Atmospheric pressure plasma shield for protecting wind power generator from lightning stokes

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With increase in number of wind power generators, the lightning damage on the windmill blade becomes a serious problem. Although many types of lightning protection methods such as a lightning rod and a tower with rod, a grounded metal receptor embedded in a tip of the blade have been installed to reduce the lighting damage but have not sufficient effect. In this study, more active protection method using space charge around the blade or water film covered on the surface has been proposed and examined by applying lightning impulse voltage to the small blade models. The following results are obtained using lightning impulse voltage having 200-300 kV peak values.The surface of model insulator was charged by the ion wind generated by the wire corona discharge. It was found that the electric discharge channel was formed away from the surface when the polarity of the accumulated charge on the insulator was same as the applied voltage polarity, while the discharge extended around the insulator with opposite polarity. 50% flashover voltage increased when the space charge that voltage polarity was same to the impulse voltage, while decreased when the polarity reversed.In addition to the surface and space charge effect from the view point of the lightning protection, another method was developed using water films covering the surface of the dielectric materials. The discharge developed on the surface of the water when the conductivity of the water was smaller than one micro S/cm. In this case, the water breakdown was not observed at least over 0.25 mm thickness of water film. But with thinner and higher conductivity water film, the discharge current flowed in the water directly and the surface discharge was not expanded around the breakdown point.