Classification of lightning damage to wind turbine blades

Lightning damage to wind turbine blades is of great concern to wind power installations. We investigate various issues arising from lightning damage and assess the causes through actual lightning observations as well as from high‐voltage and large‐current experiments. Although installing lightning receptors and down conductors provide a good countermeasure, blade damage can still be caused by lightning still. New techniques are needed to better protect blades from lightning surges; these may include not only better performance and layout of receptors, but also independent lightning towers and new types of blade materials. This paper provides a classification of blade damage sustained in winter lightning, ranked in severity by analyzing the many incidents of damage that have actually occurred in Japan. Moreover, a list of possible causes of damage and relative countermeasures is also presented. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An experimental study of lightning overvoltages in wind turbine generation systems using a reduced‐size model

Wind turbine generation systems are built at locations where few tall structures are found nearby so as to obtain good wind conditions, and thus, they are often struck by lightning. To promote wind power generation, lightning‐protection methodologies for such wind turbine generation systems have to be established. This paper presents the result of an experimental study of lightning overvoltages in wind turbine generation systems using a reduced‐size wind turbine model. Overvoltages observed at wavefronts of lightning surges are focused on in this study. In the experiments, lightning strokes to one of the blades and to the nacelle were considered, and voltages and currents at various positions of the wind turbine model were measured. The following points have been deduced from the results: (i) The voltage rise due to the tower footing resistance can cause a significant voltage difference between the tower foot and an incoming conductor led from a distant point. Also, a voltage difference between the bottom of down conductors installed inside the tower and an incoming conductor can be of significance. (ii) The lightning current flowing through the tower body induces voltages in main and control circuits which form loops, and the induced voltages can cause overvoltages and malfunctions. (iii) Traveling‐wave phenomena in a wind turbine generation system for a lightning strike to the tip of a blade and to the nacelle have been clarified from the measured waveforms. This information can be used for developing an EMTP simulation model of wind turbine generation systems. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 22– 30, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20466     

计算机信息系统安全防雷研究

研究了计算机信息系统的安全防雷区域的划分原则，提出了计算机信息系统防雷设备的最佳配置方案、联接方式及容量计算方法，对单级防雷和多级防雷原理进行了理论分析和实际工程应用效果的分析对比，并对防雷设计中地网接地电阻值的大小提出了新的研究见解。     

Characteristics of lightning strikes on wind turbine blades. Experimental study of the effects of receptor configuration and other parameters

The characteristics of lightning strikes on wind turbine blades have been investigated by model experiments with real turbine blades. The effects of various types of receptors, the polarities of the applied voltages, and pollution on the blade surface are clarified. Based on these experimental results, lightning protection design of actual wind turbine blades by receptors is discussed. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(3): 8–18, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21143     

农村配电网线路和设备的防雷接地保护研究

针对1起10 kV配电变压器高压侧避雷器爆炸引起的低压侧用户电击死亡事件,分析农村配电网的防雷保护和低压配电线路上用户的电气安装等问题,并提出相应的修改措施。     

基于雷电预警的UHVDC系统主动雷击防护策略

提出了基于降压运行和直流紧急功率支援的主动防护思路,分析了在特高压直流输电系统遭受雷击故障时2种方法提高电网安全运行能力的作用。利用PSASP建立了四川电网丰大运行方式下包含特高压直流输电通道的仿真模型,基于系统稳定性判据,仿真分析了雷击造成各条特高压直流输电通道单极/双极闭锁时,降压运行控制和直流紧急功率支援控制对送端电网安全稳定性的影响。研究结果对确保含特高压直流输电系统的电网安全稳定运行具有参考价值。     

Influence of wind turbulence on yaw‐control gears in wind turbine

This paper describes the influence of wind turbulence on the yaw‐control gears of the nacelle in a wind power station. The site is located on Tappi Cape in Aomori prefecture, where major wind turbulence occurs due to the strong western wind and the steep slope of the cape. This paper discusses two adjacent wind towers out of a total of eleven and clarifies the influence of wind turbulence on the leeward wind power generator. Measurements showed that the turbulence and the standard deviation frequently exceeded IEC Wind Turbine Standards. Consequently, the torque applied to the yaw‐control gears oscillated with a short time period and its magnitude was frequently greater than 4.8 ton‐m (47 kN‐m), regarded as the metal fatigue limit. By a method in which the output of the wind turbine generator is controlled, the magnitude of the oscillating torque can be reduced below the limit of material fatigue. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 15–25, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21141     

风电机组过电压保护与防雷接地设计

迄今我国尚无风电系统过电压保护和防雷接地的国家标准或行业标准,为了促进风电行业的快速发展,通过理论分析并结合工程实际,给出了风电系统中风电机组过电压保护体系和实现。该体系主要考虑直击雷保护、感应雷保护、接地装置、机组配套升压设备保护等内容,并结合风电工程实例,系统地阐述了风电系统中风电机组的过电压保护及防雷接地的方案设计及其实现,满足了工程的实际需要,对风力发电和风电场设计具有较好的指导意义。     

某风电场风能发电机组综合防雷浅析

通过对蓬莱紫荆风电场风电机组所处的特殊雷电环境以及遭受雷击后果的分析,依据《建筑物防雷设计规范》、《建筑物电子信息系统防雷技术规范》等国家现行防雷技术规范,参照国际电工委员会(IEC)防雷部分相关标准,对风电机组雷电防护进行设计和探讨,以期达到各系统的正常运行,最大限度地减少雷击损失。     

Prospective method of lightning protection schemes in distribution system

Grounding wires and enclosed ZnO elements have been incorporated generally in 6.6‐kV distribution systems by TEPCO for the reduction of lightning overvoltages. At present, the reliability to lightning surges is tolerably good. However, the facility of grounding wires is not inexpensive and its maintenance is hard due to corrosion and disconnection in some areas. A typical model simulating TEPCO field adopting enclosed ZnO elements has been developed and we have evaluated relative failure risks systematically according to conditions with and without grounding wires against lightning overvoltages. Two kinds of failures discussed in the paper are the flashover of insulation and the overduty of ZnO elements, and two kinds of induced and direct lightning overvoltages are studied in flashover. The greatest problem with no grounding wire is the increase of ZnO elements' duty, but it was demonstrated that a short partial grounding wire around ZnO elements or the selection of heavier ZnO elements provides a solution. The main objectives of this study are to clarify the relative failure risks systematically according to realistic field conditions, the risk of small stroke currents having long duration to ZnO elements' duty, and countermeasures against ZnO elements' overduty. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 1–10, 1999     

农村变电站防雷保护与接地装置设计探讨

根据对农村35 kV变电站防雷保护与接地装置设计的实践体会,就农村35 kV变电站防雷保护与接地装置设计中存在的主要问题进行探讨。指出在变电站的进线保护设计中,为便于进线防雷保护避雷线的安装,要注意线路终端与母线门型架不带角度(小于5)°。在避雷针保护范围的设计中,多年来的实践证明折线法计算能满足电力行业的要求,而且与滚球法相比具有一定的优越性。提出了在防止反击过电压和接地装置的设计中应该注意的主要问题,并指出实践中采用的对策。     

变电站二次系统防雷保护初探

变电站二次设备的防雷保护是一个新的课题．其设计思想强调以电子信息系统为保护核心,为被保护设备构建一个均压等电位系统,并通过各级电涌保护器．逐级把雷电流泄放入大地。广东省广电集团有限公司汕尾供电分公司在对110kV汕尾变电站进行自动化改造的工程实践中．根据以上设计原则并结合实际情况对变电站二次设备防雷进行选型设计,提高了系统的运行安全性和可靠性。     

Hybrid configuration of Darrieus and Savonius rotors for stand‐alone wind turbine‐generator systems

The suitable hybrid configuration of Darrieus lift‐type and Savonius drag‐type rotors for stand‐alone wind turbine‐generator systems is discussed using our dynamic simulation model. Two types of hybrid configurations are taken up. Type A installs the Savonius rotor inside the Darrieus rotor and Type B installs the Savonius rotor outside the Darrieus rotor. The computed results of the output characteristics and the dynamic behavior of the system operated at the maximum power coefficient points show that Type A, which has fine operating behavior to wind speed changes and can be compactly designed because of a shorter rotational axis, is an effective way for stand‐alone small‐scale systems. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 150(4): 13–22, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20071     

应对风电机组高压脱网的继电保护策略

在数次大规模风电机组脱网事故中,部分机组脱网是由于系统电压超过了机组过电压保护定值。此类事故一定程度上暴露出风电机组和无功补偿装置电压保护定值未能合理配合的问题,为解决此问题,应协调升压站电容器组和机组过电压保护定值,通过保护时限和保护定值两方面对二者进行配合。梳理了风电场无功补偿电容器组和风电机组的过电压保护的整定原则,研究了不同工况下机组电压与升压站母线电压的关系。通过简化和推理,提出了一种机组和升压站之间电压差值的工程计算方法,可用于风电场内过电压保护的整定。最后给出了风电机组和电容器组过电压保护定值的整定原则和配合策略。     

Dynamic behavior of an island power system with variable‐pitch wind turbines under high renewable energy penetration and high wind speed

High penetration of renewable energy in a power system may cause the problem of power dispatching and stability. The detailed dynamic behavior analysis for such a system is therefore important to the planning and operation of the power system. This study discussed the dynamic characteristics of an island power system with variable‐pitch wind turbines under high wind speed and high small hydraulic output power. The system primarily consisted of three diesel engine power generation systems, three constant‐speed variable‐pitch wind turbines, a small hydraulic induction generation system, and lumped static loads. The maximum penetration of renewable energy in this system could reach almost 60%. Detailed models based on MATLAB/Simulink were developed to cater for the dynamic behavior of the system. The results suggested that this island power system can operate stably in this operational mode with the help of variable‐pitch wind turbines. This study can serve as an important reference for planning, operation, and further expansion of island power systems. Copyright © 2014 John Wiley & Sons, Ltd.     

不同风电机组的低电压穿越能力分析

应用Matlab 7.0建立了含不同风电机组的风电场动态模型,用于研究包含恒速异步风力发电机和双馈异步风力发电机的风电场对电网的影响,通过仿真分析电网发生严重三相短路故障后不同风电机组的低电压穿越能力,以及加装静止无功补偿器(SVC)后风电机组的低电压穿越能力.比较风电机组转速、有功功率和无功功率变化情况,得出结论:双馈异步风力发电机变速平稳,低电压穿越能力较强,有利于优化电能质量.当电网发生故障时,针对风电场中的不同风电机组应采用不同的策略来提高风电机组的低电压穿越能力,维持电力系统的稳定运行.     

提高大规模风电接纳及送出的系统保护研究

为了提高酒泉风电的接纳和送出,从系统视角提出一种大规模风电接入电网线路的继电保护与控制一体化新方法。利用基于统计分析的潮流波动判据和基于本地信息量的潮流转移识别,从风电潮流波动中甄别出某重负荷线路发生了故障、判别出该线路因故障被继电保护动作切除、进而还识别出原先由故障线路承担的负荷潮流转移到了非故障线路上,并导致非故障线路过负荷。结合自适应过负荷保护,在线路安全的前提下尽可能挖掘其潜在载流能力。同时融合紧急控制功能,按实际需要切除风电,消除非故障线路的过负荷而不是切除该线路,解决连锁解网问题。在理论和仿真研究的基础上,研制并现场安装保护装置并检验所提系统保护方案的正确性。     

高压直流输电系统接地极不平衡保护改进措施研究

接地极是高压直流输电系统中最重要的组成部分之一。为了提高接地极保护可靠性,根据接地极线路参数及运行特性,提出了一种基于纵联差动保护原理的接地极不平衡保护方法。该方法将互感器装设在接地极引线的近站端和极址端,给出了纵差保护方案和保护判据,优化了保护动作策略,分析了保护动作特性。仿真结果表明,提出的接地极不平衡保护能准确辨识故障类型,准确动作隔离故障,有效降低直流系统停运概率。     

Proposal and development of radial air‐gap coreless generator suitable for small wind turbine used in urban area

Independent distributed power generation using small wind turbines is becoming more widespread as wind power generation increases. Installation of small wind turbines in densely populated urban areas is not only useful from the viewpoint of extracting wind power sources in weak‐wind areas but also for making renewable energy easier to access when power supplies are closer to consumers. It is from this point of view that the authors proposed “urban wind power generation” using a collective system with a number of small vertical wind turbines, and have developed a suitable generator for low‐speed vertical wind turbines such as a Savonius windmill. Based on a standard coreless generator, the proposed generator is designed to make the direction of the magnetic flux radial in order to install the magnets and coils on the outer end of the generator. The change of magnet composition and flux direction maximizes the speed of the flux change and output voltage within a limited space. With the above configuration, the power of the proposed generator is independent of the diameter. In this report, the authors describe and evaluate the fundamental performance of a prototype of the proposed generator. Based on the experiments, a maximum output power of 283 W was obtained. The obtained starting torque is small enough to begin rotation under weak wind conditions of no more than 1 m/s. Therefore, it is clear that the proposed “radial” coreless generator is suitable for self‐starting and producing high power at low wind speed. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 26– 34, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20695     

Decentralized model predictive‐based load‐frequency control in an interconnected power system concerning wind turbines

This paper presents a load‐frequency control (LFC) design using the model predictive control (MPC) technique in a multi‐area power system in the presence of wind turbines (WTs). In the studied system, the controller of each local area is designed independently such that the stability of the overall closed‐loop system is guaranteed. A frequency response model of the multi‐area power system including WTs is introduced, and physical constraints of the governors and turbines are considered. The model was employed in the MPC structures. Digital simulations for a two‐area power system are provided to validate the effectiveness of the proposed scheme. The results show that with the proposed MPC technique the overall closed‐loop system performance shows robustness in the face of uncertainties due to governor and turbine parameter variation and load disturbances. A performance comparison between the proposed controller with WTs and MPC without WTs and a classical integral control scheme is carried out, confirming the superiority of the proposed MPC technique with WTs. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.