A practical method for evaluation of ground fault currentdistribution on double circuit parallel lines

The paper presents an original analytical procedure for quick and, for practical purposes sufficiently accurate evaluation of the principal components of the ground fault current. The procedure is valid for faults at any of the towers of a double 3-phase circuit line with an arbitrary number of spans. The method is obtained by application of relatively simple and exact equations for uniform ladder circuits of any size (for any number of pis, from one to infinity) and for any terminal conditions. The method can be applied to solve several practical problems: the evaluation of the maximum substation grounding system fault current, the selection of a ground wire capable of withstanding the fault currents and the prediction of step and touch voltages near the transmission towers. In the case of a double circuit 3-phase line, the solution of these problems is additionally complicated by the mutual inductive coupling between the two parallel lines     

OPGW架空输电系统任一点接地短路电流分布的研究

架空输电线路发生接地短路时,短路电流在光纤复合架空地线(OPGW)上的分布对电力系统有重要影响。传统计算OPGW线上短路电流的方法大多采用工程简化计算和基于序分量法的计算,并且只考虑接地短路发生在杆塔处的情形,计算结果过于粗糙。为此提出了基于相分量模型对全线任一点接地短路电流计算的方法。分别提出接地短路发生在杆塔处和杆塔间不同的数学模型,进一步求解相导线和OPGW每一级档距上的电流。数值算例验证了在杆塔处接地短路分流模型的正确性,杆塔处接地短路的分流结果进一步验证了杆塔间接地短路分流模型的正确性,并在实际工程中进行了应用。对于复杂的OPGW架空输电系统,基于相分量模型的计算方法能够准确计算全线任一点发生接地短路时,OPGW线上短路电流的分布情况。     

基于磁场测量的配电网单相接地选线及定位新方法

输电线路发生接地故障时,架空线下方磁场能反映线路故障信息。输电线路短路电流大小不同,线路下方磁场相应地不同,即输电线路下方磁场的变化能够完全反映线路中电流的变化,磁场可以应用到电力系统保护中。配电网多为单端电源供电方式,针对配电网的复杂性及传统定位方法精度不高提出了一种基于磁场的非接触式故障选线及定位的新方法。利用磁阻传感器非接触测量杆塔下方磁场,根据磁场的幅值和相位选出故障线路,确定故障点位置。磁阻传感器测量精度高,成本低,故障距离可以确定在两个杆塔之间。利用MATLAB建立线路模型,仿真验证了理论的可行性。     

Analysis of ground fault current distribution along nonuniform multi-section lines

In case of a substation supplied by a combined overhead-cable line, most of the ground fault current flows through the cable sheaths and discharges into the soil surrounding the point of discontinuity, where cables are connected to the overhead line. In the paper a new method is presented for computing the ground fault current distribution in case of feeding line consisting of two or more different sections, i.e. part overhead and part underground cable. Besides the calculation of the earth current at the fault location, the leakage current at the transit/transition stations as well as at the overhead line towers can be evaluated, in order to ensure proper safety conditions. Based on the two-port theory, the method allows to take into account all the relevant conductively and inductively coupled parameters which take part to the fault current distribution. A computer program based on the proposed method has been developed and some application examples are reported.     

基于电磁暂态程序的架空地线分流系数的计算

为了准确计算变电站接地网接地短路电流和架空地线的分流系数,以某500 kV输电系统为例,采用电磁暂态程序(the alternative transient program-electormagnetic transient program,ATP/EMTP)对系统中各主要元件进行建模,计算变电站内、外发生单相接地故障时短路电流的分布和架空地线的分流系数,分析变电站接地网接地电阻、杆塔接地电阻、地线型号、线路长度、变电站外短路位置等对其接地短路电流和地线分流系数的影响,得出接地网电阻、杆塔接地电阻增大,出线回路数减少时,接地短路电流增大,架空地线的分流系数减小的结论。     

500 kV输电线路绝缘地线雷电流分布

对于重覆冰区域的输电线路来说,地线覆冰会严重威胁到线路的安全运行。采用绝缘地线直流融冰的方式是解决架空地线覆冰问题的方法之一。当输电线路发生雷击事故时,直流融冰采用的绝缘地线与杆塔之间的雷电流分布情况决定了杆塔的塔顶电位,影响着杆塔的耐雷水平与线路防雷接地的保护。利用电磁暂态软件EMTP,对杆塔和绝缘地线中的雷电流分布进行了计算分析。计算结果表明,在500 kV输电线路中,雷电流主要通过杆塔流入大地,雷电流的幅值、杆塔档距、接地电阻的大小、地线结构、直径以及地线接地方式等对绝缘地线和杆塔分流情况有重要的影响。计算结果可为绝缘地线分流系数和杆塔分流系数的研究提供重要的参考价值,并有利于指导输电线路的优化设计。     

New fault location system for power transmission lines usingcomposite fiber-optic overhead ground wire (OPGW)

A fault location (FL) method using composite fiber-optic overhead ground wires (OPGWs) was developed to find out where electrical faults occur on overhead power transmission lines. This method locates the fault section by detecting the current induced in the ground wire, i.e. the OPGW in this system. Since detected fault information is essentially uncertain, the fault information is treated in the proposed FL method as a current distribution pattern throughout the power line, and fuzzy theory is applied to realize the manner of fault location used by electrical power engineers. It was confirmed by computer simulations that the fault section can be accurately located using this method under various conditions. This FL system was applied to several commercial power transmission lines and successfully located the sections where electrical faults occurred     

Estimation of shielding failure number of transmission lines for different trace configurations using leader progression analysis

The electrogeometric model (EGM) is a technique used for analyzing the termination of lightning flashes on transmission lines and masts, etc. When using the EGM for modeling the lightning stroke to transmission lines, the power line has normally been represented by a set of horizontal wire and both the sag of the wire, the existence of the towers and effect of uneven way have been ignored. This approach has serious short comings including inability to determine the percentage of the strokes terminating on the towers, failure to correctly predict the effect of height, and giving an approximate value for the number of collected strokes. This paper presents the development of a method for estimating the shielding failure number of power transmission lines in different trace configurations by using the charge simulation method. The effects of towers, sags of conductors, and a perfectly conducting ground are represented in 3-D computation. In addition, the stepwise descending nature of a downward negative leader–streamer systems taken into account by using an appropriate progression model. Upward leader inception and propagation is also modeled utilizing critical equivalent streamer-length criterion. The method is applied to compute the shielding failure of power transmission line for different trace configurations. In this paper the 3-D method is extended by modeling the effect of sloppy trace, trees on both and one side of the transmission line with extensive simulation results. Also, in this paper the effect of variation of tree height, its distance from transmission line and the number of trees on SFN are analyzed and results are shown in curves.     

Efficient reduction of fault current through the grounding grid ofsubstation supplied by cable line

The paper presents an analytical procedure suitable for the determination of the part of the ground fault current emanating from the substation grounding grid in the conditions when a particular measure has been taken to reduce it. The practical realization of this measure can be simply described as burying one bare copper wire of a certain length in the same trench as the cable feeding line. In the case of an overhead feeding line, the similar measure is denoted in the expert literature as the “counterpoise”. The presented method enables a quick and, for practical purposes, sufficiently accurate evaluation of the copper wire length providing the maximum possible reduction of the substation grid current. The conveniences of the method result from the simplicity of the formulae for the determination of the realized grid current reduction at the effective copper wire length     

超特高压同塔4回输电线路工频电场强度的计算

通过对输电线路适当等效建模,应用模拟电荷法在输电线内部设置模拟线电荷,计算了超特高压同塔4回线路的导线表面电场强度和距地面1.5m处的工频电场强度,并与目前的特高压双回鼓型塔、单回猫头塔、单回酒杯塔和单回紧凑塔进行比较。结果表明,同塔4回线路的导线表面电场强度不高于其他塔型,同时地面工频电场强度要明显小于其他塔型。其理论依据为同塔的500kV导线屏蔽了1 000kV导线在地面方向的大部分电场。     

考虑电容电流的同塔双回线接地距离保护零序电流补偿系数的整定

分析了同塔双回线路在独立运行方式下零序互感和电容电流2种因素对零序电流补偿系数的影响.推导了接地距离保护的数学模型,在传统接地距离保护基础上,提出一种零序电流补偿系数整定新方法,即零序电流补偿系数为原始零序电流补偿系数、附加零序互感补偿系数与附加电容电流补偿系数之和,给出了零序电流补偿系数计算公式. PSCAD仿真结果表明,整定范围为线路80%时,线路末端故障情况下,所提方法比传统方法更能准确地反映故障位置,且能使两侧的距离 I 段保护范围有交叉,提高了同塔双回线路的距离保护性能     

Single‐phase to ground fault current distribution in transmission system based on the improved double‐side elimination method

In order to calculate the fault current distribution when a single‐phase to ground fault occurs in a transmission system with asymmetric parameters, this paper proposes an improvement on the traditional double‐side elimination method based on the phase component model. The improved double‐elimination method widens the range of the original method to the situation of multiple overhead ground wires and double power sources at both terminals. From the fault point, it divides the system into the left and right networks. Taking the left network as an example, the equations of all spans are formed. Then, the forward–backward recursive process of the theory is demonstrated. By optimizing the matrix calculation process, the calculation model for computers is formed, which can easily calculate the fault current on phase wires and overhead ground wires when a single‐phase to ground fault occurs. By comparing the results from this theory and the results from the EMTP simulation software, the correctness of the theory is established. Furthermore, in this paper we give a detailed discussion on the influence of tower grounding resistance and overhead ground wire operation mode on the fault current distribution. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

变电站内短路情况下架空地线分流系数的图论计算方法

架空地线分流系数是确定变电站接地电阻目标值的基础数据,提出了基于图论的多电源供电变电站站内接地短路时架空地线分流系数的计算方法。通过分析变电站内短路时影响架空地线分流的因素,给出了电路模型,用基于图论方法的戴维宁、诺顿等效原理和节点电压法推导出了计算架空地线分流系数的公式。与引用的一个算例进行了数据对比,证明了等值电路模型计算方法的正确性。通过计算实例反映出了架空地线分流系数随故障变电站内接地电阻的增大而增大,随线路杆塔接地电阻的增大而减小,线路前15基左右的架空地线–杆塔系统对架空地线分流系数起决定性影响。     

基于热稳定计算的架空地线分析研究

从地线热稳定角度出发,针对输电线路发生单相接地短路故障,先计算两根架空地线返回的总电流,再确定每根地线分配的电流,最后校核地线热稳定。结合220kV张家坝变至秀山变线路工程实际,通过对地线组合OPGW与铝包钢绞线进行热稳定校核分析,为输电线路架空地线选型、校核提供参考。     

同塔双回直流输电线路的感应电压仿真研究

随着对输电能力需求的扩大,同塔双回输电技术不仅在交流输电领域应用广泛,而且在直流输电领域也逐渐得到了应用。针对同塔双回直流输电线路之间电磁耦合带来的感应电压问题,采用雷电流仿真模型、杆塔多波阻抗模型和绝缘子先导闪络模型。并建立雷电绕击故障计算模型和接地故障计算模型,对不同运行电压、导线排列方式、土壤电阻率以及排列间距等对同塔双回直流输电线路感应电压的影响进行分析,以溪洛渡直流工程为参考．研究在不同运行方式、输送功率以及加装线路避雷器情况下,同塔双回线路间的电磁耦合特性。在对溪洛渡工程实例采用ATP—EMTP进行仿真的基础上,分别对雷电绕击和接地故障2种情形下的感应电压进行计算。比较并得出了影响线路间感应电压的主要因素。     

架空线路短路电流分布及地线屏蔽系数的计算

采用相分量法计算了架空线路中短路电流的分布和地线屏蔽系数。计算结果表明,当架空线路发生对地短路故障时,如果考虑架空地线的回流作用,那么电力线路对附近通信线路的感性耦合的影响源（相导线与地线电流之和）在短路点和电源之间呈倒Ｖ型分布,其特点是在短路点和电源处的电流较小而线路中间区域电流较大。架空地线的实际作用或回流系数远大于依据中国电力部颁布的《送电线路对曜线路危险影响设计规程》所计算的结果。     

基于参数识别的时域法双端故障测距原理

提出了一种基于参数识别的时域法双端故障测距原理。无需已知被测线路的准确参数,而将输电线路电阻、电感、电容等参数作为待识别参数,分别由线路两端电气量采样值计算沿线的电压分布,利用故障时只有故障点处电压相等的基本原理识别出准确的线路参数并计算出故障点位置, 克服了传统测距方法因线路参数不准确而引起的测距误差。该测距方法采用故障距离占线路全长的比例表示故障定位结果,该结果不受季节、弧垂等变化的影响,便于利用杆塔的地面距离估测出故障点位置。ATP仿真结果表明该方法具有较高的测距精度。     

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     

直流接地极对附近输电线路杆塔的腐蚀影响及防护措施的研究

直流电流在大地中流散时,大地将呈现一定的电位分布,当直流接地极址靠近输电走廊时,将有直流通过地线在处于不同等电位面的杆塔之间流动,从而造成杆塔接地体及基础导体的腐蚀.笔者针对锦屏—苏南±800 kV特高压直流输电工程送端龙恩接地极址,以距极址最近的二自Ⅱ回500 kV交流线路为例,将直流接地极、土壤结构、避雷线和杆塔接...     

Method for calculating the ground resistance of grounding grids using FEM

Taking as given that ground resistance is independent of earth fault current, this paper presents a new way of calculating ground resistance of grounding grids using the finite-element method (FEM). Ground resistance is calculated by means of three consecutive tests, with an acceptable number of elements, and fast resolution. The results of the proposed method are compared with those measured experimentally or determined by other authors. Once ground resistance and earth fault current are known, grid potential and touch-and-step voltages are calculated. The main advantage of the method proposed here is that it permits us to analyze symmetrical and nonsymmetrical grids of any shape in uniform, two-layer, and multilayer soils. The method developed in this paper constitutes a fast-resolution industrial application, with acceptable results, for calculating the ground resistance of grounding grids of any shape.