A Novel Fault Location Algorithmfor Double-Circuit Transmission Lines based on Distributed Parameter

Anewfault location algorithmfor double-circuit transmissionlines is described inthis paper.Theproposed method uses data extractedfromtwo ends of the transmissionlines andthus eliminates the effects ofthe source impedance andthe fault resistance.The distributed parameter model and the modal transformationare also employed.Depending on modal transformation,the coupled equations of the lines are converted intodecoupled ones.Inthis way,the mutual coupling effects between adjacent circuits of the lines are eliminatedandtherefore an accurate fault location can be achieved.The proposed methodis tested via digital simulationusing EMTP in conjunction with MATLAB.The test results corroborate the high accuracy of the proposedmethod.

Extraction of distributed parameters for multi-conductor transmission lines by the difference iteration method

The distributed parameters of the transmission lines have the significant impact to the signal propagation. In the conventional method of the distributed parameter extraction,the discontinuity of inverse trigonometric or hyperbolic can arise the problem about phase ambiguity which causes significant errors for transmission models. A difference iteration method（ DIM） is proposed for extracting distributed parameters of high frequency transmission line structure in order to overcome the phase ambiguity in the conventional method（ CM）. The formulations of the proposed method are first derived for two-conductor and multi-conductor lines. Then the validation is performed for the models of micro-strip transmission line. Numerical results demonstrate that the proposed DIM can solve the problem about the phase ambiguity and the extracted distributed parameters are accurate and efficient for a wide range of the frequencies of interest and line lengths.

Stability Analysis of Multi-paralleled Grid-connected Inverters Including Distribution Parameter Characteristics of Transmission Lines

The sparse distribution characteristics of renewable energy resources can lead to there being tens of kilometers of transmission lines between a grid-connected inverter and the actual grid.Accurate analysis of the stability of such gridconnected inverter systems currently involves using a complex hyperbolic function to shaped model of the transmission line circuit.This has proved to be problematic,so,drawing upon the distribution parameter characteristics of transmission lines,this paper looks at how to use impedance-based stability criteria to assess the stability of multi-paralleled grid-connected inverters.First,the topology of multi-paralleled inverters connected to the grid via transmission lines is established,using each transmission line terminal as a grid connection point.Each grid-connected system is taken to be equivalent to a small-signal circuit model of the“current source-grid”.Euler’s formula and the Nyquist stability criterion are combined to assess the stability of the associated grid-connected current transfer functions and evaluate the stability of the grid-connected current.Finally,a simulation analysis circuit is constructed to verify whether power line intervention will cause stability problems in the grid-connected system.Overall,it is found that long-distance transmission lines are more likely to cause unstable output of the grid-connected current.It is also found that the number of grid-connected inverters,the short-circuit ratio(SCR),the distorted grid and the inverter parameters can all have a significant impact on the stability of the grid-connected current.

强风作用下输电塔线体系连续性倒塌分析

为分析强风作用下输电塔线体系连续性倒塌的过程,将已发生破坏的输电塔作为薄弱塔,采用等效位移的方式考虑薄弱塔倒塌对挂线点空间位置的影响,计算相邻输电塔(目标塔)在薄弱塔多组倒塌特征变量组合工况下的响应和破坏特征,确定对目标塔具有最大影响的薄弱塔倒塌特征变量.结果表明:在发生连续性倒塌时,目标塔的破坏包括近薄弱塔侧的塔身破坏和塔头破坏2种形式;目标塔近薄弱塔侧背风面主材应力比最高,斜材应力比一直较低;塔身下部斜材失稳与主材应力的持续增大是目标塔整体倒塌的最直接原因;薄弱塔的倒塌过程持续时间是目标塔是否破坏的主要控制变量.

考虑气象参数预测误差条件分布的架空输电线路载流量概率预测方法

准确考虑气象参数预测误差是实现架空输电线路动态载流量精准预测的基本前提。通过统计与计算分析,首次发现在不同气象参数预测值与气象环境下,气象参数预测误差具有不同分布特征。然而,现有架空输电线路载流量概率预测方法并未考虑以上2种因素的影响,难以实现线路载流量的准确预测。为此,首先将气象参数预测误差分析问题构建为气象参数预测值与气象环境2种影响因素下的气象参数预测误差条件分布求解问题;其次引入Sklar定理及其Copula函数和非参数核密度估计法,构建了一种气象参数预测误差条件分布的求解方法;然后结合蒙特卡洛采样法,提出了一种考虑气象参数预测误差条件分布的架空输电线路载流量概率预测新方法。最后通过计算分析发现:相比于2种传统方法,所提方法在考虑气象参数预测值与气象环境2种因素对气象参数预测误差概率分布的影响后,预测区间覆盖率分别提高了5.51、1.99个百分点,预测区间标准化平均宽度分别降低了7.86、3.62个百分点,验证了该方法的准确性与实用性。

One high-efficiency analysis method for high-speed circuit networks containing distributed parameter elements

In the field of high-speed circuits, the analysis of mixed circuit networks containing both distributed parameter elements and lumped parameter elements becomes ever important. This paper presents a new method for analyzing mixed circuit networks. It adds transmission line end currents to the circuit variables of the classical modified nodal approach and can be applied directly to the mixed circuit networks. We also introduce a frequency-domain technique without requiring decoupling for multiconductor transmission lines. The two methods are combined together to efficiently analyze high-speed circuit networks containing uniform,nonuniform,and frequency-dependent transmission lines. Numerical experiment is presented and the results are compared with that computed by PSPICE.

基于多维参量分布式光纤传感的架空输电线路覆冰监测技术

对比总结了典型DOFS技术的基本原理与系统结构,对现有输电线路覆冰监测技术发展现状进行介绍。在此基础上提出了一种多维参量分布式光纤传感技术,能够实现对线路的应变、温度、振动、衰耗等状态参数进行分布式的实时监测。与现有的单参量、双参量传感监测方案相比,使用多维参量方案对线路进行融合感知,可以有效提高监测的准确度,降低误判率、误报率,为输电线路的安全稳定运行提供重要保障。

Equivalent electromagnetic parameters for microwave metamaterial absorber using a new symmetry model

Transmission line theory uses the complex nature of permeability and permittivity of a conventional magnetic absorber to evaluate its absorption properties and mechanism. However, because there is no method to obtain the electromagnetic parameters of a metamaterial-absorber integrated layer(composed of a medium layer and a periodic metal array), this theory is seldom used to study the absorption properties of the metamaterial absorber. We propose a symmetry model to achieve an equivalent complex permittivity and permeability model for the integrated layer, which can be combined with the transmission line theory to calculate metamaterial absorption properties. The calculation results derived from both the transmission line theory and the high-frequency structure simulator are in good agreement. This method will be beneficial in practical investigations of the absorption mechanism of a metamaterial absorber.

Using Universal Line Model (ULM) for Representing Three-phase Lines

The second-order differential equations that describe the transmission line are difficult to solve due to the mutual coupling among phases and the fact that the parameters are distributed along their length. A method for the analysis of polyphase systems is the technique that decouples their phases. Thus, a system that has n phases coupled can be represented by n decoupled single-phase systems which are mathematically identical to the original system. Once obtained the n-phase circuit, it’s possible to calculate the voltages and currents at any point on the line using computational methods. The Universal Line Model (ULM) transforms the differential equations in the time domain to algebraic equations in the frequency domain, solve them and obtain the solution in the frequency domain using the inverse Laplace transform. This work will analyze the method of modal decomposition in a three-phase transmission line for the calculation of voltages and currents of the line during the energizing process.

同塔双回输电线路相参数新测量计算方法

输电线路相参数是线路过电压计算的基本参数,获取同塔双回交流线路的相参数对于指导工程运行是必要的。为准确获得同塔双回交流输电线路的相参数,建立微分形式的输电线路方程,对微分方程用拉普拉斯变换与反变换进行推导,获得输电线路相参数与各相导线首、末端电压和电流关系的测量用数学模型。在不同方式下,多次同步测量各相导线首、末端电压和电流,将所测数据代入模型求解参数。经仿真验证,对100~500km的线路最大偏差为1.47%,可适用于任意长度同塔双回线路,是一种新的相参数测量获取方法,满足电力系统过电压计算对参数准确性的需要。

适用于输电线路暂态分析的频率相关模型

为提高电力系统电磁暂态计算精度,输电线路元件模拟常用分布参数,电磁暂态仿真软件中,也有与之匹配的输电线路频率相关模型。为验证ATP与PSCAD中该模型的精确度,提出一种时域仿真反推算输电线路衰减系数的方法,通过卡尔松公式计算输电线路理论衰减系数;分别建立输电线路电磁暂态仿真模型,使系统在某一频率下进行暂态仿真直至稳态,分析线路中点与末端电压波形,利用稳态参数反推算其衰减系数,比较在不同频率下与理论计算所得衰减系数的误差;通过对比输电线路参数理论计算值与仿真计算值,分析误差产生的原因。结果表明:输电线路暂态过程中,高频下的衰减系数远大于工频。随着频率的升高,输电线路参数正序、零序的衰减系数都逐渐增大,且零序表现的更为明显,在频率为50000 Hz时,其衰减系数可达到工频时的17倍;比较理论与仿真计算结果,ATP中的频率相关模型参数计算比较精确,50000 Hz时计算出衰减系数误差为0.66%,PSCAD中衰减系数误差较为明显,50000 Hz时计算出衰减系数误差为3.41%,且随着频率的增大,衰减系数误差也越来越大。究其原因,PSCAD中线路参数计算得到的电阻值偏大,其与程序中求解频变参数计算公式有关,电磁暂态仿真时需予以重视。

基于特勒根拟功率定理的直流输电线路故障测距

高压直流输电系统的网络结构和故障特性对线路故障测距方案准确度提出更高要求,对此,该文提出一种基于特勒根拟功率定理的直流输电线路故障测距方案。首先,在分析直流线路贝瑞隆模型的基础上,首次提出特勒根拟功率定理应用于直流线路故障分析的方案,并给出拟功率解析表达式。其次利用贝瑞隆模型构建拟功率基准值,并根据故障点处基准值与计算值相等的原则实现故障测距。最后,通过大量仿真,验证理论推导的正确性以及拟功率能有效反应故障位置,并验证该方案不受过渡电阻及故障类型的影响。该研究实现了低采样频率下高精度测距的目标。

基于空充暂态电流的线路保护CT极性校验方法

线路保护电流互感器(current transformer, CT)二次采样回路接线正确是保护正确动作的前提。针对线路投运启动过程中保护CT极性校验困难的问题,首先分析了在有限负荷和无负荷下利用线路稳态电流进行极性校验的边界限制条件。进而针对不满足限制条件下无负荷极性校验困难的问题,提出了一种基于空充暂态电流的线路保护CT极性校验方法。该方法先利用幅值较大的本端暂态电流对三相CT相对极性进行初判,再通过线路本端暂态电流和测量电压基于线路结构计算对端暂态电流来实现本端保护CT极性错误相识别,CT极性正确时对端计算电流理论上为零,CT极性错误时会呈现较大的幅值。该方法有效解决了传统极性校验方法在负荷不足时无法校验的问题。仿真和录波验证了该方法的有效性,并已纳入工程应用方案。

机载线缆间的串扰耦合分析

串扰是机载设备间互联线缆干扰耦合的重要因素。以混合模S参数为基础,建立单线-双绞线模型以模拟机载设备之间的动力线缆对信号线产生的串扰耦合。在此模型基础上提出串扰耦合测试方案,搭建串扰耦合测试系统,并根据测试获得的耦合系数评估单线-双绞线线间串扰耦合强弱。通过测试比较,对影响因素进行分析,结果表明,距地高度对线间串扰影响不大,线间距对线间串扰耦合影响显著,因此在条件允许下尽可能增加设备间互联线缆的间距可有效抑制串扰耦合。

基于分布参数的直流线路谐波电流放大特性

针对双极高压直流线路中存在的谐波电流放大问题,在分析线路分布参数的基础上,提出了一种直流线路谐波电流传递系数的定量计算方法,可用于评估谐波电流的放大水平。首先,从多导体线路的耦合关系及双极线路结构出发,建立了架空线路的谐波阻抗模型;其次,推导了线路谐波电流传递的解析式,并据此深入分析了谐波传递放大的主要影响因素;然后,基于均匀传输线的波过程,揭示了谐波电流的传递规律;最后,结合某直流输电工程的技术参数,在采用非均匀线路送电的三端运行方式下,在PSCAD仿真平台中验证了所提出的线路谐波电流计算方法的准确性。

基于分布参数模型的混合输电线路精确测距及重合闸方案的研究

华东镇海-舟山500 kV线路工程采用复杂的电缆-架空线混合输电线路,发生故障时无法准确对故障位置进行定位,且现有的重合闸方案无法实现自动识别架空线路故障并投入重合闸。文章提出一种基于分布参数模型的混合线路故障测距方案。该方案采用正序故障分量,利用混合线路各段准确参数,分别采用线路两侧电气量计算沿线各点的电压有效值。根据两侧电气量计算的故障位置电压有效值相等的特点,对故障位置进行准确计算。且针对实际工程对重合闸的需求,提出一种故障位置区段定位方法。该方法通过比较用两侧电气量计算的电缆和架空线交界处电压有效值,对故障所在区段进行定位,以实现故障点位于电缆线路时不重合闸,故障点在架空线时重合闸。仿真结果表明,采用华东镇海-舟山500 kV线路工程各段准确参数,各故障位置、各故障类型测距误差均不大于2.5%或±1 km,测距结果不受过渡电阻影响,且可实现自动识别架空线故障并投入重合闸。

高压输电线路宽频散射响应高效求解方法

针对传统均匀采样模型参数估计(MBPE)技术求解高压输电线路宽频散射特性存在的精度低、可靠性差等问题,引入一种自适应能力强的新MBPE技术,与构建的自适应频率采样算法结合,提出了一种准确快速求解高压输电线路宽频散射特性的新方法。以IEEE中波广播研究频段和调幅广播收音台工作频段为例,分别建立高压输电线路散射场的直线与线-面混合模型,将矩量法、MBPE技术和自适应频率采样算法结合,确定自适应采样点散射场信息和Stoer-Bulirsch有理插值函数,实现高压输电线路散射场宽频响应预测。计算结果表明所提出的自适应MBPE技术具有较高精度与可靠性。

带电高压线路对其他线路参数测定影响的探析

高压输电线路作为电网的重要组成部分,其参数测试的准确性会直接影响整个电力系统的可靠性与安全性,因此如何精确测量高压输电线路参数具有其重要的实际意义。对直流电阻、正序参数、零序参数、部分电容以及互感参数五个方面进行研究,基于传统测量方法进行改进,实现高压输电线路的带电测量,并通过理论修正,设立修正项或修正系数,使所测量的参数数据满足相应的工程需求,从而保证电网的正常运作,具有一定的经济与社会效益。

非全线并行架设的交、直流共用输电走廊线路间电磁耦合计算分析

为研究非全线并行架设、具有一定长度接近段的高压输电线路的电磁耦合变化规律,提出了适用于非全线并行架设的共用走廊高压输电线路电磁耦合的计算方法。通过算例,对影响共用走廊高压输电线路电磁耦合的主要因素进行了分析,结果表明：接近段长度及位置对非全线并行架设的共用走廊高压输电线路电磁耦合分量有较大影响。随着接近段长度的增加,静电感应电压、电磁感应电压和感应电流会逐渐增大。随着接近段首端与线路起点间距离的增加,线路首端、接近段两端的静电感应电压会逐渐减小,线路末端的静电感应电压则呈现先增大后减小的趋势;同时,线路首端的感应电流逐渐增大,而末端的感应电流逐渐减小,接近段两端的感应电流则先增大后减小。随着接近段与线路接地端间距的增加,电磁感应电压会逐渐减小。并计算了非全线并行架设输电走廊内直流线路接近段两端、线路两端电磁耦合分量及其沿线路的分布情况,进一步分析结果提出：对于非全线并行架设、具有一定长度接近段的交、直流输电线路,应根据线路间的电磁耦合分量水平合理选择接近段长度;接近段应选址靠近直流线路中部区域（即直流线路全长的20%～40%处）,并避免在直流线路两端有多条输电线路共用走廊的情况。