冬季雷放電進展モデルによる風力発電所に設置される独立避雷塔の雷遮へい効果予測

摘要

日本海沿岸地域の風力発電設備では，冬季に発生する上向き雷の直撃による被害が多く，この被害を低減させることを目的とした独立避雷塔（以下，避雷塔と呼ぶ）が建設されることがある。避雷塔の建設には多額の費用が掛かることから，計画段階において十分な費用対効果の検討を行わなければならない。避雷塔による雷遮へい効果予測法として保護角法や電気幾何学モデルが用いられることがあるが（1）（2），これらは本来，下向き雷に適用されるものであり，理論的には上向き雷に対して適用できない。上向き雷の雷遮へい効果の予測法としては，冬季雷放電進展モデル（以下，ULPモデル（UpwardLeaderProgressionmodel）と呼ぶ）が相原により提案されているが（榊，雷遮へい効果に関する観測例が非常に少なく，予測計算結果についての検証 は十分とは言えない。%The wind power stations on the coast of the Japan Sea have high risks to be damaged by upward lightning in winter, so that sometimes lightning towers have been set up as a countermeasure. The upward leader progression model (ULP model) is proposed as a prediction method of lightning protective effect of upward lighting in winter. However, there are only few observational data, so that validation examples of lightning shielding effect using this prediction method are few. One wind turbine and one lightning tower have been set up at the Uchinada wind power station, and the lightning observations have been continued and 77 observational data have been reported so far. In this paper, we have made a comparative study of the lightning ratios estimated by ULP model and by observational data. Although there were some cases that had big differences in lightning ratio due to the wind direction, the final result of general lightning ratio was almost the same. Regarding the wind direction distribution used in ULP model, there were some differences in number between proposed wind direction distribution and observed wind direction distribution. However, it doesn't have a great impact on the calculation of the lightning ratio due to the differences in this paper.