同塔四回输电线路故障选线新方案

从参数不对称同塔四回输电线路入手,结合四回线内部存在的线间及相间电磁耦合的特点,分析推导出适合的相模变换矩阵对各回线阻抗进行解耦处理,并且通过仿真对比的方式论证了解耦方法的正确性。基于解耦出的独立模量间的关系,定义4个参数K_1—K_4,根据这4个参数在不同回路故障时的取值不同,构造新的故障选线判据。大量的PSCAD/EMTDC仿真数据表明,所提出的故障选线方案速度快、简单、可靠,且不受故障距离、过渡电阻以及负荷电流和系统运行方式的影响。     

One-end fault location method for untransposed four-circuit transmission lines

This paper presents a fault location method suitable for untransposed four-circuit parallel transmission lines using the data available at one end of the line. The proposed method employs an accurate distributed parameter line model that fully accounts for mutual coupling between all the lines and shunt capacitance effects. The fault location algorithms are developed in phase-components, one for the case where the fault is in any one of the circuits, the second for the case where the fault involves any two circuits and the third for the case where the fault involves more than two circuits. The proposed method is tested using the transient data obtained by simulating a 500-kV four-circuit overhead transmission line under different fault conditions. The simulations are done using the software “DIgSILENT PoweFactory”. Results obtained indicate that the method is capable of estimating the fault distance with high accuracy for various fault conditions. Also the robustness of the fault location method is investigated.     

一种同杆并架双回线接地距离保护方案

距离保护应用于同杆并架双回线时其动作性能受零序互感的影响.通过对同杆并架双回线接地故障时零序电流特点以及零序互感对接地距离保护影响的分析,指出两回线零序电流反向是同杆并架双回线接地距离保护误动的主要原因,根据两回线零序电流反向时,故障线路的零序电流大于非故障线路,提出了一种逻辑判断的零序电流补偿方法.数字仿真的结果表明,该方法提高了同杆并架双回线距离保护的性能.     

同塔混压四回线下的单回线故障零序方向元件动作特性分析

同塔混压四回线发生故障时,由于近距离物理条件,不仅要考虑相间互感,也要考虑不同电压等级系统之间的互感对故障分析及保护产生的较大影响。针对弱电强磁与强电联系两种场景下同塔混压四回线中单回线发生接地故障的情况,首先阐述零序去耦等值电路的建立依据,然后对零序方向元件的动作特性及主要影响因素进行理论分析。结果表明对于弱电强磁场景,不同电压等级之间的零序互感对零序方向元件动作行为的影响可以忽略不计。对于强电联系场景,零序互感、电气强度及故障位置综合影响零序方向元件的动作行为。基于ATP-EMTP建立1 000 kV/500 kV同塔混压四回线模型,对单回线故障条件下的零序方向元件动作行为进行了建模仿真,验证了理论分析的正确性。     

First-zone distance relaying algorithm of parallel transmission lines for single-phase to ground faults

A novel zone-one distance relaying algorithm for single phase to ground faults on parallel lines is proposed. The proposed algorithm only requires sampled current and voltage values at one end of the protected line to calculate the fault impedance. The adjacent circuit zero-sequence current can be calculated from the protected circuit zero-sequence current and without cross-connection. The algorithm can overcome the issues of overreach and under-reach. The study in this paper shows that the new algorithm has higher reliability than that of conventional distance relays with and without cross-connected zero-sequence current compensation. Therefore, the algorithm optimizes the performance of zone-one distance relaying for parallel transmission lines. The results are verified by the simulations using PSCAD software.     

A novel fast distance relay for long transmission lines

The measuring accuracy and the measurement stability of conventional distance relay will be influenced by complex and remarkable harmonic components due to the large capacitance of the line when it is used for a long line. Correspondingly, the tripping speed will be delayed to some extent. To solve this problem, a fast distance relay for long transmission lines is presented, which is on the basis of the differential equation algorithm using π transmission line model and the theory of Equal Transfer Process of Transmission Lines (ETPTL). The shortcomings of π model differential equation algorithm due to the impact of high frequency components can be overcome by using a low-pass filter. The problem resulting from the difference between the transfer feature of the voltages used by the distance protection and that of the currents due to the transient characteristic of coupling capacitor voltage transformers (CCVT) can be solved by using virtual digital CCVT. Then, the new distance relay can trip quickly by re-structuring the voltage at the fault point and iterative calculations. A variety of ATP simulation tests show that the new relay has fast tripping speed and high reliability when applied to the long transmission lines.     

同塔四回线参数解耦及故障分析方法

同塔四回输电线路参数复杂,难以进行故障分析.针对实际同塔四回线路杆塔结构和线路排布特点,采用矩阵变换理论,提出了同塔四回线参数解耦算法,将四回线线路参数矩阵解耦为四回线相关联的一组双回同向序量和三组双回反向序量.该算法计算简单,物理意义明确.以上述解耦算法为前提,提出了同塔四回输电线路复合序网故障分析方法,并给出了一回线内故障的复合序网图.本方法考虑了同塔四回线的序量特点,为其新型保护原理开发和整定计算奠定了理论基础.EMTDC仿真验证了上述算法的正确性.     

A novel fast distance relay for series compensated transmission lines

This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines.     

一种适用于MMC-HVDC直流输电线路的保护新原理

模块化多电平换流器(Modular Multilevel Converter,MMC)作为一种新型多电平拓扑结构的电压源换流器,具有扩展性强、输出电压质量高、谐波含量少等优点,已经展现出极其重要的工程应用前景。首先介绍了模块化多电平高压直流输电(Modular Multilevel Converter based High Voltage Direct Current,MMC-HVDC)的拓扑结构及运行原理,然后通过故障附加状态网络分别对区内和区外故障进行了分析,并利用二阶微分法提取了故障时电压、电流的故障分量,得出了保护策略。根据故障网络分析可知,当直流线路发生区内故障时,电流故障分量极性相同;当直流线路发生区外故障时,电流故障分量极性相反。因此,可以根据电流故障分量的极性是否相同来识别区内、外故障,利用二阶微分法来提取故障时电流的故障分量,用以识别区内、外故障。另外,根据故障网络分析还发现,当直流线路发生区内故障时,单极故障时电压故障分量极性相同,双极故障时电压故障分量极性相反。因此,可以根据电压故障分量的极性是否相同来识别故障极。利用二阶微分法来提取故障时电压的故障分量,根据电压故障分量的极性,识别故障所在的极。最后利用PSCAD电磁暂态仿真软件建立了MMC-HVDC的仿真模型。仿真结果验证了故障分析以及保护方法的正确性。     

Adaptive distance relay setting for parallel transmission network connecting wind farms and UPFC

The paper presents an adaptive distance relay setting for parallel transmission network connecting wind farms. The ideal trip characteristics of distance relay is greatly affected in presence of mutual coupling of parallel transmission lines as the apparent impedance is significantly affected. Similarly, the reach setting of the relay for the lines connecting wind farms is significantly affected as the relay end voltage fluctuates continuously. Thus, the proposed study focuses on developing adaptive relay setting for parallel transmission network including wide variations in operating conditions of wind farms and effect of mutual coupling, together. Further, the performance of the proposed adaptive relay setting for parallel lines including Unified Power Flow Controller (UPFC) indicates the potential ability of the proposed analytical approach in handling distance relaying in transmission system.     

Protection of parallel transmission lines using wavelet transform

A new scheme to enhance the solution of the problems associated with parallel transmission line protection is presented in this paper. The scheme depends on the three line voltages and the six line currents of the two parallel lines at each end. Fault detection, fault discrimination, and calculation of the phasors of the measured signals are done by using wavelet transform (WT). By comparing the magnitudes of the estimated current phasors of the corresponding phases on both lines, internal faults on the parallel lines can be identified. Also, by calculating the distance element of the phases on which a disturbance is detected and having a very small current difference magnitude can enhance and strengthen the scheme. Studies show that all types of faults at different loading conditions can be correctly identified in less than one cycle of the fundamental frequency.     

Performance of distance relay mho elements on MOV-protectedseries-compensated transmission lines

It is shown that the applicability of memory-polarized distance relay mho elements to the protection of MOV (metal oxide varistor) protected series-compensated lines is dependent on the system configuration, line loading, the location of the potential source, and the magnitude of memory polarization. For a configuration with compensation at one end of a line, the results indicate certain advantages in using the potential from the line side of the capacitor, and the use of a relatively large magnitude of memory polarization. The presence of a conducting MOV enhances the performance of the mho element both in terms of security on reverse faults and dependability on forward faults. The results obtained pertain to the proposed application in the Ontario Hydro system of a relatively large amount of compensation at one terminal in each circuit of a double-circuit line     

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     

混压同塔四回线路跨电压故障选相元件动作分析与对策研究

混压同塔四回线发生跨电压故障时,零序互感的存在会对各相故障电流产生较大的影响。针对混压同塔四回线路中发生跨电压不接地故障的情况,主要分析了故障相电流的特征及电流选相元件的动作情况,采用改进复合序网的方法求解故障电流。利用相量图详细讨论了跨电压故障的电流特征及其对相电流差突变量选相元件的影响。针对混压同塔线路跨电压故障可能存在的误选相问题,提出一种基于相电流差突变量与相电流突变量相结合的综合选相方案,以实现正确选相。基于PSCAD/EMTDC对混压同塔四回线的各类跨电压故障进行大量仿真实验,验证了理论分析的准确性。     

500kV同塔4回线路真型塔冲击电压的试验研究

江苏利港电厂泰北变电站到梅里的500 kV是国际上第一条同塔4回线输电线,介绍了该同塔4回线路真型塔的雷电冲击和操作冲击电压的试验过程,重点论述了用两台冲击电压发生器进行的试验方法、试验项目、试验结果,最后给出了真型塔各回路(对地、相间)雷电和操作波电压下的50%放电电压短尾波雷电等试验结论.关键词:500 kV;同塔4回;输电线路;真型塔作者简介:潘震东(1957-),男,华东电网有限公司副总经理,高级工程师,主要从事电网建设、研究与管理工作.     

基于故障录波信息的输电线路继电保护内部故障在线检测方法

提出一种基于故障录波信息的输电线路继电保护内部故障在线检测方法,通过对故障录波装置现有启动方式进行必要的扩展,利用故障录波装置记录的动态信息为依据,从而实现对输电线路中保护装置内部故障进行在线检测.应用此方法,能够对正确揭示和描述电力系统隐藏故障提供一条有效途径.通过原理分析及举例说明,验证了此方法的合理性.     

基于故障录波信息的输电线路继电保护内部故障在线检测方法

提出一种基于故障录波信息的输电线路继电保护内部故障在线检测方法,通过对故障录波装置现有启动方式进行必要的扩展,利用故障录波装置记录的动态信息为依据,从而实现对输电线路中保护装置内部故障进行在线检测。应用此方法,能够对正确揭示和描述电力系统隐藏故障提供一条有效途径。通过原理分析及举例说明,验证了此方法的合理性。     

基于分离模型的双回平行输电线路可靠性评估

提出了基于分离模型的考虑独立停运、共因停运和相关停运的双回平行输电线路可靠性评估模型,解决了传统的评估模型计算量大等缺点,在电力系统中双回路使用越来越多的情况下,使可靠性评估计及其他停运模型的影响成为可能。该模型可以很容易地计及不同的停运模型,采用交集的概念计算系统的失效概率和等效故障率,并分析不同停运模型对系统故障率的影响,算例分析验证了分离模型的有效性。     

A digital protection technique for parallel transmission linesusing a single relay at each end

A novel digital relaying technique for parallel transmission lines is presented. Only one relay at each end of the two lines is used. The idea of the protection algorithm is based on the comparison of the average current of corresponding phases. The technique is simple and avoids many problems of parallel lines. Simulation studies show that the trip signal is generated about 5 ms after the inception of the fault. The stability of the relay under different operating conditions is also examined     

基于电流双反相量的同杆四回线故障选相方法

为了解决同杆四回线故障情况复杂,跨线故障时无法应用单回线故障选相方法的难题,提出了一种基于故障电流双反相量的同杆四回线故障选相方法。同杆四回线发生一回线内或两回线间跨线故障时,对四回线各相电流进行变换,可得故障相电流的双同及双反相量。通过对故障电流边界条件的分析可知,不同类型故障时故障电流的3个双反相量分别具有不同的幅值和相位特点。以此为基础,提出了在一回线内故障和两回线间跨线故障时能够准确识别故障回线和故障相的同杆四回线故障选相方法。仿真表明本方法在不同的负载电流、过渡电阻、故障位置及故障类型下均能进行有效的故障选相。