5. Conclusions

　　In this paper the author has proposed a novel method that utilizes two ring-shaped electrodes for lightning protection of wind turbines. The most important and innovative point of the proposed system is a pair of ringshaped electrodes arranged with a narrow gap, where the air discharges to flow the surge current when a lightning strikes the wind turbine.1/100 downsized model of a wind turbine with ring electrodes was manufactured. The results of impulse experiments clearly showed that the proposed model can operate safely.
Especially, when the gap between the two rings is larger than the distance between the upper ring and the nacelle, it is clear that a spark-over certainly occurs and the lightning protection system functions satisfactorily.The author is also investigating FDTD electromagnetic calculations for the present model [10,11].It was confirmed that the results of the calculations also agree well with the experimental results.
 problems remain for the proposed method. For example, the method of fixation and installation costs need resolving from a civil engineering viewpoint. Also, any adverse impact on power generation capacity should be discussed from the viewpoint of fluid dynamics. However, in respect of lightning protection, i.e. utilized capacity and generating cost, the proposed system can be expected to maintain the reliability and safety of operations for wind power generation.
Acknowledgements
The author thanks Dr. Matsubara Ichiro, former lecturer of Osaka University, for his help in the operation of impulse testing and for a fruitful discussion on the methodology of lightning protection. The author also thanks Mr. Yoshioka Takuma, Mr. Fujii Toshiaki and Mr. Yamashita Shogo, graduate and undergraduate students of Kansai University, for their help in the impulse tests.

　　5. 結論

　　在這篇文章中作者提出了新型的利用環形電極間隙放電器作為風力發電機組直擊雷防護的一種方法，其中最重要和具有創新性的點在于如何控制兩個環形放電器的間距，使雷電通過間隙時不受風速對電流弧的影響，通過1:100的風機模型及模擬雷擊實驗的結果清楚的表明這種方式是可行的、安全的。雖然在環形電極間隙距離大于輪轂環形電極于機艙間距時會造成輪轂環形電極與機艙的放電，但并不影響該套方案的有效性，通過后續的優化方案這種防雷系統的效果也是能夠令人滿意的。同時作者還在運用FDTD時差法計算，間隙通過雷電流時的電磁抵消情況，但可以肯定的是電磁能量的抵消情況應該與實驗結果相吻合。
　　當然這套防雷系統仍存在一些問題，例如這個系統的定位和安裝需要從工程安裝角度來解決，并且安裝后可能對機組的整體氣動性能方面會存在怎樣的影響，還需要進一步討論。無論如何，這種方案的提出對于機組的雷電防護、實際有效性、安全性能和可實施性都被寄予了很大希望。
特別感謝
　　作者感謝大阪大學前講師Matsubara Ichiro博士，在雷電脈沖測試實驗的執行中以及機組的防護方法上提出富有成效的建議以及幫助。同時還要感謝Yoshioka Takuma先生、Fujii Toshiaki先生和Yamashita Shogo先生這些関西大學畢業和沒有畢業學生在雷擊實驗中給予的幫助。