Environmental Engineering Reference
In-Depth Information
situational load cases that include numerous external wind and operational scenarios and
events. Some of these are
deterministic
, discrete events to be simulated. Others are
proba-
bilistic
in nature and require multiple
stochastic time domain simulations
from which the ex-
treme loading events must be extrapolated. All inal load cases to be used in type certiication
are expected to be simulated using a dynamically coupled aeroelastic model of the full wind
turbine. This model must have been validated using prototype test data.
The standard document provides detailed computational descriptions of the determinis-
tic wind models, such as the extreme coherent gust with direction change, the extreme wind
direction change model, the extreme wind speed model, the extreme wind shear model, and
the normal wind proile model. The standard also provides mathematical models for nor-
mal and extreme turbulence. The application of these models for calculating the resulting
loads and stresses on
turbine components requires a full-ield simulation of the three
dimensional
turbulent low ields in time and space across the swept area of the rotor. The
turbulent variations are deined to be the random variations in the wind ield from a 10-
minute mean low. The standard provides information on two models that may be used for
turbulence calculations.
The standard also provides information on how to account for wake turbulence effects
from neighboring turbines in a wind power station when performing fatigue calculations.
Computer Simulation
The computer simulation of the operational environment of a modern wind turbine has
markedly advanced over the past 30 years. Techniques for performing the complex analy-
ses required by the IEC standards have been developed by the U.S. national laboratories in
collaboration with laboratories in Europe. Documentation of the theory and practical ap-
plication of these analysis techniques with description of the related computer methods is
available from the National Renewable Energy Laboratory in Golden, Colorado, and Sandia
National Laboratories in Albuquerque, New Mexico.
Measurement and Testing Standards
A second suite of standards has been developed by the IEC for the measurement and
testing of wind turbines, as follows:
1) IEC 61400-1, Wind turbines - Part 1: Design requirements
2) IEC 61400-2, Wind turbines - Part 2: Design requirements for small wind
turbines
3) IEC 61400-3, Wind turbines - Part 3: Design requirements for offshore wind
turbines
4) IEC 61400-11 Wind turbine generator systems - Part 11: Acoustic noise mea-
surement techniques
5) IEC 61400-12, Wind turbines - Part 12: Power performance measurements of
electricity producing wind turbines
6) IEC/TS 61400-13, Wind turbine generator systems - Part 13: Measurement
of mechanical loads
7) IEC/TS 61400-14, Wind turbines - Part 14: Declaration of apparent sound
power and tonality values
8) IEC 64100-21, Wind turbines - Part 21: Measurement and assessment of
power quality characteristics of grid connected wind turbines
9) IEC/TS 61400-23, Wind turbine generator systems - Part 23: Full scale struc-
tural testing of rotor blades
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