External Condition Models from the International Electrotechnical Commission Safety of Wind Turbines Standards (1400-1)

The International Electrotechnical Commission (IEC) TC88 Working Group 7 formed a subcommittee to evaluate the external wind condition models defined in the recently released standard for 'Wint Turbine Generator Systems, Part I: Safety Requirements' 1400-I. These models define design turbulence conditions, extreme gust transients, extreme wind direction transients and extreme shear transients aswell as other normal and extreme conditions. The subcommittee solicited extreme wind condition data from countries throughout the world. The data were compared to the 1400-I standard models. Techniques were developed to extract the statistics of parameters such as maximum gust magnitudes, minimum gust rise times, and extreme wind shears. These data were used to modify the IEC models to be morerepresentative of typical field conditions. The original models, data used for comparison, and the new models are presented.