloading，durability and operation. To ensure the appropriate level of safety and reliability,environmental,eiectrical and soil parameters shall be taken into account in the design andshall be explicitly stated in the design documentation.
The environmental conditions are further divided into wind conditions and other environmentalconditions. The electrical conditions refer to the electrical power network conditions. Soilproperties are relevant to the design of wind turbine foundations.
The external conditions are subdivided into normal and extreme categories. The normalexternal conditions generally concern recurrent structural loading conditions, while the extremeexternal conditions represent rare external design conditions. The design load cases shallconsist of potentially critical combinations of these external conditions with wind turbineoperational modes and other design situations.
Wind conditions are the primary external conditions affecting structural integrity. Other environ-mental conditions also affect design features such as control system function，durability,corrosion, etc.
The normal and extreme conditions, which are to be considered for design according to windturbine classes, are prescribed in the following subclauses.
6.2 Wind turbine classes
The external conditions to be considered for design are dependent on the intended site or sitetype for a wind turbine installation. Wind turbine classes are defined in terms of wind speedand turbulence parameters. The intention of the classes is to cover most applications.Thevalues of wind speed and turbulence parameters are intended to represent many different sitesand do not give a precise representation of any specific site, see 11.3. The wind turbineclassification offers a range of robustness clearly defined in terms of the wind speed andturbulence parameters.Table 1 specifies the basic parameters, which define the wind turbineclasses.
A further wind turbine class, class S, is defined for use when special wind or other externalconditions or a special safety class,see 5.3, are required by the designer and/or the customer.The design values for the wind turbine class S shall be chosen by the designer and specified inthe design documentation. For such special designs，the values chosen for the designconditions shall reflect an environment at least as severe as is anticipated for the use of thewind turbine.
The particular external conditions defined for classes l,ll and lll are neither intended to coveroffshore conditions nor wind conditions experienced in tropical storms such as hurricanes,cyclones and typhoons.Such conditions may require wind turbine class s design.
In addition to these basic parameters，several other important parameters are required tocompletely specify the external conditions to be used in wind turbine design. In the case of thewind turbine classes lg through llc, later referred to as the standard wind turbine classes, thevalues of these additional parameters are specified in 6.3,6.4 and 6.5.
The design lifetime for wind turbine classes l to lll shall be at least 20 years.
For the wind turbine class s the manufacturer shall, in the design documentation, describe themodels used and values of design parameters. Where the models in Clause 6 are adopted,statement of the values of the parameters will be sufficient. The design documentation of windturbine class s shall contain the information listed in Annex A.
The abbreviations added in parentheses in the subclause headings in the remainder of thisclause are used for describing the wind conditions for the design load cases defined in 7.4.