Fault location of two-parallel transmission line for double phase-to-earth fa ult using one-terminal data

INTRODUCTIONTransmissionlinesofapowersystemaresubjecttomanykindsoffaults.Theprincipaltypesare :phase to earth ;doublephase to earth(phase phase earth) ;phase to phase ;three phase.Followingtheoccurrenceofatransmis sionlinefault,themaintenancecrewmustfinda…     

Single phase-to-ground fault line identification and section location method for non-effectively grounded distribution systems based on signal injection

A diagnostic signal current trace detecting based single phase-to-ground fault line identifica- tion and section location method for non-effectively grounded distribution systems is presented in thisi oaper. A special diagnostic signal current is injected into the fault distribution system, and then it is de- tected at the outlet terminals to identify the fault line and at the sectionalizing or branching point along the fault line to locate the fault section. The method has been put into application in actual distribution network and field experience shows that it can identify the fault line and locate the fault section correctly and effectively.     

Modern travelling wave based fault location techniques for HVDC transmission lines

The modern travelling wave based fault location principles for transmission lines are ana-lyzed. In order to apply the travelling wave principles to HVDC transmission lines, the special tech-nical problems are studied. Based on this, a fault locating system for HVDC transmission lines is developed. The system can support modern double ended and single ended travelling wave princi-ples simultaneously, and it is composed of three different parts: travelling wave data acquisition and processing system, communication network and PC based master station. In the system, the fault generated transients are induced from the ground leads of the over-voltage suppression ca-pacitors of an HVDC line through specially developed travelling wave couplers.The system was applied to 500 Kv Gezhouba-Nanqiao(Shanghai)HVDC transmission line in China. Some field op- eration experiences are summarized, showing that the system has very high reliability and accu- racy,and the maximum location error is about 3 km(not more than 0.3% of the total line length). Obviously, the application of the system is successful, and the fault location problem has finally been solved completely since the line operation.     

一种T型输电线路行波故障测距方法

为进一步提高T型输电线路故障测距的准确性,提出了一种基于小波变换的T型输电线路行波故障测距方法。首先将在各测量点采集到的行波信号进行相模变换;其次将得到的α模分量进行小波变换,得到行波波头首次到达各测量点的时刻;最后判别出故障支路,并计算出故障距离。大量的MATLAB仿真实验结果表明,所提方法不受过渡电阻、故障类型、行波波速等因素的影响,测距误差较小,具有较高的精确性和适用性。     

Effects of un-transposed UHV transmission line on fault analysis of power systems

The conventional fault analysis method based on symmetrical components supposes that the three-phase parameters of un-transposed transmission line are symmetrical in case of fault. The errors caused by the method with the symmetrical distributed parameter circuit model as the equivalent circuit of the un-transposed ultra high voltage (UHV) transmission line were studied under both normal operation and fault, and the corresponding problems arising were pointed out. By contrast with electromagnetic transient and power electronics (EMTPE) simulation results with the asymmetrical distributed parameter circuit model of un-transposed line, it is shown that the conventional method cannot show the existence of negative and zero sequences before fault happening and there are many errors on voltage and current after fault happening which are different with fault types. The error ranges of voltage and current are 2.13%-81.13% and -7.82%-86.15%, respectively.     

Inter-Circuit Fault Location Algorithm for Two-Parallel Transmission Line

Transmissionlinesformthebackboneofpowerutilityoperationsandachievethecontinuityofservicefromgenerat ingplantstotheusers.Linesaresubjecttomultifariouskindsoffaultsbecausetheyareexposedtotheelements .Thecausesoffaultaremultifarious .Linefaultmaybetriggeredbylight ningstrokes.Treesmayfallacrosslines .Fogandsaltsprayondirtyinsulatorsmaycausetheinsulatorstringstoflashover.Iceandsnowloadingmaycauseinsulatorstringstofailmechanically .Followingtheoccurrenceofalinefault,itisnecessaryforthemaintenance…     

基于USB-4220数据采集卡的小电流接地系统故障选线实验平台设计

小电流接地系统故障选线是电力系统继电保护课程教学中的难点,为了更好地使学生掌握这一内容,设计了一种基于USB-4220数据采集卡结合上位机控制的故障选线实验平台.硬件装置中采用了具有多通道同步采集功能的数据采集卡,并设计了不同类型的可调整滤波电路.采集并记录实验数据及波形,对不同继保算法进行横向比较,完成判据指标分析,...     

A new class of negative refractive index transmission line

We propose a new class of negative refractive index transmission line in which ideal operational amplifiers are applied to form the periodically loaded negative-impedance-converted inductors and capacitors. The phase response of the new trans-mission line is opposite to that of a positive refractive index conventional transmission line. Unlike the existing negative refractive index transmission line,the new negative refractive index transmission line is non-dispersive and thus can lead to many novel applications such as designing new broadband devices.     

高压架空输电线故障测距及实现方案

根据各测距算法采用的原理不同,将现有的各种测距算法分为行波测距、单端测距和双端测距三类。然后逐类对各种算法的理论基础和应用条件进行了分析、对比和讨论,并在此基础上总结出了各测距算法的优点及存在的问题,指出了每种测距算法的适用范围和应用局限性。最后,对高压架空输电线路故障测距进行现场实验及研究,并对其应用前景进行了展望。     

基于EMD的消弧线圈接地系统故障选线

提出基于EMD和相对能量法相结合的消弧线圈接地系统故障选线方法．通过EMD时空滤波,在故障线路零序电流中提取暂态分量作为特征量,再求得各线路的相对能量,以能量为故障判据,从而检测出故障线路,经Matlab／simdlink仿真验证,结果表明该方法有效,且算法简便．     

Science Letters: Lattice type transmission line of negative refractive index

In this letter, we introduce a novel passive transmission line of negative refractive index （i.e., left-handedness） based on identical symmetrical lattice type structures [thus called ＂lattice type transmission line＂ （LT-TL）]. The dispersion characteristic and the transmission response of the proposed LT-TL are analyzed. While all the other left-handed passive transmission lines are of high pass, the present passive left-handed transmission line is of low pass. Compared with a conventional transmission line, the LT-TL has a phase shift of 180° in the entire wide pass-band.     

Science Letters: Lattice type transmission line of negative refractive index

In this letter, we introduce a novel passive transmission line of negative refractive index (i.e., left-handedness) based on identical symmetrical lattice type structures [thus called "lattice type transmission line" (LT-TL)]. The dispersion characteristic and the transmission response of the proposed LT-TL are analyzed. While all the other left-handed passive transmission lines are of high pass, the present passive left-handed transmission line is of low pass. Compared with a conventional transmission line, the LT-TL has a phase shift of 180° in the entire wide pass-band.     

Wind turbine fault detection based on SCADA data analysis using ANN

Wind energy is one of the fast growing sources of power production currently, and there is a great demand to reduce the cost of operation and maintenance. Most wind farms have installed supervisory control and data acquisition （SCADA） systems for system control and logging data. However, the collected data are not used effectively. This paper proposes a fault detection method for main bearing wind turbine based on existing SCADA data using an artificial neural network （ANN）. The ANN model for the normal behavior is established, and the difference between theoretical and actual values of the parameters is then calculated. Thus the early stage of main bearing fault can be identified to let the operator have sufficient time to make more informed decisions for maintenance.     

Science Letters:A power divider based on a new kind of composite right/left-handed transmission line (CRLH TL) unit

INTRODUCTION Wave propagation in a material with negative magnetic permeability and negative electric permit- tivity was first theoretically analyzed by Veselago (1968). In such a left-handed material (LHM), the electric field E, the magnetic field H and the wave vector k of electromagnetic wave propagation obey the left-hand rule (instead of the right-hand rule for usual materials). After Smith et al.(2000) demon- strated simultaneously negative permeability and permittivity, using cop…     

电磁场传输线理论仿真实验的设计与实现

通过对传输线理论教学内容及教学中存在问题的分析,针对传输线3种工作状态、行驻波瞬态分布以及基于Smith圆图的阻抗匹配等教学内容,设计并实现了传输线理论仿真实验。该实验内容突出知识的综合性与应用性,以达到良好的教学效果。     

《直线和线段》导课设计种种

直线和线段是几何初步知识中的起始概念 ,也是进一步学习平面图形的基础 ,这两种线有别于学生在生活中见到的各种实物“线”。为使抽象的概念得到生动的掌握 ,笔者根据直线和线段的共性和个性 ,结合教学的重点难点 ,设计了几种既形象又有趣的导课方法 ,均收到了较好的效果     

非视距环境下基于散射体信息的被动定位(英文)

为了提高传统的TOA/AOA定位技术在非视距环境下的定位精度,提出了一种基于散射体信息的混合定位方法.首先,利用基站坐标信息和TOA测量值确定线性化的可行区域,产生移动台的候选位置点.对每一个移动台候选点,结合TOA和AOA测量值,计算各自散射体半径,通过与先验的散射体信息的比较,筛选候选移动台位置点.然后,运用自适应模糊聚类算法估计移动台位置,完成定位.最后,对所提出的定位算法进行了仿真验证.仿真结果表明:所提出的基于散射体信息的混合TOA/AOA定位算法能够减轻非视距效应,有效估计移动台位置.     

Rotor broken bar fault diagnosis for induction motors based on double PQ transformation

A new rotor broken bar fault diagnosis method for induction motors based on the double PQ transformation is pre-sented. By distinguishing the different patterns of the PQ components in the PQ plane,the rotor broken bar fault can be detected. The magnitude of power component directly resulted from rotor fault is used as the fault indicator and the distance between the point of no-load condition and the center of the ellipse as its normalization value. Based on these,the fault severity factor which is completely independent of the inertia and load level is defined. Moreover,a method to reliably discriminate between rotor faults and periodic load fluctuation is presented. Experimental results from a 4 kW induction motor demonstrated the validity of the proposed method.     

双线螺纹的车削方法

螺纹的车削是车工生产习中较为重要的课题，相对他课题来说是比较难的课题，对于一般的单线螺纹学生尚能掌握，而多线螺纹车削步骤较为复杂，操作者应据具体的螺纹，认清步骤，掌握方法，才能保证其车削精度和其他加工质量。     

对零序有功功率选线方法的探讨

对自动跟踪消弧线圈接地系统进行了仿真研究.结果表明:零序功率震荡和采样误差是造成零序有功功率选线方法不准的两个主要因素.为了减小这两个因素的影响,对零序有功功率选线方法的模型进行了改进,并利用MATLAB软件对改进模型进行了验证.