Wind turbines are often struck by lightning because of their special shape, their tall structure and their beingplaced in the open air. Besides seriously damaging the blades, lightning results in accidents in which low-voltageand control circuit breakdowns frequently occur in many wind farms worldwide. Although some reports, such as IEC TR61400-24 and NREL SR-500-31115, have indicated a methodology for protection against such accidents, a standard solution to these problems remains to be established. The author, focusing on a method for protection of low-voltage and control circuits in a wind tower, proposed a new lightning protection system with two ring-shaped electrodes attached to the wind turbine. The proposed system has two ring-shaped electrodes of several meters diameter, one vertically attached to the nose cone and the other laterally placed at the top of the wind tower lying just below the nacelle. The pair of rings is arranged with a narrow gap of no more than 1 m in order to avoid mechanical friction during rotation of the blades and the nacelle’s circling. When lightning strikes a blade, the current reaches the upper ring from a receptor through a conductive wire. Then, the electric field between the two rings becomes high and finally sparks over and the lightning current flows downwards. The current propagates along the lower ring and the grounding wire, which is arranged outside of the wind tower rather than inside, and is safely led to a grounding electrode placed far enough away from the tower’s grounding system. In this paper, the author describes a basic experiment using a 1/100 downsized model, and also discusses the concept behind the present system. The result of the downsized experiment provides evidence of an effective advantage for lightning protection. 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
　　由于風力發電機組獨特的結構、外形、及野外安裝的客觀條件，造成機組經常受到雷擊。雷電不僅對葉片及輪轂造成嚴重損壞，還會導致其它電氣事故，如造成低壓電氣故障及控制系統故障等，雖然在相關標準中，如IEC TR61400-24和NREL SR500-31115等文件已經指出如何避免和減少雷擊事故的方法，但還應不斷地尋找的解決方案。
　　本文的作者專注研究于機組的電氣和低壓控制系統，在機組的直擊雷防護上提出了一種新型的基于環形間隙放電器的防雷系統。
　　這種系統由分別安裝在輪轂和塔筒上的環形電極組成，輪轂的環形電極于葉片內部的導雷電纜連接，塔筒的環形電極與塔筒形成可靠的電氣連接，并安裝在水平于輪轂的機艙底部。兩個環形電極的間距保持在1m以內，這樣可以避免輪轂在運動過程中與塔筒上的環形電極造成撞擊而影響機組偏航。當雷電擊中葉片時，雷電流沿葉尖接閃器及導雷電纜將雷電流傳送到輪轂上的環形電極，由于兩個環形電極間存在電位差，所以可以使兩個電極觸發形成雷電通道，最后雷電流通過他同上的環形電極泄放入地。
　　在本文描述的試驗中，實驗者采用了比例尺為1:100的風機模型進行了基本的實驗，同事對風電防雷的前瞻技術進行了討論，這個實驗為這種避雷系統的有效性進行了驗證，相關資料由日本電氣工程師協會及John Wiley& Sons公司在2006年對外發布。
　　1. Introduction
　　The installation of wind turbine has grown explosively worldwide; however, problems regarding interconnectivity to grids have arisen. It has also been pointed out that wind power generation facilities are exposed to lightning damage owing to their configurations, and so protective measures different from those needed for conventional generators are necessary. This problem has recently surfaced as an important issue [1–7].Japan, especially suffers from frequent and heavy lightning strikes, an example being the notorious ‘winter lightning’ found in coastal areas of the Sea of Japan[8]. Indeed, many turbines in Japan have been hit by lightning, and winter lightning poses a specific threat due to its intense power and electric current which are much higher than the world average [7,9]. Although some of the above-mentioned reports describe these incidents and methods of protection, there appear to have been few investigations into insulation schemes, lightning protection design and transient analysis for the latest generation of apparatus. While blade protection has been relatively well discussed [7], the behavior of the wind turbine experiencing surge propagation during a lightning stroke has yet to be clarified.
　　There is room for more work to be done in this area. In general, lightning protection for wind power generation includes a lightning pole on a nacelle, an independent lightning pole tower and a receptor on the top end of a blade. But the lightning pole on the nacelle cannot obtain enough height owing to weight and wind pressure, and an independent lightning tower greatly increases the construction costs.