Reproduction of FRP Blade Failure for Wind Power Generators by Lightning and its Mechanism

Abstract

In Japan, lightning damage to FRP blades for wind power generators is increasing, together with the increase in wind power generator installation in recent years. Lightning damage is a big issue in Japan since lightning in Japan seems to be severer than in Europe and the US. In Kochi, Shikoku, Japan, six 600-750kW grade generators have been installed, and some of them have been damaged by lightning several times. In order to solve this issue, the Kochi University of Technology received a research request of lightning protection, sponsored by the Kochi prefecture in 2002. After surveying the literature and questioning related organizations such as NREL (National Renewable Energy Laboratories) and Toray USA, experiments to reproduce lightning damage to FRP specimens were planned. The specimens prepared for this research are 1/2 size models and a 2/4 part of the full size blade. In the previous experiment, flat plate specimens of 450mm width × 2.5m length × 4mm thickness were used, and the experiments produced the damage by lightning. However, the damages were not exactly the same as the ones in the actual field. Therefore, this experiment aims to reproduce the blade failure in the actual field and to clarify the failure mechanism, using the 1/2 size blade model and full size blade specimens. The experiments were conducted mainly in the Toshiba Hamakawasaki High Voltage High Power Testing Laboratory as was made in the previous experiments. This Testing Laboratory is one of the biggest test laboratory for experiments involving high electric voltage and large current. The results showed the reproduction of the failed blades in fields, and clarified the failure mechanism.