Experimental and analytical studies on lightning surge characteristics of a buried bare wire

Lightning surge analysis is very important from the viewpoint of insulation design of transmission lines and substations. Lightning surge analysis has many parameters, which include lightning surge characteristics of transmission towers, back flashover phenomena at an arcing horn, characteristics of footing resistance, effects of corona wave deformation, characteristics of electromagnetic fields caused by lightning, and other parameters. This paper describes experimental and analytical studies on lightning surge characteristics of a buried bare wire. The measurement of the lightning surge characteristics of the buried bare wire is carried out under various experimental conditions. The experimental parameters controlled in these experiments include earth resistance, length of the buried bare wire, and waveform of the injected current. The measured results are compared with analytical results based on the theoretical study by Sunde. A comparison of the measured results with the analytical results shows good agreement. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(3): 35– 41, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20532     

Effect of lightning overvoltages on low-voltage power distribution lines due to direct lightning hits to overhead ground wire

Overhead ground wires and surge arresters have been installed to protect high-voltage power distribution lines and apparatus from overvoltages induced by nearby lightning strokes. The effects of surge arresters for protection of high-voltage distribution lines against direct lightning strokes have already been investigated using the digital simulation program EMTP (Electromagnetic Transients Program). With regard to the protection of low-voltage distribution lines from overvoltages induced by lightning strokes, experimental analyses using a scale model line have been reported. This paper reports on the comparison between the experimental analyses and EMTP simulation of power distribution lines, including low-voltage lines, and the validity of EMTP simulation. Furthermore, this paper analyzes the overvoltages on low-voltage power distribution lines against direct lightning strokes to overhead ground wire using the digital simulation.     

雷电侵害DCS的途径及防范措施

2004年夏天，上海地区有4个火电厂因雷击造成DCS部分I／O摸块和外围压力，温度变进器等损坏及部分温度参数突变。引起热控设备损坏的原因有电源及信号电缆接地不良、虚接地及利用安装支架作为接地等情况。从雷电对控制设备损害情况分析，由感应雷引起的事故约占雷害事故的80％-9％。雷电对DCS的危害主要是通过直击雷和雷电电磁脉冲的冲击干扰．造成对电子设备的直接损坏。DCS防雷手段主要有防雷接地和防雷保护器，而良好的接地及尽量减小接地电阻是有效防雷的基础条件。电力行业对DCS接地电阻的要求是：采用独立接地时接地电阻应小于4Ω；采用与电气网共地时接地电阻应小于1Ω；采用防雷地、电气地、DCS地三者共地时应小于0．5Ω。     

Analysis of lightning surge propagation in wind farm

Wind power generation is expected to become more important in future distribution systems. Although several prospective reports such as IEC 61400‐24 and NREL SR‐500‐31115 indicate an insulation scheme and grounding design for lighting protection, there still seems to be too few investigations on the problems. This paper therefore discusses lightning surge analysis using a wind farm model with 2 or 10 ideal wind turbines. Changing parameters such as grounding resistance and lightning strike points, several cases were studied. As a result of the analysis using digital simulator ARENE, it is clear that the surge tends to propagate toward the end of a distribution line in a wind farm and there is the possibility of insulation accidents at the other wind turbines when lightning attacks a wind turbine. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(2): 30– 38, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20364     

再析避雷针(线)防直击雷作用

从影响避雷针（线）保护范围主要因素及其无法定量等方面说明了世界各国的避雷针（线）保护范围计算方法均是经验公式,并就GB 50057—1994选用外国经验公式提出质疑;同时指出避雷针（线）保护范围的绕击率除应经理论、实验室分析研究外还要靠实践运行统计分析得出,并分析了实际工程中不宜设置较高的独立避雷针（线）,非金属结构屋顶应用避雷网,不宜用避雷针的原因。     

雷击建筑物时的雷电流分布研究

建立了雷电流、雷电防护系统、配电变压器等配电网络的模型，利用国际通用的电磁暂态分析程序EMTP研究了TT系统（一种典型的低压与电系统）在遭受雷击时，雷电流在TT系统中的分布。并研究了单相和三相供电、不同波形的雷电流、传输线的线路阻抗对雷电流分布的影响。     

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。     

Results of lightning impulse tests for a 275‐kV full GIS substation

This paper describes the outline and results of the lightning impulse tests for a 275‐kV full GIS substation. The behavior of lightning surges is a very important factor for the rational design of substations and low‐voltage and control circuits inside the substations. For the above reason, we carried out lightning impulse tests for a new 275‐kV full GIS substation. In these tests, we measured voltage induced in low‐voltage and control circuits, transient characteristics of grounding grid, injected voltage and current waveforms, and so on. By investigating these data, we confirmed the behavior of lightning surges inside the substation. We also compared simulated waveforms by EMTP analysis with the measured waveforms. The simulated results agreed well with the measured results. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 46–58, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10230     

An impedance measurement of a small‐capacitance circuit using transient responses for lightning surge analysis

A method to measure a small capacitance with its loss resistance using a set of transient current waveforms is proposed in this paper. The parameters are obtained from the time constants in the time domain. The method has high resistance to extraneous noise, because a time‐to‐frequency transformation, which is sensitive to noise, is not required. The transient current waveforms are obtained by a voltage or current source, a current transformer, and a waveform recorder. The measured capacitance by the proposed method is not affected by the capacitance of the voltage probe, because it is obtained without any voltage information. The sheath surge impedance of the current injection cable, which is indispensable for the transient measurement, is corrected. The application of the method has the advantage in that it allows the modeling of a fast transient of a power apparatus, comparing it with the steady‐state measurement using an impedance measuring instrument. The proposed method is applied to create an equivalent circuit between electrodes implanted into a piece of wood, and its reliability is confirmed by comparison between the measured and calculated results. Stray capacitances of a miniature circuit breaker are also measured, and the results show that the proposed method is applicable to equipment in power systems. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

输电线路雷害分析及防雷措施

基于对黄冈电网220kV及以上输电线路历年雷击闪络故障的分析,以及找到的故障原因,提出了降低杆塔接地电阻、加装线路避雷器和安装可控放电避雷针等多种防雷措施,并进行了实施,经过实际运行验证,采取的这些防雷措施有效地降低了线路雷击跳闸率。     

Numerical electromagnetic analysis on current distribution in building directly hit by lightning

Lightning current distribution in a directly hit building is studied by using a simple equivalent circuit and an electromagnetic model. The Numerical Electromagnetics Code (NEC‐4) is employed for numerical electromagnetic analysis. The error in the shunt ratio of lightning current entering wiring, which is calculated using the electromagnetic model, is estimated to be less than 4%. The shunt ratios for lightning current entering the wiring on the top floor and the first floor are largest. Although they are larger for a higher building, they are almost constant if the building struck has more than five floors. They are smaller when there are more vertical conductors, or the length of the wiring is longer. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 9–16, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20449     

Analysis of one-line ground fault surge on simulated overhead distribution line

One-line fault location techniques of intermittent ground fault points on nongrounded distribution lines are necessary to supply steady electric power for customers. This paper proposes a novel method that uses frequency spectra of transient waveforms at a sending end when an intermittent ground fault occurs. In this method, if a ground fault position differs, it causes a different frequency spectrum pattern for the current or voltage transients at a send end (decided by surge reflection phenomena between the sending end and the ground fault point). Comparison between experimental data of one-line ground fault tests on a simulated overhead line (373 m line length, two branch points) and digital simulation analyses shows that the grounded capacitance of a power source transformer was useful in locating the ground fault point. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (1): 52–60, 1997     

高压输电线路采用深层垂直接地体的探讨

从降低杆塔接地电阻方面进行探讨,提出应用层垂直接地体来提高输电线路耐雷水平的设想。它是利用深层潮湿土壤的土壤电阻率较低来降低杆塔的接地电阻的,并且有不易受外力破坏、不易氧化锈蚀、钢材消耗量小等优点,广东省中山电风２２０ＫＶ横小线的部分杆塔采用了深层接地形式,测量和统计数据表明,深层接地能降低杆塔接地电阻和线路雷击跳闸率。     

500 kV变电站运行方式及工频相角对雷电侵入波过电压的影响

雷电侵入波过电压是对500kV变电站电气设备绝缘构成威胁的主要方式之一.选取典型500kV变电站,分析了杆塔与绝缘子的计算模型,并应用ATPDraw仿真软件计算500kV变电站运行方式与工频电压相角对雷电侵入渡过电压的影响.     

别把避雷针(线)保护范围"绝对化"

分析了避雷针(线)的防雷保护原理和影响避雷针(线)保护范围的主要因素,认为：1)当今国内外所有避雷针(线)防雷保护范围的计算公式都是经验公式,这是因为影响着避雷针(线)防雷效应的主要因素无法定量;2)所谓避雷针(线)保护范围是相对于被保护物在此空间内遭受雷击的概率而言的,各种文献规定的保护范围不同,是因允许遭受雷击概率不同;3)不能把避雷针(线)保护范围“绝对化”。     

浙江电网雷电定位系统落雷密度图分级应用的研究

分析了浙江电网各地区2004~2006年线路雷击跳闸次数与落雷密度的相关性、3年间多次雷击跳闸的线路雷击故障点与落雷密度分布的相关性,从而发现高落雷密度区域线路雷击跳闸率高于低落雷密度区域的特点,据此提出了落雷密度图分级应用的初步设想。     

一次人工引雷雷电流和地电位升高监测

根据2006年夏季在山东滨州地区的一次火箭引雷试验观测中雷电流和地电位升高的资料．对雷电作用于伸长接地体上引起的地电位升高和接地电阻特性进行分析。从波形可以看出,雷电过程中有两次回击,一次峰值为4159kA,时间参数为602/2024μs,另一次峰值为2959kA,时间参数为48/11μs。以往对接地体的冲击特性研究都是限于试验室中的标准波形,此次试验反映出真实雷电过程中接地体的接地电阻变化特性。同时采用ATP仿真法计算出水平接地体在雷电流下的冲击援她电阻,与实际情况进行比较。结果显示,仿真计算结果不随雷电流波形参数发生变化。雷电流和地电位升高波形峰值存在时间差,仿真中不能体现这一特点。     

500 kV变电站接地网设计用以控制电磁干扰问题的研究

现代电力工业生产,特别是高压及超高压变电站存在和应用大量电气、电子设备,形成了错综复杂的电磁环境。如何制定针对性较强的措施,达到电磁兼容是现代电气设计施工必须解决的课题。在探讨变电站电磁兼容问题时,接地装置是不可忽视的一个重要方面。接地装置的设计施工及运行情况的好坏不仅影响电力系统安全运行,也是影响变电站电磁干扰的重要方面。以成都电业局500kV龙王变电站为例,分析了变电站电磁干扰特性和传播形式。在提出了一般性的控制措施的基础上,重点通过500kV变电站接地技术设计来改善和控制变电站的电磁干扰问题。     

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。     

Suppressing the effect of lightning-induced overvoltages by the combined use of surge arresters and overhead ground wires

Lightning voltage induced by nearby strokes is one of the causes of major overvoltages which threaten the insulation of power distribution lines. Surge arresters as well as an overhead ground wire usually are employed for the protection of equipment and line insulation on overhead power distribution lines. The fundamental mechanism of suppressing effects of overvoltages induced by nearby strokes has been demonstrated independently by one of the present authors for surge arresters and for an overhead ground wire. In this paper, the protective effect of the combination of surge arresters and overhead ground wire is analyzed. As a result, it is found that the effect of surge arresters used together with an overhead ground wire is almost the same as that of surge arresters alone.