Figure 6 presents an example of the results of an impulse test using the 1/100 downsized wind turbine model with the proposed ring-shaped electrodes. As shown in the figure, spark-over successfully occurred between the two electrodes, showing that the lightning current was safely led to a grounding electrode through the outer down conductor.In another case shown in Fig. 7, the lightning struck backward of the wind turbine.
Thus, the result of the impulse test demonstrated that the proposed two ring-shaped electrode system is effective for lightning protection for electrical and electronic devices in a wind turbine.On the other hand, the result shown in Fig. 8 is an example of an unsuccessful case. In this case, where the gap between two rings, g, is less than the distance between the upper ring and the nacelle d, spark-over often tends to occur between the upper ring and the nacelle and the lightning current unexpectedly rushes to the inside or surface of the nacelle and the tower.
This may cause the breakdown or burnout of low-voltage and control circuits installed in a wind turbine. Moreover,Fig. 9 shows another type of an unsuccessful result,where the lightning directly struck backward of the nacelle in spite of the receptor on the blade.The graphs shown in Fig. 10 summarize the aboveresults. Graphs of positive and negative lightning currents clarify that the gap for the two rings should be designed to be lower than the distance between the upper ring and the nacelle.
Although the result shows that a lower gap may make for a safer operation, the best solution needs to be considered from standpoints including the method of fixation, the weight of materials, installation costs and the effect of flexural oscillation of the rings during rotation of the blades.

　　4. 對模型進行雷擊測試
　　圖6中展示了模型進行雷電沖擊的結(jié)果。實驗表明，在輪轂的環(huán)形電極于塔筒的環(huán)形電極之間產(chǎn)生了點火花，表明雷電流通過間隙放電器進行放電。在圖7中展示了雷電擊中葉片的后緣，而兩個環(huán)形電極做組成的間隙放電器同樣觸發(fā)并導(dǎo)通，由此證明，這種環(huán)形電極組成的間隙放電器是有效的。但圖8、9中也出現(xiàn)了不成功的個案，圖8中由于兩個環(huán)形電極之間的距離問題導(dǎo)致雷電流通過輪轂的環(huán)形電極于機艙發(fā)生閃絡(luò)，并沒有通過塔筒上的環(huán)形電極；此外，在調(diào)整角度后雷電還是擊中了機艙尾部，并沒有擊中機艙上的接閃器和葉片接閃器，雖然擊中了機艙但可以看出兩個環(huán)形電極間依然形成了電流通道，在這種條件下可能會導(dǎo)致機組測風(fēng)系統(tǒng)和低壓控制系統(tǒng)的損壞。圖10中匯總了以上的實驗結(jié)果，表明兩個環(huán)形電極間隙的距離都應(yīng)設(shè)計成小于輪轂與機艙之間的距離。
　　雖然實驗取得了成功，并且表明調(diào)整間隙距離可以達(dá)到防雷保護的目的，但最好的解決方案仍需要進一步優(yōu)化，包括固定的方式，電極的材料、安裝方式，兩個環(huán)形電極在動態(tài)旋轉(zhuǎn)中的傾角擺動及誤差率產(chǎn)生的影響。