ANewLightningProtectionSystemforWindTurbinesUsingTwoRing-ShapedElectrodes

　　一种基于环形间隙放电器的新型风力发电机组防雷系统

　　作者：YasudaYoh翻译：庄严

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.

　　由于风力发电机组独特的结构、外形、及野外安装的客观条件，造成机组经常受到雷击。

　　雷电不仅对叶片及轮毂造成严重损坏，还会导致其它电气事故，如造成低压电气故障及控制系统故障等，虽然在相关标准中，如IECTR61400-24和NRELSR500-31115等文件已经指出如何避免和减少雷击事故的方法，但还应不断地寻找的解决方案。

　　本文的作者专注研究于机组的电气和低压控制系统，在机组的直击雷防护上提出了一种新型的基于环形间隙放电器的防雷系统。

　　这种系统由分别安装在轮毂和塔筒上的环形电极组成，轮毂的环形电极于叶片内部的导雷电缆连接，塔筒的环形电极与塔筒形成可靠的电气连接，并安装在水平于轮毂的机舱底部。两个环形电极的间距保持在1m以内，这样可以避免轮毂在运动过程中与塔筒上的环形电极造成撞击而影响机组偏航。当雷电击中叶片时，雷电流沿叶尖接闪器及导雷电缆将雷电流传送到轮毂上的环形电极，由于两个环形电极间存在电位差，所以可以使两个电极触发形成雷电通道，最后雷电流通过他同上的环形电极泄放入地。

　　在本文描述的试验中，实验者采用了比例尺为1:100的风机模型进行了基本的实验，同事对风电防雷的前瞻技术进行了讨论，这个实验为这种避雷系统的有效性进行了验证，相关资料由日本电气工程师协会及JohnWiley&Sons公司在2006年对外发布。

　　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.
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

　　随着风电产业的迅猛发展，全球装机量的激增，机组的并网问题和雷电的防护问题逐步得到了业界的重视，由于机组所处的安装条件都比较恶劣，并且其自身的结构特点，也是也在环境中较易遭到雷击。因此，发明一种新型的直击雷防护措施，已经成了一种必须的措施。