A transient current based double line transmission system protection using fuzzy-wavelet approach in the presence of UPFC

This paper presents a wavelet fuzzy based protection scheme for a double line transmission system with unified power flow controller. The protection scheme makes use of current signals at both the ends of transmission line which are synchronized with the help of global position system clock. A wavelet based multiresolution analysis is used to find the detailed coefficients of these signals which are utilized to calculate fault index. These fault indexes are compared with a threshold value to detect and classify faults on transmission system. The approximate decomposition of the current signals is utilized to locate the fault using Fuzzy logic from their respective terminals. The proposed algorithm has been tested successfully for various faults at different locations.     

Application of wavelet multiresolution analysis for identification and classification of faults on transmission lines

This paper presents a new method for identification and classification of faults based on wavelet multiresolution analysis (MRA). Daubechies eight (D-8) wavelet transforms of the three phase currents on a transmission line fed from both ends are used. The peak absolute value, the mean of the peak absolute values and summation of the 3rd level output of MRA detail signals of current in each phase extracted from the original signals are used as the criterion for the analysis. The effects of fault distance, fault inception angle and fault impedance are also examined. Extensive simulations are carried out to generate time domain input signal using EMTP (Microtran) on a 230 kV, 200 km long line fed from both ends and simulation results show that the proposed method is a simple, effective and robust method suitable for high impedance faults also.     

应用两端电流采样值二维空间映射分布特征的线路纵联保护

针对传统纵联保护在区外故障伴随电流互感器饱和时发生误动作的问题,提出一种基于线路两端电流采样值映射于二维空间分布特征差异的线路纵联保护新方案。该方案以线路两端电流采样点(母线指向线路为正方向)为坐标点映射于二维空间,在线路正常运行和外部故障工况下,映射点位于二维平面坐标系的第二、四象限;而内部故障工况下,映射点位于平面坐标系的第一、三象限。仿真和动模试验结果表明,所提方案能快速有效识别输电线路中出现的各类故障,对伴随电流互感器饱和及异常数据的故障也能正确识别。     

基于电压和电流突变量的高压直流输电线路保护原理

在对高压直流输电线路区内、外故障和雷击等暂态过程研究的基础上,提出了一种基于电压、电流突变量变化特征的高压直流输电线路主保护原理。该原理对两极线路同侧保护安装处测得的电压突变量幅值的比值设定阈值,选出故障极;利用故障线路两端电流突变量的极性在线路保护区内故障时相异、在区外故障时相同,区分线路上保护区内和区外故障。PSCAD/EMTDC软件对实际高压直流输电系统的仿真结果表明,该保护原理在双极两端中性点接地方式下能够快速判别故障极和区分线路上保护区内、外故障,可靠排除雷击干扰,在故障性雷击和高阻抗接地时准确动作,并适用于一极降压和一极全压运行、功率反送、一极停电检修及单极金属回线运行方式等。采样频率在10～100kHz范围内时可满足保护判据计算要求。     

A fast time–frequency transform based differential relaying scheme for UPFC based double-circuit transmission line

This paper presents a new differential relaying scheme for a mutually coupled, double circuit transmission line in presence of Unified Power Flow Controller (UPFC) in the line. The process starts at retrieving the three phase current signals at both ends of the transmission line synchronously and processing it though the time–frequency transform such as Fast Discrete S-Transform to derive the spectral energy content of the current signals. The differential spectral energy of current signals (difference between the spectral energy of the current signal at the sending and receiving ends, respectively) of the respective phases of transmission line is used to register the fault pattern. The proposed approach includes fault detection and classification along with identification of the fault section with respect to UPFC location in one of the double-circuit transmission line. The extensive test results indicate that the proposed differential relaying scheme is highly reliable in registering fault patterns in UPFC based transmission line including wide variations in operating parameters of the power network.     

基于单环定理的HVDC输电线路纵联保护方法

针对高压直流(high voltage direct current,HVDC)线路高阻接地故障时保护容易拒动的问题,提出一种基于单环定理的纵联保护方法。首先,将直流线路两侧电流突变量作为状态变量构造奇异值等价矩阵,根据单环定理进行谱分析从而实现区内外故障识别;然后,通过广义S变换提取两极电流突变量特定频段暂态能量和的比值特征进行故障选极;最后,给出了纵联保护方案。仿真验证表明,所提保护原理判据简单,易于整定,各种故障情况下均能实现快速、有选择性动作。所提方法对不良数据具有较强的免疫能力,即使在线路末端发生高阻接地等最不利于保护动作的故障情况下仍能可靠动作。     

Laboratory investigation of an amplitude comparator baseddirectional comparison digital protection scheme

A directional comparison digital protection scheme has been implemented with a 16-b single-board computer at each end of a physical model of a transmission line, with communication between the two ends. The protection algorithm makes use of the fundamental frequency components of the deviation signals of the voltage and phase-shifted current. Software routines have been developed for fault monitoring, directional determination, and the trip/block decision. Graphics features incorporated in the software are explained. Tests for various faults conducted on the physical model of a double-circuit transmission line show that the direction to a fault is determined in 3 to 7 ms. The blocking features of the relay are demonstrated     

智能电网继电保护研究的进展(一)——故障甄别新原理

利用故障暂态分量在区内故障时线路两侧功率方向相同、暂态能量大的特点,通过小波变换提取这些特征,实现超高压交流线路超高速保护、超高压母线超高速保护;利用直流输电线路端部的直流滤波器和平波电抗器对高频分量形成的阻抗边界,区内短路时高频分量远大于区外短路,使用高频能量在单端实现超高压直流线路全线超高速保护;利用中性点非直接接地系统单相接地时其暂态零序分量是工频分量几十倍并且不被补偿减小的特点,提取零序电流的高频分量,采用方向比较和幅值比较,实现了单相接地故障选线装置。给出了试验装置可以超高速(5ms内)判别故障性质的试验结果,展现了新的故障甄别原理可以满足智能电网中特高压系统对超高速切除故障的美好前景。     

基于暂态电压信号的输电线路保护算法研究

提出了一种基于双端电压暂态信号小波变换的高压输电线路快速保护算法。通过检测出的线路两端的电压信号小波变换模极大值点及其李氏指数的比较 ,区分出区内、区外故障或开关操作 ,保护动作可靠 ,能保护线路的全长 ,且对两端采样的同步要求不高。EMTP仿真对此算法进行了验证 ,对不同的故障位置和噪声情况进行了分析     

Novel transient-energy-based directionalpilot protection method for HVDC line

In long transmission lines, the charging current caused by the shunt capacitance decreases the accuracy in impedance based fault location. To improve the accuracy of fault location, this paper presents a novel scheme, where two Digital Fault Recorders (DFRs) are installed in a line. They can send the transient data of the faults to the both ends of a line. To estimate the distance of a fault, impedance based fault location methods are applied with transient fault data of both ends protection relays and both DFRs installed in a line. To evaluate the proposed scheme, a laboratory setup has been developed. In the lab, several faults have been simulated and associated voltages and currents are injected to a relay IED to compare experimental results.     

基于正序电流故障分量的输电线路故障检测

高压输电系统中传统后备保护定值整定困难,灵敏度易受到高阻接地、潮流转移等影响。文中提出了一种基于正序电流故障分量的输电线路故障检测算法。采用线路两端正序电流故障分量的矢量和幅值与矢量差幅值的比值作为线路的故障判断量,给出严格的公式推导,建立了故障检测的判据。理论分析了线路的故障判断量的分布特性,与本线路阻抗、两端背侧的系统等效阻抗、故障点位置的关系,证明了其与过渡电阻无关。在系统发生振荡时,将求解的故障定位值作为辅助判据。IEEE 39节点系统仿真实验表明,各类故障发生时所提算法均能够正确检测故障线路且不受故障位置、过渡电阻等影响,在非全相运行、负荷潮流转移时也能检测出故障线路,对两端数据的同步性要求不高。     

A new adaptive PMU based protection scheme fortransposed/untransposed parallel transmission lines

This paper proposes a brand-new adaptive phasor measurement unit (PMU) based protection scheme for both transposed and untransposed parallel transmission lines. The development of the scheme is based on the distributed line model and the synchronized phasor measurements at both ends of lines. By means of eigenvalue/eigenvector theory to decouple the mutual coupling effects between parallel lines, the fault detection and location indices are derived. The two proposed indices are used in coordination such that the internal and external fault events can be distinguished completely. By on-line estimation of the line parameters under the actual power system conditions, the proposed scheme will respond more accurately to power system faults. Extensive simulation results using EMTP have verified that the accuracy of the fault location achieved is up to 99.9%. The proposed protection system responds well and fast with regard to dependability and security. All the results show that the performance of the proposed detection/location indices is independent of fault types, locations, resistance, source impedance, fault inception angles, and load flows     

基于多小波包和人工神经网络的电力系统故障类型识别

采用PSCAD/EMTDC仿真500 kV高压输电线路不同工况下的故障.先对采集到的故障电流信号进行适当的多小波包分解,并计算各频带的能量,然后构造信号的多小波包特征向量,并以此向量作为训练样本对BP神经网络进行训练,当输电线路发生故障时,将提取的故障电流信号的多小波包能量特征向量输入训练好的BP神经网络,即可实现故障类型的识别.仿真结果表明采用多小波包提取的故障电流特征量比采用传统小渡包提取的特征量信息更丰富,对人工神经网络的训练效果更好,网络识别精度具有明显优势.     

A useful methodology for analyzing distance relays performanceduring simple and inter-circuit faults in multi-circuit lines

A methodology for evaluating and visualising the response of power system distance protection units most commonly used is presented. A general case, with different topologies, of a double-circuit transmission line is considered and different types of inter-circuit faults are treated. Single line and simple faults are simplified cases of the general one. Faults are treated by means of the adequate connection between the sequence networks, where different types of faults are represented by a resistance star associated to both lines and ground. Different combinations of these resistances result in different types of faults. Fault conditions are introduced to sequence networks of the rest of the system through phase current controlled current sources, and the resulting sequence voltages at the fault point are applied to fault resistances through sequence voltage controlled voltage sources. To calculate faults the mesh analysis method has been modified to take into account the dependencies fixed by the controlled sources. Real previous state of the power system (load flow, sequence source impedances at both ends and sequence impedance between ends) is taken into account. A useful and reliable way of representation is presented to obtain the expected response of different types of distance units in multi-circuit lines in presence of inter-circuit simultaneous faults     

Transmission lines differential protection based on the energy conservation law

This paper proposes a differential protection scheme for transmission lines using the energy conservation law. The real power signals at both ends (sending and receiving) of the line are compared with a pre-specified value, if the resultant is more than this value, an internal fault is indicated in the transmission line zone.The proposed technique is evaluated using PSCAD/EMTDC program configurated to model the effect of faults on typical 500 kV transmission line. Extensive simulation studies show that this protection scheme has the ability to discriminate internal faults fast and accurately, and is more reliable than conventional biased differential protection scheme, and suitable for all types of lines. Details of the proposed relay design are given in the paper; also results of some performance studies are given.     

A novel adaptive PMU-based transmission-line relay-design and EMTP simulation results

This paper proposes a novel adaptive relaying scheme based on phasor-measurement units (PMUs) for transmission lines. The proposed adaptive relaying scheme can provide an extremely accurate discrimination between in-zone and out-of-zone faults. Two novel and composite fault discrimination indices in terms of Clarke components of synchronized voltage and current phasors at two ends of a line are derived. A line parameter estimation algorithm is developed and built in the newly designed relay to solve the uncertainty problem of line parameters. The proposed relaying scheme is independent of fault types, fault locations, fault path resistance, fault inception angles, and the variations of source impedance. The tripping decision time of the designed relay is very fast and almost held well within 6 ms for most fault events. All of the EMTP simulation results show that the proposed adaptive relaying scheme provides a high level of dependability and security.     

一种新的电力线路短路故障测距算法的研究

本文提出了一种瓣的电力线路故障精确测距算法。该算法仅利用线路两端的故障后电压、电流向量测量值。     

广域保护中基于能量守恒原理的母线及输电线差动保护

提出一种基于能量守恒原理的纵联差动保护,对线路两端或母线各端的有功功率进行比较,若各端功率的和超出整定值,则判定为区内故障。在典型400 kV输电系统模型上,运用MATLAB仿真软件对所提出的原理进行了仿真验证。仿真结果表明,该方法比传统电流比率差动保护更加可靠且计算量小,因而可缩短动作时间。该方法能检测所有故障类型,适应于超高压远距离输电线路。     

基于斯皮尔曼等级相关系数的新能源送出线路纵联保护

新能源电源均直接或间接通过电力电子装置并网,其故障电流幅值受限、相角受控、谐波含量高、波形非线性度强,与传统同步电源有着明显区别。传统比率制动式差动保护的动作性能面临挑战。为解决该问题,文中提出了基于斯皮尔曼等级相关系数的送出线路纵联保护方法。当正常运行或者区外故障时,流过送出线路的是穿越性电流,因此两侧电流波形完全相反。当发生区内故障时,两侧暂态电流波形存在巨大差异,因此可以利用斯皮尔曼等级相关系数量度两侧电流波形的相关程度,从而区分区内、区外故障。该方法适用于各类新能源场站,且具备较好的抗过渡电阻和抗噪声能力。同时,与现有基于新能源故障特征的保护相比,该方法在新能源弱出力以及重合于永久性故障时也表现出了较好的动作性能。仿真结果和现场录波数据均证实了该方法的有效性。     

海上风电柔性直流送出线路的纵联保护方法

海上风电柔性直流送出系统常采用伪双极接线.当发生单极接地故障时,电流纵联保护不能可靠地区分区内、外故障.针对该问题,提出了一种适用于海上风电柔性直流送出线路的行波方向纵联保护方案.分析了伪双极直流系统的单极接地故障特征,提出了电流纵联保护在海上风电柔直送出线路的问题.基于行波原理,提出了不受暂态分布电容电流影响的保护方...