电晕笼中分裂导线交流电晕损失计算分析

电晕损失是导线电晕特性研究的重要内容之一,但针对交流导线电晕损失的计算模型的研究较少,为此在建立电晕笼内导线电晕损失计算模型中应用了模拟电荷法,采用线电荷模拟交流导线,对正方型截面笼壁分别作镜像处理;计算导线表面电场强度不均匀性对电晕放电的影响时考虑了空间电荷的因素;导线模拟电荷量超过起晕电荷量条件下分别计算导线上每个...     

特高压电晕笼的多分裂导线电晕损失测量系统

为准确、连续地测量特高压分裂导线电晕损失,对传统的电桥法进行改进并根据特高压电晕笼机械与电气特性,结合光纤传输技术,采用混合型光供电电子式电流互感器测量特高压电晕笼中分裂导线电流;采用电容分压器测量特高压电晕笼导线试验电压。基于虚拟仪器技术,采用瞬时功率法研制了一套光纤数字化特高压电晕笼电晕损失测量系统,经校验该系统满足0.2级准确度要求,能够较为准确测量电晕笼导线电晕损失。对晋东南-南阳-荆门特高压交流试验示范工程用8×LGJ-500/35导线开展起始电晕特性和电晕损失特性试验研究结果表明,在干燥条件下分裂导线起晕场强为27.64 kV/cm(峰值),正常运行电压下不会出现全线起晕的情况;20 mm/h大雨条件下分别对应特高压交流单回试验线段边相和中相导线表面场强,电晕笼导线电晕损失为50.83 W/m和59.73 W/m;可以应用该系统进一步研究我国特高压交流输电线路电晕损失规律。     

特高压电晕笼直流分裂导线正极性电晕起始特性分析

为了研究特高压电晕笼分裂导线正极性电晕起始特性,应用模拟电荷法计算绞线的表面电场,采用一次镜像,最外层的每一股铝线用8个模拟电荷代替,依据极不均匀电场下电晕自持判据以及光电子二次发射过程,计算特高压电晕笼绞线的起始电压。应用特高压电晕笼进行了单根钢芯铝绞线(LGJ)900-75导线,6*LGJ900-75(分裂间距450),8*LGJ400-35(分裂间距400)导线干燥和降雨率分别为2.4mm/h,20mm/h,30mm/h条件下的电晕损失试验研究。通过切线法得到了三种形式导线干燥情况下的起晕电压,计算和试验起晕电压的对比分析说明计算模型可以应用于计算特高压电晕笼直流导线正极性的起晕电压,在此基础上进一步的分析计算表明:特高压电晕笼导线正极性电晕起始电压随着分裂数的增加而增加,随着分裂间距的增加而降低,随着子导线半径的增大而增大;淋雨条件下的表面粗糙度,随着降雨率的增加而降低,同时呈现出饱和的趋势。     

不同海拔下电晕笼分裂导线起晕电压的计算分析

为了研究海拔高度对电晕笼分裂导线起始电晕电压特性的影响,建立电晕笼钢芯铝绞线起始电晕电压的计算模型,并开展相应试验研究。采用模拟电荷法计算钢芯铝绞线的空间电场强度。依据极不均匀电场下自持放电判据,建立不同海拔高度电晕笼分裂导线电晕起始电压的计算模型。在超/特高压人工环境气候试验室内,以500 m海拔高度为间隔,系统开展19~4-000-m海拔高度范围内六分裂导线起始电晕电压的试验研究。试验获得超高压电晕笼不同海拔高度下6-LGJ—400/50、6-LGJ—500/45分裂导线的起晕电压。计算获得不同海拔高度、分裂间距、导线分裂数及绞线表面粗糙系数下的导线起晕电压曲线族,以及不同绞线半径及最外层铝绞线股数的表面粗糙系数计算结果。分析结果表明:计算模型能够较好地计算电晕笼内绞线的起晕电压;在350~500-mm分裂间距范围内,分裂导线起晕电压随着分裂间距的增大而降低,随着导线分裂数的增加而升高;绞线表面粗糙系数与绞线最外层铝线半径与绞线半径之比相关。     

在小电晕笼中分裂导线交流电晕的起始电压分析

电晕起始电压是研究导线电晕特性的重要参量,对于指导超、特高压输电线路的设计具有重要意义。为此,利用电晕笼进行电晕起始电压的研究,电晕笼尺寸为1.8 m×1.8 m,测量段部分长3 m,两侧防护段各有0.5 m长。实验时,将导线同轴放置在电晕笼的中心位置,利用电晕笼电晕损失测量系统测量不同电压下导线的电晕电流和电晕损失,根据电压-电晕损失曲线,利用切线法估算导线的电晕起始电压值,并研究在导线表面干净和污秽条件下不同导线的电晕起始电压值,获得了LGJ-300/40、LGJ-400/35和LGJ-630/45导线在干净和污秽条件下的起晕特性。研究结果表明,干净条件下,起晕电压随导线半径增加而下降,污秽条件下导线起晕电压变化规律类似。此外,随污秽尺寸增大,对导线表面场强的畸变作用增强,这也会降低导线起晕电压。     

基于有限元分析的500 kV分裂导线电晕研究

分裂导线的使用不仅可以提高线路的输电能力,也能减小电晕。从分裂导线的分裂数、导线半径和等效半径三个参数入手,定量计算三者对减小电晕的作用,经过模型的建立与改进,仿真结果表明:三个参数中分裂数对导线附近的最大电场强度影响最大,对电晕损耗的影响也最大;导线半径与最大电场强度之间没有特殊的规律,利用该模型计算备选导线表面最大电场强度,可以为分析比较哪种导线最合适提供理论依据;对于固定的分裂数和导线半径,存在一个最佳等效半径,能使得导线表面电场强度最低,电晕损耗最少。     

采用电晕笼的交流分裂导线起晕电压海拔修正系数分析

电晕笼是用来模拟输电线路导线电晕特性的一种经济、有效的方法。为了深入研究海拔0～3800m范围内交流输电线路电晕起始电压的海拔修正系数,利用可移动式小型电晕笼在武汉、西宁、格尔木、纳赤台进行了多种4分裂导线的电晕特性试验。导线电晕放电后产生了光子,紫外成像仪可以记录光子的数量,从而利用切线法求取导线的电晕起始电压。通过武汉、西宁、格尔木和纳赤台4个不同海拔点的导线在干燥条件下的电晕起始电压测量结果,发现它们不适合用GB/T2317.2-2000或GB/T775.2-2003来进行海拔校正,因而提出了工程用指数和线性海拔校正方法,误差5%,可以满足工程实际需要。     

电晕笼内导线交流电晕起始电压判断方法

导线电晕引起的电磁环境问题是特高压输电线路建设的技术难题之一.电晕起始电压是反映导线电晕特性的重要参数,而当前对电晕起始电压的判断方法并不统一.电晕笼是一种用来模拟实际输电线路电磁环境的经济、有效的工具,为得到比较准确的判断方法,通过在小型电晕笼中,对单根实际输电导线进行电晕实验,同时利用紫外成像仪、局部放电仪、无线电...     

导线雷电冲击电晕特性试验研究

雷电侵入波的特性对变电站内设备的绝缘裕度设计有较大的影响,而目前中国进行变电站设备雷电绝缘裕度设计中,忽略了输电线路的电晕会引起雷电侵入波衰减畸变,导致设计结果通常较为保守,因此有必要对雷电冲击电晕进行系统研究。在中国特高压交流试验基地开展了冲击电晕试验,对输电线路中常用的导线进行了雷电冲击电晕试验研究,总结了不同导线的雷电冲击电晕伏库特性曲线。试验结果表明:在雷电冲击下导线起晕较为明显,不同导线的伏库特性曲线表现出一定的规律性,且在正极性雷电冲击下导线表现出明显的起晕延时现象。基于试验结果可建立相应的线路冲击电晕模型,应用于电磁暂态软件中仿真计算线路冲击电晕对线路雷电侵入波的影响。     

Effect of conductor geometry on bundle conductor galloping

A computer simulation of an elastic catenary was used to study the wake-induced galloping of a two-conductor bundle transmission line. It was shown that increasing the conductor separation reduces the region of galloping instability and decreases the amplitude of the resulting galloping. Stranded conductors are more likely to gallop at low wind speeds while smooth conductors gallop at high wind speeds. Since the fundamental frequency depends on span length, span has a large effect on galloping, with shorter spans being more susceptible. Twisting of the bundle one-half turn per span essentially eliminates galloping.     

Finite-element solution of monopolar corona on bundle conductors

A finite-element iterative-based method is developed to analyze the monopolar ionized field and, hence, compute the associated corona power loss on bundle conductors (bundles two, three, and four are considered). The effect of the number of bundles, and the bundle spacing on the corona current and ground-plane current density profiles is investigated. It has been found that, with the increase in the number of bundles, the corona current decreases. On the other hand, the corona current increases with the increase in the bundle spacing. A laboratory model was built to check the accuracy of the calculated corona current and the ground-plane current density profiles. It has been found that the present results agreed well with the present and previous experimental values     

220kV架空分裂导线的应力动态分析

为了更好地评估过电流对水平排列导线伸长、导线间距的影响,研究了导线间距与电磁力相互作用的机理.通过建立输电线路为抛物线模型,利用模型计算导线电磁力、导线长度、导线拉应力,并分析计算拉应力、电流等因素对分裂子导线导线伸长、间距的影响.继而利用数值计算软件求出不同状态下子导线最小间距,并分析不同电流对导线间最小距离的影响,综合以上分析,建立过电流下导线伸长动态模型.基于以上分析可知:各种因素对导线伸长和最小间距存在影响,伸长与电磁力相互促进;动态模型显示导线伸长过程中各种参数变化,与导线粘连临界状态参数进行比较以判定导线粘连,并提出相应预防粘连的措施.     

An investigation of microstrip conductor loss

Microstrip conductor loss exhibits complicated behavior that is not generally recognized. Specifically, there are three frequency ranges of interest. At low frequency, current is uniform through the entire cross-section of the line, and the line behaves like a resistor. At medium frequency, the edge singularity forms. In this case, current concentrates on the edge of the line, increasing the resistance. At high frequency, the current splits into two sheets of current, one on top of the line, the other on the bottom of the line. Since microstrip dispersion causes the edge singularity to become larger and current to concentrate on the bottom side as frequency increases, the total resistance increases faster than the normally expected square root of frequency     

Corona loss characteristics of contaminated conductors in fair weather

In the present work, the results of a laboratory measurement project of corona losses on contaminated conductors in fair weather are presented. The measurements carried out furnish new information, which is not available in the literature. The research work performed in the past has dealt with corona losses under rain and snow, and some semiempirical formulae have been proposed, which do not approach adequately the corona losses in the case of contamination in fair weather. A calculation formula for the case of contaminated conductors in fair weather has been proposed in this work on the basis of the performed research, and the corresponding fitting coefficients have been calculated. An appropriate mathematical tool for the predetermination of corona losses is hence available for this case.     

Impedance of a rectangular conductor of the starting cage of a double-cage motor

Contents The impedance of a rectangular conductor of the starting cage of a double-cage motor is calculated by using the Babnow-Galerkin method. The working cage is assumed to consist of cylindrical conductors. Graphs of the resistance and inner reactance are given.

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Die Impedanz eines Leiters mit rechteckigem Querschnitt im Anlaufkäfig eines Doppelkäfigläufer-Motors

Übersicht Die Impedanz eines Leiters mit rechteckförmigem Querschnitt im Anlaufkäfig wird mit Hilfe der Bubnow-Galerkin-Methode berechnet. Dabei wird angenommen, daß der Arbeitskäfig zylindrische Leiter aufweist. Es werden Diagramme des Widerstandes und der inneren Reaktanz angegeben.

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List of Main Symbols A z-component of the vector potential (complex r.m.s. value) - B _x ,B _y components of the magnetic induction (complex r.m.s. values) - h length of slot between conductors - I, I _J ,I ₂ currents (complex r.m.s. values) - imaginary unit - r ₁ radius of conductor - R ₁,R ₂ resistances - R _1.0,R _2.0 ohmic resistances - X ₁,X ₂ reactances - Z,Z ₁,Z ₂ impedances - z ^* conjugate complex number ofz - Rez, Imz, |z| real part, imaginary part and modulus of complex numberz - /n derivative in the normal external direction - ² scalar Laplacian - half of the angle corresponding to slot width - permeability - conductivity - pulsation - _n Kronecker symbol     

Corona characteristics of distribution line in contact with conductive material and life estimation of conductor insulation

In relation to accidents due to bird nests in contact with overhead distribution lines, the authors investigated the life estimation of conductor insulation. Accidents are often caused by crows or magpies. There is a region in which magpies have been designated a protected bird in Japan. In that region, the nests cannot be easily removed in the breeding season. Recently, metal wires have been used as nest material. When this conductive material is in contact with a distribution line and arm, a corona discharge will occur. The conductor insulation of the distribution line suffers deterioration and there is a possibility of causing an accident. In this study, an acceleration test was performed to investigate the time from nest building to an accident in the distribution line. The acceleration factor based on the charge amount of the corona and the influence of the applied voltage on corona characteristics was discussed. The life of the conductor insulation was discussed in terms of the V–t characteristics and the acceleration factor. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(4): 25–32, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21260     

特高压输电线路分裂导线表面电位梯度的计算及其特性分析

通过对工程中计算导线表面电位梯度的常用数学模型进行准确度校验,提出逐步镜像法由于具有较高的计算精确度,而且最大误差远小于可以接受的工程误差限值,适合我国在进行特高压输电线路设计和电磁环境研究时使用。基于逐步镜像法,计算了1000kV交流单回和同塔双回输电线路的导线表面电位梯度,重点分析了线路对地高度、导线分裂根数、子导线半径、导线布置形式和双回路相序布置方式等因素对特高压线路分裂导线表面电位梯度取值特性的影响。     

Inception voltage of corona in bipolar ionized fields-effect oncorona power loss

In this paper, an iterative finite-element-based algorithm is presented as a numerical tool for the solution of the bipolar ionized field around high-voltage DC (HVDC) transmission lines. The effect of including unequal values of the positive and negative corona inception voltages and ion mobilities on the corona power loss is investigated. In addition, the effect of negative ion field enhancement on reducing the positive conductor corona inception voltage is also studied. The present algorithm is applied to different laboratory and full-scale transmission line configurations. Comparison with previously computed V-I characteristics showed that the present computed values were in better agreement with the experiment. Also, it has been found that the effect of unequal corona inception voltages on the corona power loss (or corona current) is noticeable at applied voltages very near to the inception values     

Corona power loss determination on multi-phase power transmission lines

This paper presents a method to calculate the corona power loss and the ground-level electric field values for three- and six-phase power transmission lines. The charge simulation technique is applied in which the surface charge on the stressed conductors as well as the space charge around each conductor are represented by two discrete sets of unknown infinite line charges. Satisfying properly chosen boundary conditions at the transmission-line conductor surfaces results in a system of linear algebraic equations whose solution evaluates the unknown line charges. The emission of ions from a conductor surface is assumed to take place when the magnitude of the charge simulating its surface charge exceeds an onset value based on a pre-defined corona onset field value for both positive and negative half cycles. The simulation space line charges are displaced back and forth to the conductor by the action of the electric field whose magnitude and direction depend on the simulation charges in the conductor and in the surrounding space. Recombination process takes place whenever charges of opposite polarities meet together. The calculated corona power loss for three-phase power transmission lines agreed satisfactorily with those reported earlier, and for the first time, the six-phase corona power loss will be presented.