Countermeasures for controlling lightning‐caused overvoltage on indoor wiring with communication line

Overvoltage generated by lightning is a threat to indoor electrical equipment in our information‐oriented and computerized society. Countermeasures for preventing overvoltage on indoor wiring are demanded. Therefore, we have investigated the effectiveness of some countermeasures, such as low‐voltage arresters, communication line arresters, SPDs, and a common grounding wire, for reducing the overvoltage on indoor wiring with a communication line. In particular, we have studied the effect of the combination of these countermeasures and their layout on controlling the overvoltage, using a full‐scale test distribution line with a customer's facility. The main results are as follows:

• (1) A common grounding wire installed along the low‐voltage indoor wiring is more effective for reducing the overvoltage on the indoor wiring with a communication line than is one installed under the floor, when the arresters are installed at the panel board.
• (2) Combination of an SPD and other countermeasures, such as low‐voltage arresters and a common grounding wire, is effective for controlling the overvoltage on the indoor wiring, and the effectiveness of these countermeasures for preventing damage of electrical equipment has been verified by an experiment using actual electrical equipment. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 37–45, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10223

     

A distribution line model for lightning overvoltage studies

Recently, the focus of lightning protection measures for distribution lines has moved from a nearby lightning stroke to a direct lightning stroke. Studies of direct lightning stroke countermeasures are generally carried out by digital simulations using the EMTP (Electro‐Magnetic Transients Program). Thus, components of a distribution line must be modeled appropriately in the EMTP for accurate simulations. The authors have previously clarified the surge response of a distribution line by pulse tests using a reduced‐scale distribution line model. In this paper, first, the results of the pulse tests are simulated in the EMTP using a conventional model which represents a distribution pole by a single lossless distributed‐parameter line model, and comparisons with the test results show that transient overvoltages generated at the insulators cannot accurately be reproduced by the conventional model. This indicates that a special treatment is required to represent the transient response of a distribution pole and wires. Then, this paper proposes new EMTP models of the pole and wires which can reproduce the transient overvoltages at the insulators. The parameter values of the proposed models can be determined based on a pulse test result. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 11–23, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.21001     

Equivalent Circuit of Distribution Line for Lightning‐Induced Voltage Analysis Using Analytical Formulas

This paper proposes an equivalent circuit at a transition point of distribution line for lightning‐induced voltage analysis. The lightning‐induced voltages caused by a piecewise linearly varying lightning current are expressed by analytical formulas. The equivalent circuit is represented by resistors and current sources, which are known from past history and given by the lightning‐induced voltage on an infinite‐length line. Transient voltages and currents at the transition point are accurately obtained in small computation time using the equivalent circuit. Thus, the proposed equivalent circuit is very convenient for analyzing the lightning‐induced effect in complicated electric power networks. This paper presents an example of EMTP data cards to use the proposed equivalent circuit in the EMTP.     

A modeling method and EMTP simulations of an inverter surge

A numerical simulation of the inverter surge is carried out using a frequency‐dependent model of a cabtyre cable. The frequency‐dependent model is based on the Semlyen line model in the EMTP, for which the required parameters are determined from the measured results of the wave propagation characteristic in the cable. A simple model of an induction motor is proposed considering resonances in the motor. The simulated result by the EMTP agrees reasonably well with the measured result. The proposed model can be useful for predicting the peak voltages observed at the motor terminal of inverter‐operated motors. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

浪涌保护器的应用分析

针对建筑物和电子信息系统的雷电灾害防护现状,对雷电的特性、浪涌保护器（SPD）的分类和功能作了简要的介绍,详细阐述了电源线路SPD和信号线路SPD在实际防雷工程中的选用。最后对SPD的后备防护作了简要的介绍,以供设计人员参考。     

Mechanism of pole‐mounted transformer damage by backflow lightning and measures against the damage on low‐voltage distribution line

Pole‐mounted transformers are especially vulnerable to lightning damage. The progress of the information society imposes increasingly stringent requirements for the reliability of electric power supply, and this in turn necessitates a reduction in lightning damage to pole‐mounted transformers. Lightning protective devices (surge arresters) are now being installed around the primary bushing of the transformers, which has decreased the number of disconnections around the primary bushing due to lightning. But surge arresters installed on the primary side of the transformer cannot protect it against backflow lightning entering the secondary side of the transformer. The characteristic of transformer damage by backflow lightning is that the electromagnetic force produced by the current flowing into the secondary side deforms the transformer windings. This paper elucidates the mechanism of transformer damage by lightning flowing into the secondary side by comparing actual lightning damage cases with the results of verification tests using a short‐circuit generator. Effective countermeasures against transformer damage by backflow lightning are examined by EMTP calculations, which indicate that neutral grounding on the low‐voltage distribution line is the most effective way of decreasing the current flowing into the transformer. The lower the grounding resistance, the less current flows into the transformer. In addition, decreasing the voltage on the secondary side is important in order to protect the secondary‐side bushing. The calculation results indicate that surge arresters installed around the secondary side of the transformer are effective in decreasing the voltage on the secondary side. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 1–11, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20921     

某螺旋钢管厂综合防雷改造

根据2005—2010年沧州雷电定位数据,分析了沧州地区雷电分布规律和螺旋钢管厂雷击事故的原因,从接地装置、低压配电系统、计算机系统、视频监控系统和大型电器设备等几个方面提出了综合雷电防护措施,提高了厂区的雷电防护水平。     

稳态计算中2种EMTP线路模型的比较研究

对2种常用的EMTP线路模型进行了比较,分析了常规π形电路和固定参数线路模型的计算误差,提出了一种计算方法验证这些模型的准确性.结果表明进行工频稳态模拟时,在适当长度下,常规形电路模型是相当准确的.然而,目前有相当多的EMTP使用者仍习惯采用周定参数模型进行不换位线路的稳态计算,在这种模型中,复数的、频率相关的转换矩阵被简化为实常数矩阵;特殊情况下,采用固定参数模型会引起相当大的计算误差,该问题应引起足够的重视.     

输电线路杆塔分流系数仿真计算

利用CDEGS软件针对220 kV/500 kV典型输电线路杆塔分别进行工频和雷电流模型的仿真计算,给出避雷线、杆塔地网、杆塔基础具体分流大小,分析影响杆塔分流系数的影响因素。     

Effective lightning protection schemes for distribution line

The causes of lightning outage are subdivided into direct lightning strokes and induced lightning strokes, which are identified by the characteristics of the lightning overvoltage. In the past, lightning protection devices were directed mainly toward the latter, and attention has been focused on the installation of lightning protection devices, ground wires, and reinforcement of insulators. However, lightning outages continue to occur. Thus it is extremely important to clarify the fault characteristics of lightning surges and to study the effectiveness of various lightning protection devices by considering both direct lightning stroke and induced lightning stroke in order to prevent lightning outage in the future. In this research, the electromagnetic transients program (EMTP) has been applied to the direct lightning stroke, and the induced lightning outage analysis program for multiple conductor systems has been applied to the induced lightning stroke to study the effectiveness of lightning protection devices provided by combination of various lightning protection devices. The most effective lightning protection schemes are analyzed and evaluated based on verification tests on the full scale models as well as economic considerations.     

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     

基于磁环的输电线路雷击过电压抑制方法

提出一种基于磁环抑制的方法对输电线路进行雷击防护。首先采用曲线拟合得到磁环材料的磁化函数,进而基于微元法与电磁场理论计算建立了磁环的磁链计算模型,并利用有限元法(FEM)验证磁链计算模型的合理性;然后,利用磁环的磁链计算模型在ATP/EMTP中建立磁环电磁暂态模型,进而分析了不同磁环材料、磁环截面积、磁环长度及磁环形状对磁环抑制雷击过电压效果的影响。基于典型的110 kV输电线路对所提方法进行仿真。结果表明：磁环磁链计算模型与FEM计算结果最大误差低于5 %,验证了所提方法的合理性;增加磁环的截面积和长度能加强磁环的雷击过电压抑制效果,但在外半径、长度分别取60 mm、6 m后出现了饱和现象。现场试验结果表明,安装磁环后,雷击过电压得到了有效的降低,仿真和试验结果之间的最大误差为5.92%,验证了所提磁环磁链计算模型、电磁暂态模型的正确性以及磁环抑制雷击过电压方法的可行性。     

A field study of lightning overvoltages in low‐voltage distribution lines

The number of home electric appliances, such as personal computers and telephones, has been rapidly increasing. Lightning damage to these home electric appliances has a great impact on a highly sophisticated information society. There are cases in which lightning overvoltages in low‐voltage distribution lines cause malfunctions in them, even though they are equipped with surge protective devices to protect against lightning overvoltages. Therefore, for lightning protection of low‐voltage equipment including home electric appliances, it is important to understand the phenomenon of lightning overvoltages in low‐voltage power distribution lines. However, many aspects of this problem are not entirely clear, in particular how they are generated. The Tokyo Electric Power Company carried out lightning observations on low‐voltage distribution lines. The observation results provide a statistical distribution of lightning overvoltages in low‐voltage distribution lines. A mechanism for generating lightning overvoltages in low‐voltage distribution lines is inferred from the observed waveforms and facilities data. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 12–21, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21299     

电涌保护器应用中几个问题的探讨

探讨了电涌保护器（SPD）应用中的4个颇有争议的问题，这就是SPD的响应时间、多级SPD的动作顺序、不同波形中冲击电流的等效变换以及SPD的残压与冲击电流峰值的关系。最后说明了SPD应用中各电压之间的相互关系。     

Surge analysis of the tank of a gas-insulated line using lumped constant circuits

Surge voltages evaluated by a digital analysis method, for example, electromagnetic transients program (EMTP) and by an analog analysis method (transient network analyzer: TNA) are compared with experimental results on a scaled model of a gas insulated line. From the results, it is confirmed that the analog analysis method has a satisfactory accuracy and its computing speed is quite high. The error caused by the lumped element modeling of the gas insulated line is comparatively small, and the line is not necessary to be treated as a distributed parameter line. The lumped element model is advantageous to understand the mechanism of the transient characteristic of the induced transient voltage. A simple equivalent circuit of the gas insulated line is proposed and its accuracy is confirmed by a comparison with the calculated result obtained by an accurate line method. The transient overvoltages of the tank and across the insulated flange can be analytically calculated using the equivalent model.     

火电厂仪控设备防雷击电磁脉冲的措施

介绍了上海地区几座电厂仪控设备遭雷击受损的分析,遵循经济、实用,高标准、严要求,高起点、安全可靠的原则,参考和引入IEC的有关防雷击标准要求,提出了相应的防范措施。     

建筑物防雷保护设计浅谈

在感应雷的防护当中,电涌保护器能根据各种线路中出现的过电压、过电流及时做出反应,泄放线路的过电流。在建筑物内根据不同的防雷区设置不同的电涌保护器,可以有效遏止直击雷和感应雷入侵建筑物内的电气设备,从而达到保护电气设备的目的。     

井冈山革命博物馆新馆的防雷与接地设计

阐述了井冈山革命博物馆新馆建筑物防雷等级和电子信息系统防雷的计算分析,以及所采取的防雷措施。讨论了在女儿墙顶暗敷防雷带的依据。并对利用独立基础内主钢筋构成接地网和在高电阻率地区降低接地电阻的措施进行了介绍。     

TT系统雷电流分布的研究

对雷电流、雷电防护系统、配电变压器等进行建模,利用EMTP研究了单相、三相TT系统遭受雷击时雷电流在系统中的分布。并且研究了雷击系统的不同位置、不同的雷电流波形、供电系统的线路阻抗对雷电流的分布影响。研究表明,接地电阻的改变对雷电流的分布影响较大。     

防雷竣工检测步骤中的常见问题

结合防雷装置检测的实践,阐述了雷电灾害防护装置的竣工检测步骤。根据相关标准和工作经验,对竣工检测中一些常见问题作了总结,并提出了相应的解决建议,为雷电灾害防护及检测工作者提供参考。