Lightning-induced voltages on multiconductor overhead lines

The effects of other conductors in a multiconductor overhead line on the voltages induced on a conductor by a nearby lightning strike are analyzed on the basis of previous studies on long single-conductor overhead lines. It is shown that the presence of other conductors affects the induced voltage of a conductor, particularly for vertically configured lines; however, the amount is less than that originally predicted. Ground wires reduce the magnitude of the induced voltages, thus acting as partial shields. The amount that the ground wires reduce the induced voltages on the conductors is dependent on the position of the ground wires in relation to the ungrounded conductors     

Role of an overhead ground wire in the generation of lightning-induced voltage over lossy ground

The role of an overhead ground wire on the generation for lightning-induced voltage on a multiconductor line associated with a vertical return-stroke channel is studied based on numerical calculation. The induced voltage is calculated by a method in which the tangential component of the electric field to the wire is looked upon as an inducing source. The analyzed multiconductor line consists of three phase wires and an overhead ground wire having one or two earthing points. The influence of the overhead ground wire on the induced voltage is dependent on the direction of a return stroke, as well as the ground conductivity. When a return stroke is on the side of a power distribution line, the induced voltage decreases with a decrease in the earthing resistance of the overhead ground wire, irrespective of the ground conductivity. When a return stroke is close to an end of a distribution line, the influence of the overhead ground wire is dependent on the ground conductivity. In this case, the voltage induced on overhead wires over lossy ground sometimes increases with the presence of an overhead ground wire having only one earthing point. This effect can be avoided by adding earthing points to the overhead ground wire. © 1998 Scripta Technica. Electr Eng Jpn, 121(4): 18–27, 1997     

Determination of thermal softening of overhead wire exposed to an electric arc effect

Systems of overhead current transfer are the main mechanism for power supply of electric rolling stock. Noncontinuous interaction of the bow collector with the overhead wire (with, from time to time, the bow collector skid detaching from the overhead wire) results in spark and electric arc formation. The most dangerous effect is the influence of an electric arc on the limited amount of overhead wire material, during which the wire heats up to very high temperatures: copper annealing (recrystallization) occurs, and soft (annealed) copper is formed. This copper has a different internal structure, which leads to poorer mechanical performance of the material. This article describes a method of determining the softening degree of overhead wire exposed to electric arc effect. The method is based on the suggested evaluation criteria. A case of calculations is given for particular conditions of the bow collector interaction with the overhead catenary. The method makes it possible to determine the degree of overhead wire softening.     

光纤复合电线标准化和系列化探讨

论述了光纤复合电线标准化和系列化的必要性、可行性，探讨了列入型谱的准则和构想，提出了制定产品系列型谱的建议。     

光纤复合架空地线机械计算的探讨

从理论上阐述了光纤复合架空地线在大气过电压情况下,如何满足规程规定的导地线距离的要求。介绍了光纤复合架空地线的架线形式,提出了实际工程中按耐张型悬挂方式的光纤复合架空地线应力的求解方法,并对弧垂观测档的选取进行了探讨。通过此方法计算在大气过电压情况下的弧垂曲线,能满足工程需要。     

架空地线的融冰方法及改进措施

对覆冰的架空地线常采取短路融冰的措施,这种操作复杂或者难以实现,针对重点覆冰路段采用专门的融冰变压器进行融冰,既操作简单,又容易实现.     

高压架空线路计算机自动化设计

在高压架空送电线路设计过程中,导线的应力、铁塔的受力以及基础的作用力等计算十分繁琐。利用计算机高级语言程序来代替人工对设计项目进行数据管理、力学计算和出图,这个过程称之为高压架空送电线路计算机自动化设计(以下简称OTLCAD)。1实现OTLCAD的可行性同其他人工智能一样,OTLCAD除基于硬件外,还依赖于建立合理的数学模型并程序化。自动化设计要求从数据的采集(主要是全站仪线路测量或GPS测量、地质勘探等)、传输、运算到成果输出整个过程的智能化。个人计算机和电子测量仪器的飞速发展使其广泛应用成为可能。电子测量技术的…     

Fearing electricity: overhead wire panic in New York City

Many historians have portrayed the late nineteenth century as a period of great technological utopianism or enthusiasm. Closely intertwined with this technological enthusiasm, however, was also a strong strand of technological pessimism. Americans of this period desired innovations like electric lighting and communication, rapid transit, and gas cooking and heating, but they also feared the physical hazards created by these innovations. They believed that new technology would improve society, but at the same time worried that they had no control over the pace and direction of this change. An early example of the technological pessimism of this period was the electric wire panic that took place in New York City in the 1880s. At this time, the streets of the city were darkened by dangerous, overhead electric wires. The failure of the city to bury these wires, along with debate over electrical safety, generated great fear of electricity. This fear reached its height in 1889 when a series of horrible electrical accidents terrorized the city. Despite their fears, most New Yorkers found it impossible to give up electrical technology. The tension between technological enthusiasm and pessimism created a profound anxiety about electricity and the new urban world it was creating     

架空导线压接对边距的图像测量方法

压接导线主要应用于架空线路建设,其对边距对线路安全运行及服役期限起到重要作用。针对传统人工测量存在的可靠性差、效率低的缺点,提出了一种基于图像处理的压接对边距测量方法。首先根据图像的累计灰度突变点自动裁剪被测区域并进行中值滤波,然后基于改进Otsu阈值法获得边缘连续的二值图像;再分别使用形态学处理和高斯曲线拟合法对边缘进行二次定位,得到亚像素级边缘点;最后采用基于随机抽样一致性（random sample consensus,RANSAC）的最小二乘拟合方法完成上下边缘点的曲线拟合,实现压接对边距的测量。通过模拟试验表明了RANSAC拟合经过10次迭代后测量算法的效果较好,测量误差小于0.1 pixels;而实际导线测量试验结果表明,改进Otsu算法对光照强度具有适应性,同时与人工测量相比,图像测量方法的最大相对偏差为1.82%,重复标准差提高60%,平均耗时仅为人工测量的1/10,能够实现压接对边距高效可靠的测量。     

基于CSO-SVR的低压架空线路谐波损耗评估

针对低压架空线路物理解析模型谐波损耗计算精度不高的问题,文中提出采用基于纵横交叉优化(CSO)算法的支持向量回归(SVR)模型对架空线路谐波损耗进行评估。首先,采用结构风险最小化设计的SVR模型,拟合线路特征与谐波损耗之间的关系。然后,利用CSO算法对SVR超参数进行全局搜索,以动态优化获取最优超参数组,建立CSO-SVR谐波损耗评估模型。文中依托国内某大型电能质量综合试验平台进行低压架空线路谐波试验,获得线路谐波损耗实测数据,并基于该数据对所提模型进行验证。结果表明,采用CSO算法对SVR超参数进行优化,可有效提升SVR模型的谐波损耗评估性能。与其他模型相比,所提模型的评估精度更高。     

低压配电网零线电压分布的研究

我国低压电网用电采用380V／220V三相四线制供电系统。由于零线不与地线直接相连,为了保护用户,防止发生触电事故,通常还需要单设一条地线将用电设备接地。但是很多地方的楼宇住宅没有地线或者地线接地不是很好,在使用电器设备时就存在着一定的安全隐患。在三相负荷对称的情况下,零线与大地电位相等,但是当三相负荷不对称时,零线的电位将出现偏移。本文通过理论分析和Matlab／Simulink软件仿真计算了零线上的电压分布情况,计算结果表明零线上的偏移电压不会超过36V,不会对人体造成危害。在电器设备的设计中虽然零线不能代替地线的使用,但可以用零线当作地线的备用,对低压电器设备的安全运行起到辅助作用。     

光纤复合架空地线(OPGW)的试制

本文综述了光纤复合架空地线 (OPGW)的各结构元件设计、总体设计及工艺控制等诸环节的技术要点 ,提出了 OPGW的优点 ,并列出了 OPGW所涉及的特性参数计算公式及说明。     

Evaluation of medium voltage enameled wire exposed to fast repetitive voltage pulses

The paper describes the investigation of the failure mechanisms of medium voltage inter-turn insulation, as a consequence of pulse aging. To study the performance and failure behaviour of enameled wires, models of inter-turn insulation are prepared with enameled wires having polyimide and nano-filled coatings. The aging of such bar samples is attained by sinusoidal (60Hz), fast repetitive unipolar voltage pulses, and high frequency AC waveforms. To establish the residual strength of the bar samples, DC breakdown voltages are determined before and after the aging. In addition, the thermally stimulated depolarization current (TSDC) is used to provide information about the relaxation processes, such as the disorientation of the dipoles and the release of charges from the trapping sites in enameled wires. The various trapping levels, which have discrete energy differences with distinct peaks in the thermograms, are discussed in terms of space charge polarization     

220 kV直线杆塔架空地线提升器的改进

1现状分析用于220 kV输电线路直线杆塔架空地线横担的原架空地线提升器的底面与架空地线横担接触面积很小,而且提升器是单边丝杠,两边受力不平衡,使用中很容易出现打滑、跑偏等现象。另外,原架空地线提升器安全系数低,一定程度上威胁着安全生产。原提升器详见图1所示。图1原220     

分流系数对架空避雷线热稳定校验的影响

针对北京电网中日益突出的架空避雷线热稳定问题,指出了目前根据线路总短路电流值选取架空避雷线截面是不准确的。通过建立数学模型,采用Matlab软件进行计算,得出分流系数对避雷线截面选择有着明显影响,并通过实例计算加以证明。进行的分析和计算为更准确地进行架空避雷线的热稳定校验提供了理论依据,同时还给出了考虑分流系数后GJ50架空避雷线的适用距离,可供工程技术人员参考。     

Reliable power supply tapped from the overhead ground wire on 735 kV transmission lines

The presence of electrical energy in the overhead ground wire on transmission lines has been known for many years. Its possible utilization in remote areas offers many advantages but unfortunately, owing to technological problems, access to this source was very difficult. Hydro-Quebec, as a utility interested in this energy source, asked its Research Institute to carry out studies of the possible applications. Very encouraging results have been obtained and this paper describes the various solutions examined with a view to making use of such available power at low cost, together with the solution adopted for building an operational 20 kW prototype; this prototype was developed for the microwave repeaters of the James Bay project.     

Numerical algorithm for medium voltage overhead lines protection and adaptive autoreclosure

In this paper a new numerical algorithm for medium voltage overhead line protection and autoreclosure is presented. It is based on one terminal data processing and it is derived in the time domain. In the algorithm, the fault location and fault nature (arcing or arcless fault) are estimated using the linear least error squares estimation technique. An arc occurring on the fault point during arcing faults on overhead lines is included in the consideration of the problem. Additionally, by introducing the pre-fault load current in the existing model, better algorithm performances are achieved. The algorithm is derived for the case of a three-phase symmetrical fault. The computer simulation results of the algorithm testing are presented and, in particular, the algorithm sensitivity to arc elongation effects and processing of the signals in the presence of harmonics is tested and analysed.     

Lightning protection of medium voltage overhead lines by modular long-flashover arresters

A long flashover arrester (LFA), which comprises three flashover modules using the creeping discharge effect, is described in this paper. In this design, the total arrester-stressing voltage is applied simultaneously to all of the modules so that the voltage-time characteristics of the arrester are improved considerably assuring reliable protection of medium voltage (e.g. 10 kV) overhead power lines against both induced overvoltages and direct lightning strokes. A single LFA per support or pole is found to be sufficient to protect an overhead line against induced overvoltages. An LFA should be arranged in parallel with each insulator in order to protect a line against direct lightning strokes.     

电压波动与闪变对架空线路损耗影响分析

为探讨架空线路在电压波动与闪变影响下的损耗,利用短线路模型,定性分析了架空线路各项损耗,在电压波动与闪变的国标规定范围内,设定波动幅值及波动频率步长,进行实验仿真,仿真结果表明：架空线路附加损耗与频率波动的一次方呈正相关,与幅值波动的一次方及三次方呈负相关比例,与幅值波动的二次方呈正相关比例,且正比于频率波动与幅值波动的乘积。最后给出了通过最小二乘多项式拟合技术计算线路损耗的方法,并运用Simulink模型验证其有效性。