Estimation of lightning current amplitudes incident to wind turbines in exposed locations

This paper proposes a novel and comprehensive methodology for estimation of lightning current amplitudes, which are incident to wind turbines (WT) at lightning‐exposed locations, i.e., hilltops. The proposed methodology takes into the account the following aspects related to WT lightning incidence: (i) site topology and keraunic level, (ii)statistical nature of lightning currents, (iii) WT effective height, (iv) dependence of lightning current amplitudes on the WT effective height, (v) influence of an upward‐initiated connecting streamers interaction with a downward‐propagating step leader on the WT lightning attractiveness, and (vi) both downward and upward lightning strikes and their relative contribution in relation to the WT effective height. This methodology could be perceived as beneficial in providing relevant lightning‐current amplitudes—particularly at lightning‐endangered locations and wind farm sites characterized by high soil resistivity—for wind turbine and wind farm overvoltage protection and backsurge studies, as well as the WT grounding systems transient analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Monte Carlo analysis of wind farm surge arresters risk of failure due to lightning surges

This paper presents a Monte Carlo procedure intended for the assessment of the metal-oxide (MO) surge arresters risk of failure in onshore wind farms. It focuses on the energy withstand (absorption) capability of the MO surge arresters in relation to lightning surges and in terms of their risk of failure assessment. Presented methodology accounts for the fact that the lightning itself is stochastic in nature and that the MO surge arrester energy capability is a statistical quantity. The well-known backsurge phenomenon is employed as a means for studying the MO surge arresters energy stresses due to lightning surge transients (in onshore wind farms), where the associated transient (i.e. high-frequency) models of particular wind farm components feature prominently. Necessary numerical simulations are carried-out with the well-known EMTP-ATP software package. This procedure could be seen as beneficial in selection of the optimal MO surge arrester energy withstand capability for wind farm projects situated in areas marked with high keraunic levels and/or having high soil resistivity.     

风电场防雷接地系统的施工工艺分析

雷击事故在风电场中时有发生,为避免雷击事故中冲击电流对风力机的损害,风力机的防雷接地系统至关重要。文中结合大唐长清风电场一期工程采取的防雷接地系统方法,对风电场降防雷接地系统的施工工艺进行阐述,通过对施工工艺的分析及接地电阻阻值的测量,得出风场中各风机的接地电阻介于2．95—3．69Ω之间,说明采用多种降阻措施相结合的方法能有效的起到降低电阻的作用,同时也证明该风电场的防雷接地系统施工工艺是满足设计要求的。     

Assessment of lightning current parameters suitable for wind turbine overvoltage protection analysis

A selection procedure for determining the lightning current parameters, suitable for wind turbine overvoltage protection analysis, will be presented in this paper. It will be based on the mathematical model that accounts for the wind turbine geometry, keraunic level, statistical distribution of lightning current parameters and correlation between statistical variables defining lightning current waveshape. Theoretical analysis will be backed up by the most recent propositions of parameters that define statistical distributions and thereafter applied on the concrete wind turbine example. Subsequently, obtained results would provide insight into the selection procedure for the lightning current parameters (i.e., amplitude, front duration, wave duration and polarity), associated with lightning stroke incidence to wind turbines. Emphases will be given to the modern new‐generation wind turbines. This selection procedure could be subsequently applied in the analysis (and design) of the wind turbine and wind farm overvoltage protection, with emphasis on the so‐called back‐surge phenomenon. Copyright © 2011 John Wiley & Sons, Ltd.     

Protection of wind energy systems against the indirect effects of lightning

This paper is concerned with the protection of wind energy systems against the indirect effects of lightning. As wind energy is gaining increasing importance throughout the world, lightning damages involving wind energy systems have come to be regarded with more attention. Nevertheless, there are still very few studies in Portugal regarding lightning protection of wind energy systems using models of the Electro-Magnetic Transients Program (EMTP). Hence, a new case study is presented in this paper, based on a wind turbine with an interconnecting transformer, considering that lightning strikes the soil near the tower at a distance such that galvanic coupling occurs through the grounding electrode. Computer simulations obtained by using EMTP-RV are presented and conclusions are duly drawn.     

Analysis and suppression measures of lightning transient overvoltage in the signal cable of wind turbines

Lightning strikes are a major threat to the secure operation of wind turbines. When lightning strikes a wind turbine, the lightning current flows through the blade and the tower and then the induced overvoltage will damage sensors and signal cables. In this study, a comprehensive transient surge impedance model of a wind turbine was built to analyze the causes of the overvoltage in the signal cable. The model that studies the overvoltage caused by both capacitive coupling and electromagnetic induction included the blade, nacelle, tower, signal cable, power cable, and grounding system using π networks. The influences of the cable shielding layer, soil resistivity, and lightning current waveform on the overvoltage were also analyzed. Then, 2 overvoltage suppression measures, ie, grounding at 2 ends of the outer shielding layer and installation of a surge protective device, were tested. Results show that a signal cable with double shielding layers reduced the overvoltage in the signal cable, and higher soil resistivity resulted in increased voltage on the tower base. In addition, the peak and the front time of the lightning current significantly influenced the overvoltage on the tower and the cable. The effectiveness of the 2 suppression measures was also verified. The calculation results will provide guidance for a reasonable lightning protection design.     

线路杆塔接地装置雷电冲击特性仿真计算与模拟试验

杆塔接地装置的冲击接地电阻值直接影响输电线路的防雷效果,降低杆塔冲击接地电阻是降低线路雷击跳闸率的有效措施。采用ATP EMTP仿真计算和模拟雷电冲击试验的方法,对杆塔接地装置的雷电冲击特性进行了研究,设计了一种改进型接地装置。经仿真分析验证,在不改变接地装置覆盖面积的情况下,该装〖JP2〗置比普遍使用的接地装置型式具有更好的雷电冲击特性,可作为高土壤电阻率地区改善线路防雷的有效途径。     

山区送电线路防雷保护措施的探讨

探讨了山区送电线路雷电“绕击”事故发生的地理、地貌和气象特征,以及山区送电线路在防止“反击”及“绕击”事故方面存在的不足,提出了“侧向避雷针”防止绕击的防雷保护新措施,以及降低杆塔接地电阻防止“反击”事故、采用线路避雷器等山区送电线路防雷的综合技术措施.     

配电变压器“双地网”防雷有效性研究

从实际出发,分析了配电变压器采用"双地网"接地方式所引起的故障,计算得出了电源防雷箱防雷效果不明显,双地网并不能够有效隔离高、低压接地网的结论。并以此为中心,分析了配电变压器防雷思路,提出了有效的配电变压器防雷方法,建议在配电变压器防雷保护中将"双地网"改成"三点一地"接线方式,高、低压侧均装设避雷器。     

Impact study of short-circuit calculation methods on the design of a wind farm's grounding system

Safe operation of a wind farm (W/F), under fault conditions, requires a grounding study to ensure protection against developed voltages (step and touch). A key stage in the design of a wind farm's grounding system is to determine the maximum ground fault current. The aim of this work is to examine how different short-circuit calculation (SCC) procedures affect the calculation of developed voltages (step and touch) at a wind farm and therefore the provided level of safety. For this purpose, the response of the interconnected grounding system of an actual wind farm is calculated, under fault conditions, using three alternative SCC methods and the results obtained concerning violation or not of safety criteria are presented.     

输电线路防雷接地技术研究

针对防雷接地技术是输电线路防雷措施实现的关键,结合福建省输电线路防雷技术的特点,分析了接地电阻值对输电线路防雷的影响,提出了提高防雷接地技术水平及降低防雷接地电阻的具体措施,在工程应用上有较强的推广价值。     

海上风电机组不同基础自然接地体的比较研究

海上风力发电机组接地网结构、所处环境等与陆上风力发电机组有显著差异。为研究海上风电机组基础作为自然接地体的问题,分别建立了单桩基础、单柱三钢桩基础、高桩承台基础和导管架基础4种地网形式的计算模型,将模型的每一个导体进行分段,再通过复镜像法求解每一段导体的格林函数,最后通过叠加定理求解基础的接地阻抗,并综合分析了典型水位变化对接地阻抗的影响。结果表明,利用海上风力发电机基础作为自然接地体能够满足电气工程生产和安全的需要,可为海上风电机组接地设计提供参考。     

关于燃气管道设备防雷的相关措施

介绍了雷电的危害性和其形成特点及雷击对燃气设备和管网的危害,并提出了相关的有针对性的雷击防护措施。从而导出燃气管道防雷接地的重要性及防雷接地的具体做法,并提醒有关部门应配合做好燃气管道的防雷接地工作,以确保管道燃气使用的安全性和可靠性。     

Lightning protection for wind turbine blades and bearings

The protection of wind turbines from lightning damage is increasingly important as they increase in size and are placed in locations where access to carry out repairs may be difficult. As blades are the most common attachment point of lightning, they must be adequately protected. In addition, the passage of lightning current through wind turbine bearings introduces a risk of lightning damage to these vital components. Investigations relating to the improvement of blade lightning protection systems have been carried out, including experiments designed to address the difficult problems involved in the protection of hydraulic cylinders used for tip brake control. Work has also focused on the ability of lightning current to cause damage to wind turbine bearings. The work has been a mixture of computer simulations and experimental testing using high‐voltage and high‐current facilities. Copyright © 2001 John Wiley & Sons, Ltd.     

光伏系统雷电防护特性仿真分析

由于光伏系统具有面积较大、暴露设备较多且需考虑直击雷防护装置阴影对太阳能电池板的遮挡影响等特点,因此其雷电屏蔽与传统电站存在差异。为更深入地了解光伏系统的雷电防护特性,结合光伏系统结构和雷电侵入途径,采用ATPDraw仿真软件,对光伏阵列及其电气设备进行建模,仿真计算了雷击光伏阵列不同位置、不同雷电流幅值及不同接地电阻情况下光伏阵列的损坏程度和对光伏系统内部设备过电压的影响,并根据计算结果提出了光伏系统雷电防护的重点。     

输电线路杆塔辅助接地网降阻效率及影响因素研究

输电线路杆塔接地网能够有效降低接地网接地阻抗,保证雷击电流安全地流入大地,实际杆塔施工过程中存在地形受限、盲目施工、降阻效率低等问题.对此,采用防雷接地领域中的CDEGS软件建立双边、单边、方框、垂直4种辅助接地网形式,通过改变外延长度、电流频率、土壤电阻率及土壤结构等因素分析比较4种辅助接地网的散流特性和降阻效率,进...     

Analytical technique of lighting surges induced on grounding meshof PWR nuclear power plant

It is noted that an analytical technique is needed to make a qualitative and predictive evaluation of transient voltages induced on local grounding meshes and instrumentation cables by a lightning strike on a lightning rod in a PWR (pressurized water reactor) power plant. An experiment with lightning surge impulses in a PWR power plant was set up to observe lightning-caused transient voltages. Experimental data are compared with EMTP (electromagnetic transient program) simulation results, and an improved simulation method is developed. The improved method provides a good estimation of induced voltages on grounding meshes and instrumentation cables. An accuracy factor of 3-5 was reached     

A new method for spatial allocation of turbines in a wind farm based on lightning protection efficiency

Existing studies of the spatial allocation of wind farms are typically based on turbine power generation efficiency and rarely consider the damage caused by lightning strikes. However, lightning damage seriously affects the economic performance of wind farms because of the high cost of repairing or replacing damaged blades. This paper proposes a method for the spatial optimization of multiple turbines based on lightning protection dependability. Firstly, the lightning protection efficiency of turbine blade protection systems is analyzed by combining the physical mechanisms of lightning leader progression with a conventional electro‐geometric model to develop an electro‐geometric model of turbine blades (EGMTB). Then, the optimized spatial allocation of multiple turbines in a wind farm is investigated using the EGMTB. The results are illustrated from an example wind farm with 1.5 MW turbines, which shows that the optimal spacing between two turbines perpendicular to the prevailing wind direction L_⊥ is 4R‐6R, where R is the length of a turbine blade. This spacing is shown to effectively shield turbine blades from lightning damage over a wide range of lightning currents (>26‐60 kA). Note that, the suggested L_⊥ will be smaller considering the influence of lightning polarity as it takes more difficulty developing upward leader (UL) in the condition of positive lightning striking. Experiments verify the effectiveness and correctness of this method.     

Choosing configurations of transmission line tower grounding by back flashover probability value

There is a considerable number of works devoted to electrical characteristics of grounding. These characteristics are important in general. However, in application to grounding of transmission line towers they are not enough to determine what grounding construction is preferable in some particular case, because these characteristics are calculated or measured apart from the grounded object, and only limited number of current (or voltage) source waveforms is used. This paper indicates reasons in favor of the fact that to choose the optimum design of grounding, the calculation model should include the tower as it is. The probability of back flashover, which provides both qualitative and quantitative estimate of the grounding structure efficiency, can be taken as the criterion for the grounding design. The insulation flashover probability is calculated on the basis of engineering method, which evaluates breakdown strength of insulation for nonstandard waveshapes, and probability data on lightning currents. Different approaches are examined for identifying the back flashover probability, as not only amplitudes but also other parameters can be taken into account. Finite-difference time-domain method is used for calculations of transients. It is found that lightning current waveform can greatly influence calculated back flashover probability value.     

Lightning attachment characteristic of wind turbine generator: Experimental investigation and prediction method based on simulations

As the height of wind turbine increases, the lightning strike accident has become a non-negligible issue. In this paper, the lightning attachment characteristic of a 2-MW wind turbine generator (WTG) is investigated using a model with a reduced scale of 100. The WTG model is equipped with receptors on the blades and a lightning rod on the nacelle, both serving as its external lightning protection system (LPS). The high-voltage electrode, which delivers a lightning impulse voltage from a Marx generator, is used to simulate the final stage of downward negative lightning strikes from 29 coming-leader positions. The experimental results indicate that lightning leaders from either front directions or side directions could be intercepted effectively by LPS, whereas the back-direction lightning could not. Moreover, with the increase of striking distance, the capture ratio for the insulation part of blade decreases. Electric field intensity distribution simulations for the full-scale WTG model, using conditions similar to their experimental counterparts, are conducted and compared with the lightning attachment distribution. Based on classical electro-geometrical model, a simulative method is proposed to predict the lightning attachment distribution of WTG. Our results indicate that it is feasible with this method to produce a satisfactory approximation to the experimentally obtained lightning attachment distribution.