用于特高压输电线保护的能量方向元件

传统能量方向元件在特高压线路中不能正确判别故障方向,同时当线路出口发生故障时由于系统内阻很小而导致有功能量方向元件也不能做出正确的判断。提出了一种应用于特高压长距离输电线路的故障分量式能量方向元件,并且提出了相应的方向纵联保护原理,用贝瑞隆算法加以实现;从而使保护的可靠性大大提高;分析了保护判据及其动作特性。通过数字仿真证明了所提方向元件原理和保护判据的正确性和可靠性,该元件具有不受系统暂态过程、过渡电阻、串补电容等因素影响的特性,而且其灵敏度不受故障类型及故障位置等因素的影响,同时动作速度也较快,不大于20ms。     

Fast and accurate parameter estimation algorithm for digital distance relaying

Response of digital distance relaying depends on the fast and accurate calculation of parameters such as voltage and current phasors and fault impedance. This paper describes a new apparent impedance estimation algorithm that is based on modal components theory. It is shown in the paper that the proposed algorithm has several advantageous features in terms of speed and accuracy over previously suggested symmetrical and modal components based algorithms. The paper discusses a procedure for deriving a fault impedance estimation algorithm that can be used for protecting power transmission lines. The proposed algorithm was evaluated using an alternative transient program (ATP). The program models a power system, simulates many fault conditions on a selected transmission line and generates fault data. The relay software then obtains filtered, scaled and sampled data and calculates fault impedance using the proposed algorithm. The relay characteristic makes trip decisions based on the fault impedance estimates. The paper shows the feasibility of the proposed algorithm for first zone distance protection. Some results of these studies are presented and discussed in the paper.     

基于故障分量的配电网单端量测距方法

为了消除负荷电流对配电网单相接地故障测距精度的影响,提出了基于故障分量的单端量测距方法。该方法根据横向故障电流的特征构造了测距函数,利用线路单端电压、电流的故障分量来计算故障距离。大量的ATP-EMTP仿真结果表明该方法不受负荷电流的影响,可以有效地搜索到配电网多分支线路的故障点或故障范围。     

基于相间故障弧光电压特征的高压线路选相元件

提出了一种基于相间故障弧光电压特征的高压线路选相新原理,应用于振荡闭锁期间的选相元件.对接地故障,利用零、负序电流相位差进行分区,每个分区包括某相单相接地和另外两相短路接地两种故障.然后根据相间故障弧光电压Ucosψ小于某一定值,而健全相相间电压的余弦值Ucosψ一般比较大的特征,来得到选相结果,解决了目前选相元件在电力系统振荡时可能发生的误选相问题.通过对不对称故障开放条件的改进,大大提高了单相接地故障的选相速度.该选相元件具有很强的耐过渡电阻能力,并且完全不受分支系数和系统运行方式的影响.RTDS试验验证了新选相元件的准确性和有效性.     

A FAULT LOCATION ALGORITHM FOR TRANSMISSION LINES

ABSTRACT

This paper presents an algorithm for the computation of fault location for a transmission line by means of the voltage and current signals, acquired by the digital distance relays at both the terminals of the line. Based on the proposed algorithm, the fault distance can be calculated accurately and quickly, even though the two digital distance relays are of different types with different sampling frequencies. This proposed fault location method is suitable for the condition that there are communication links between a power grid dispatch centre and the digital distance relays.     

A new distance relaying algorithm based on complex differential equation for symmetrical components

This paper presents a new digital impedance measuring technique for transmission lines that combines symmetrical components and the complex differential equation of an equivalent fault loop circuit. The phase voltages and currents at the relaying point are transformed into symmetrical components using Fourier filters of short window length. Depending on fault type, an appropriate fault loop circuit is formed, signals of which are the appropriate symmetrical components, while a parameter of which is the positive sequence impedance being a geometrical measure of the distance from the relaying point to a fault. The impedance, however, is measured very fast by on-line solving the complex differential equation originated for this fault loop circuit. Consequently, this approach combines frequency domain estimation of symmetrical components (accurate filtration) and time domain measurement of positive sequence impedance (high speed response).

The presented method suits well the protection of parallel lines against high-resistance faults occurring very close to the far end of a line. A new method is proposed for detecting high-resistance faults and deciding which line out of two parallel lines actually suffers a fault.

The included EMTP test results demonstrate the efficiency of the proposed relaying algorithm.     

基于故障电流分布因子的单端故障定位方法

为了实现电力电缆的精确定位,提出了一种基于故障电流分布因子的单端故障定位方法。该方法首先根据Kirchhoff电压定理对电力系统等效模型建立表达式,然后检测线路单端三相电压、电流的正序、负序以及零序分量,接着引入故障电流分布因子,用故障类型的加权系数以及故障电流增量值替代故障电流,建立故障定位函数,最后检测出故障距离。仿真实验表明该方法鲁棒性强且具有较高的精确性。     

基于故障信息的高阻接地故障辨识与定位方法

高压输电线路发生高阻接地故障时,由于受过渡电阻的影响,线路保护动作行为较为复杂,故障测距结果往往误差过大。针对以上问题,提出了一种高阻接地故障辨识和故障定位的方法。该方法的核心思想是基于故障录波数据,计算故障区域各条线路两侧电流矢量和及跳闸线路两侧零序电流比值,然后根据序网络故障分析和差动保护原理,利用电网分布式继电保护计算系统进行故障辨识和定位。计算和现场巡线结果表明该方法受过渡电阻和负荷电流的影响很小,故障定位精度较高,可满足现场的应用要求。     

Adaptive algorithm for transmission line protection in the presence of UPFC

The presence of flexible ac transmission system (FACTS) controllers in transmission lines causes mal-operation of distance relays. The series-shunt FACTS devices have larger influence on the performance of the relays compare to the other FACTS controllers. Furthermore, high-resistance fault is another factor that relay become under-reach and cannot correctly identify the fault. In this paper, a method is provided based on synchrophasors to eliminate the effects of unified power-flow controller (UPFC) and fault resistance on the distance relay. In the presented method, the data of voltage and current signals of buses will be sent to system protection center (SPC). In SPC, an algorithm is provided based on active power calculation in buses which is able to eliminate the effects of both mentioned factors. The main advantage of the proposed method, in addition to the simplicity of the algorithm, is the ability to operate in all types of faults and in high-resistance faults. Furthermore, a technique is presented in this paper to calculate UPFC data. A comparison has been performed between this technique and another method where UPFC data is directly transmitted to SPC by communication channel. In modeling of UPFC, detail model is used based on 48-pulses voltage source converters.     

Fault impedance estimation algorithm for digital distance relaying

Fault impedance is one of the major parameters that must be estimated accurately in digital distance relaying application. In this paper, a new algorithm is proposed based on symmetrical components theory. The proposed algorithm has computational advantage over previously suggested symmetrical components based algorithms. A procedure for applying shunt fault conditions to the sequence equations to estimate fault impedance of the protected transmission line is discussed. The Alternative Transient Program (ATP) that is available on personal computers was used in evaluating the proposed algorithm. ATP models a power system and simulates many fault conditions on a selected transmission line. Fault data obtained were used in calculating fault impedance using the proposed algorithm. Fault impedance estimates were inserted in relay characteristics to determine suitability of the proposed algorithm for first zone distance protection. Sample results of these studies which show stable fault distance estimates are presented and discussed in the paper     

高压输电线路距离保护克服过渡电阻能力研究

高压输电线路中存在较大的过渡电阻,很容易引起距离保护拒动或误动.分析特高压单侧电源经长线路出口故障和双侧电源长线路出口故障时过渡电阻对距离保护工作的影响,探讨单侧电源助增电流网络、外汲电流网络中过渡电阻对测量阻抗的影响,并给出2种网络结构在不同地点处保护测量阻抗的计算公式.研究能较好躲过渡电阻特性的零序电抗继电器、自适应接地距离继电器、神经网络距离继电器,分析比较不同方法的优缺点及适用场合.     

Real-time assessment of a symmetrical component and microcontroller based distance relay

This paper presents the design, implementation and real-time assessment of a microcontroller based digital distance relay that can be used for the protection of power transmission lines. The proposed design is implemented using a general-purpose Intel 8097 microcontroller and custom-made filters, operational amplifiers, sample-and-hold amplifiers, multiplexers, and analog-to-digital converters. The relay software is based on a computationally efficient symmetrical component based fault distance estimation algorithm. Results of the performance assessment studies on this algorithm have shown promising fault distance estimates for first-zone faults on the protected transmission line. Real-time implementation of the symmetrical component based fault distance estimation algorithm is presented and discussed in this paper. Hardware and software tools were used to design and fabricate a microcontroller based distance relay using the above-mentioned algorithm. This paper describes details of the design of the distance relay. A test setup in the laboratory using a transmission line model was used to generate data to assess the real-time response of the designed relay. High-speed relay operation of the order of one cycle is demonstrated in the test results.     

基于电流信号包络线故障熵的超高压输电系统振荡中再故障识别算法

针对超高压输电系统振荡对距离保护的影响,提出一种用互差2p/3电角度的三点电流瞬时值提取三相电流包络线的近似算法,在此基础上利用各相电流包络线故障熵的差值变化特征来识别输电系统振荡中的再故障情况,使得距离保护的振荡闭锁装置能够在系统故障时及时开放保护。仿真实验表明该算法在纯振荡情况下可靠不误动,并且可以快速有效地识别系统振荡中发生的各种故障。该算法实现方便,计算量小,具有工程实用价值。     

Digital protection of transmission lines using block pulse functions

An application of block pulse functions for digital protection of transmission lines is presented. A digital relay algorithm is developed to extract fundamental frequency components. These components are then used to calculate the impedance as seen from the relay location of a transmission line. The method is offline tested using realistic relaying signals of a 230 kV three-phase transmission line, and the results are compared with those of an algorithm based on Haar functions. The proposed algorithm is computationally simple and flexible to use with any sampling frequency.     

A Kalman filter based digital percentage differential and groundfault relay for a 3-phase power transformer

The design and real-time implementation of a Kalman-filter-based digital percentage differential and a ground-fault protection scheme for three-phase power transformers are presented. A set of eleven-state Kalman filters is used to estimate the fundamental and up to fifth harmonic components of the transformer current signals. The protective relay is equipped with an even harmonic restraint during magnetizing inrush conditions and a fifth harmonic restraint during overexcitation conditions. The restraint during external faults is provided by means of a percentage differential characteristic. The relay operates in half a cycle during internal faults. In order to achieve sensitive ground-fault protection, separate primary and secondary ground-fault protection are provided. The relay algorithm is implemented on a single TMS320 digital signal processor and tested in real time using a three-phase laboratory power transformer     

配电网接地故障特征及其诊断定位方法

快速、准确的故障定位是迅速隔离故障和恢复供电的前提,对于维护配电网的安全运行具有重要意义,而配电网的单相接地故障定位长期以来是难以解决的课题.本文通过对国内外关于各种研究情况做了全面深入地分析,在此基础上从接地故障测距算法和在线监测两方面进行了研究,并且针对基于对配电网发生单相接地故障后的故障主要特征的分析,提出了相应的接地故障定位系统以及硬件总体设计,对于提高供电配电网具有重要的研究意义和实用价值.     

Design and implementation of a digital differential relay for a3-phase power transformer based on Kalman filtering theory

The design and implementation of a digital differential relay for a three-phase power transformer based on Kalman filtering theory are presented. The differential current is modeled as a sum of a fundamental, second harmonic, and exponentially decaying DC component, plus a random noise of known variance. The fundamental and second harmonic components are optimally estimated using a five-state Kalman filter. Inrush and internal fault conditions are distinguished by the relative magnitudes of their differential currents. The algorithm is implemented on a TMS 320 digital signal processor and tested using a three-phase transformer. Results show that the relay provides good restraint for inrush conditions and the relay operation time for internal faults is less than half a cycle     

Advance Compensated Mho Relay Algorithm for a Transmission System with Shunt Flexible AC Transmission System Device

Abstract—The presence of shunt flexible AC transmission system devices adversely affect the performance of distance relay and create security and reliability issues. This article introduces a noble compensated Mho relay algorithm for the protection of transmission line employing shunt flexible AC transmission system devices, such as a static VAR compensator and static synchronous compensator. A detailed model of transmission system employing a shunt flexible AC transmission system device is explained. Then compensated impedance inserted by a shunt device in the transmission line is calculated, and finally, a compensated Mho relay algorithm is proposed to protect zone one of the transmission line. Simulation work is carried out in PSCAD/EMTP software. Results show that the proposed relay is secure, accurate, and reliable under the wide variation in power system parameters, such as load angle, fault resistance, fault location, and compensation level.     

基于分布参数模型的双端非同步故障测距算法

基于线路分布参数模型,提出一种双端非同步故障测距算法。该算法根据电路叠加原理,将故障后的网络等效为正常状态网络和故障分量网络的叠加,然后以单相系统为例,以故障距离和非同步时间作为未知数,对正常电流电压相量和故障分量分别建立测距方程组,推导出故障距离的解析表达式,并给出了伪根的识别方法。文章还分析了该算法对三相系统的适用性。仿真结果表明,该算法消除了非同步时间的影响,适用于各种故障类型,无需选相,计算量小,测距精度高,较好地解决了双端测距中的数据不同步问题。     

Fuzzy-neuro approach to fault classification for transmission lineprotection

This paper presents a new approach to real-time fault detection and classification in power transmission systems by using fuzzy-neuro techniques. The integration with neural network technology enhances fuzzy logic systems on learning capabilities. The symmetrical components in combination with three line currents are utilized to detect fault types such as single line-to ground, line-to-line, double line-to-ground and three line-to-ground, and then to define the faulty line. Computer simulation results are shown in this paper and they indicate this approach can be used as an effective tool for high speed digital relaying, as the correct detection is achieved in less than 10 ms