Though the third solution, the receptor on a blade, recommended in IEC61400-24 [5], appears the best solution for lightning protection, it is not a complete solution. Despite the existence of such receptors, dielectric accidents still occur on wind power turbines including blades, the generator, the transformer and lowvoltage circuits [7].
    According to an IEC report [5], the most frequent accident is dielectric breakdown on low-voltage circuits including electric and telecommunication equipment. In general, electrical and electronic equipment for wind power generation are set up close to or inside a wind tower. Once lightning strikes the wind turbine, assuming that it hits a receptor of one of the blades, a lightning current surge propagates through a down-conductor in the blade, a carbon brush or arc horn near the bearings,and the grounding conductor inside a wind tower (or,in another case, the current may flow through the conductive tower itself). The low-voltage circuit in the wind turbine is easily broken by electromagnetic induction in such a situation. Considering the above, the author proposes a novel lightning protection system that has two ring-shaped electrodes. The principal concern of the proposed system is to prevent the lightning surge from affecting the wind turbine as well as the nacelle and the tower.
    This paper discusses an impulse experiment utilizing the proposed system in a downsized wind tower accurately simulating an actual 2 MW wind turbine on a 1/100 scale. Attaching the proposed ring-shaped electrodes to the downsized wind turbine, the author demonstrates that the system provides effective lightning protection.

　　1. 前言
　　隨著風(fēng)電產(chǎn)業(yè)的迅猛發(fā)展，全球裝機(jī)量的激增，機(jī)組的并網(wǎng)問題和雷電的防護(hù)問題逐步得到了業(yè)界的重視，由于機(jī)組所處的安裝條件都比較惡劣，并且其自身的結(jié)構(gòu)特點(diǎn)，也是也在環(huán)境中較易遭到雷擊。因此，發(fā)明一種新型的直擊雷防護(hù)措施，已經(jīng)成了一種必須的措施。
　　雷電對(duì)機(jī)組的影響已經(jīng)暴露出來，日本經(jīng)常會(huì)受到嚴(yán)重的雷擊侵襲。而最有名的的應(yīng)該是日本沿海地區(qū)獨(dú)有的冬季雷暴。實(shí)際上，在日本的沿海的風(fēng)力發(fā)電場(chǎng)每年都受到嚴(yán)重的雷電影響，同時(shí)由于日本冬季雷的電流強(qiáng)度高于世界平均雷電流強(qiáng)度，所以其威力和破壞力也是巨大的。
　　盡管按照相關(guān)的標(biāo)準(zhǔn)采取了一定的防護(hù)措施，但在對(duì)于葉片而言仍沒有更好的防護(hù)手段，當(dāng)雷電擊中機(jī)組后雷電流的傳導(dǎo)還存在很多不確定性。
　　所以說在風(fēng)力發(fā)電雷電防護(hù)領(lǐng)域還有很多的工作需要進(jìn)一步完善，一般來講，機(jī)組的防雷系統(tǒng)包括：機(jī)艙接閃器（測(cè)風(fēng)支架）、葉片接閃器、由于機(jī)艙上接閃器的高度和角度不能滿足防護(hù)需要，單獨(dú)設(shè)計(jì)避雷塔的費(fèi)用也較高；盡管葉片上配置有接閃器，也被IEC61400-24這一技術(shù)屬性文件明確提出，并作為一種通用方案，但是這并不是最完整有效的防護(hù)方法。無論葉片上是否有設(shè)計(jì)接閃器，對(duì)于機(jī)組的變槳、主控、發(fā)電機(jī)、變壓器等低壓電控設(shè)備的雷擊事故依然發(fā)生。IEC的一篇技術(shù)性文章指出：雷電對(duì)機(jī)組的影響主要集中在低壓電控系統(tǒng)和通信系統(tǒng)，一般來說只要機(jī)組中存在低壓電子類裝置，在雷電發(fā)生時(shí)，低壓電控設(shè)備都是受到雷電電磁脈沖的影響及直接在線路上產(chǎn)生的浪涌的侵襲。
　　考慮到機(jī)組的特殊情況，作者提出了一種利用兩個(gè)環(huán)形電極構(gòu)成的間隙放電器組成的直擊雷防護(hù)系統(tǒng)，這種系統(tǒng)最擔(dān)心的問題是如何保證雷電流不進(jìn)入輪轂及機(jī)艙，這部分在文中將作為重點(diǎn)討論。通過一個(gè)比例尺為1:100參照實(shí)際的2MW風(fēng)力發(fā)電機(jī)組制作一個(gè)模型，并采用這種防雷系統(tǒng)，通過雷擊實(shí)驗(yàn)的方式驗(yàn)證這套系統(tǒng)的有效性和優(yōu)勢(shì)。
 

　　2. Proposal of the Novel Lightning Protection System
　　Figure 1 is a conceptual illustration of a conventional system and the proposed system of lightning protection for wind turbines. Generally, in the conventional system,the lightning current flows from one of the receptors installed on the top end of a blade to the ground via a down-conductor in the blade, brush or arc-horn near the bearing, and a grounding-wire (or sometimes the body of the tower itself).