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     

A recursive least-squares digital distance relaying algorithm

A new digital distance relaying algorithm based on the well-known theory of least-squares is developed, and the results of testing it using numerical simulation are presented. The new technique estimates the distance to the fault and the fault resistance. To minimize the computational requirements of the digital relay, a recursive least-squares approach is used. Computer simulation results of the new least-squares algorithm seem promising, indicating that it should be considered for further testing and evaluation     

Fast harmonic computation for digital relaying

It has been shown that the fast Fourier transform of a sequence which slides over a time-limited rectangular window can be carried out in a nonrecursive manner by means of O(N) computations. The same idea is applied in this paper to the digital relaying field, where only certain isolated harmonics, rather than the full spectrum, are needed, leading to O(log₂N) computations per harmonic. The particular case N=16 has been used for comparison purposes, showing that the new technique is less expensive than other nonrecursive algorithms in the literature     

Fast digital distance algorithm using FIR filtering

In digital transmission line distance protection schemes based on microprocessors, the post-fault data window required to cope with transient signal components forms the major part of the total relaying time. As a result, short relaying times and accurate impedance calculations are difficult to achieve when the signals have substantial transient components. This paper establishes that a simple series R-L model of the transmission line is an adequate basis for many practical cases. Based on an analysis of an impedance calculation method using an R-L model, a digital filtering technique is proposed which requires a very short time window and little computation. The algorithm is therefore suitable for microprocessor implementation. Laboratory test results are included.     

A novel digital distance relaying technique for transmission lineprotection

Parallel transmission lines often pose more difficult protection problems than single lines. In the case of parallel lines, a number of problems arise when using the distance protection. The paper discusses problems associated with parallel line distance relaying schemes and presents a novel technique to overcome these problems. Two relays instead of four are proposed for the double lines, One relay is located at the beginning and another one at the end. Each relay is fed by three voltage and six current signals from the two lines. The suggested technique is based on the comparison of the measured impedance of corresponding phases. So, the complexity of the possible types of faults, high path fault resistance, mutual effects, current in-feed, inter-system faults are solved. Moreover, 100% of line is protected and the problem of balance-point locations is avoided. Alternative Transient Program models the power system and simulates different fault conditions     

A digital relaying algorithm for detecting transformer windingfaults

A digital algorithm for detecting faults in single-phase and three-phase power transformers is proposed. The algorithm is suitable regardless of whether it is possible to measure winding currents. The algorithm does not require B-H curve data. A variety of operating conditions simulated on a computer were used to test the algorithm. The results show that it performs well     

A recursive Newton type algorithm for digital frequency relaying

This paper presents a new recursive Newton type algorithm devoted to frequency relaying. The algorithm is designed from the nonrecursive Newton type algorithm and recursive least error squares algorithm. The frequency is estimated from the uniformly sampled voltage signal. The algorithm testing based on computer simulated and experimentally obtained data record processing confirmed the good features of the algorithm developed. Due to its computational efficiency, the algorithm is suitable for various real-time power system measurement applications.     

最小二乘法在距离保护中的应用初探

电压和电流信号中存在的非周期分量和高次谐波分量会影响到距离保护测量阻抗的真实性.通过滤除非工频信号而获得的基波阻抗值,可以确保距离保护动作的正确性.基于最小二乘原理的参数估计是应用相当普及的方法,将最小二乘法应用于距离保护中,构建了基于微分方程的系统模型,提出通过测量电感参数获得测量电抗,为解决基于微分方程测量电阻参数估计模型误差大的问题,提出基于有功功率概念构建的测量电阻参数估计模型,并就所提出方法进行了仿真验证,表明通过最小二乘法进行的测量阻抗参数估计是可以应用于距离保护的.     

最小二乘法在距离保护中的应用初探

电压和电流信号中存在的非周期分量和高次谐波分量会影响到距离保护测量阻抗的真实性。通过滤除非工频信号而获得的基波阻抗值,可以确保距离保护动作的正确性。基于最小二乘原理的参数估计是应用相当普及的方法,将最小二乘法应用于距离保护中,构建了基于微分方程的系统模型,提出通过测量电感参数获得测量电抗,为解决基于微分方程测量电阻参数估计模型误差大的问题,提出基于有功功率概念构建的测量电阻参数估计模型,并就所提出方法进行了仿真验证,表明通过最小二乘法进行的测量阻抗参数估计是可以应用于距离保护的。     

An accurate algorithm for high resistance earth-fault distance protection

High resistance earth faults cause errors in locating the fault distance owing to the back-feed effect and the relatively small fault current. This is aggravated for long lines when the capacitive line current is neglected. This paper presents an algorithm for accurate fault location by including the line capacitance in the circuit model. Tripping logic is based on consistency measurements of the line reactance to the fault. Accurate simulations were run to validate the algorithm, and the results show considerable improvement in accuracy over models that neglect the line capacitance.     

New algorithms for microprocessor-based distance relaying

System impedance calculation for distance relaying requires extraction of fundamental frequency components from highly distorted post-fault relaying signals. Many algorithms are available for extracting the fundamental frequency component, but most of them involve a large amount of computation, whilst others have low accuracy, or poor convergence, or both. This paper describes two algorithms based on the Hartley transform. They are computationally simple, have good frequency response and give fast convergence in the calculation of resistance and reactance. Their efficacy has been examined using representative voltage and current relaying signals. The results obtained and presented here are gratifying.     

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.     

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.     

Fundamental basis for distance relaying with parametricalestimation

This paper deals with the application of parametrical estimation to transmission line protection. A classification of several algorithms based on the line differential equation, is described. New algorithms are proposed and evaluated with transient simulations     

Numerical distance relaying algorithm based on Mathematical Morphology and Least-Squares Curve Fitting method

A new numerical distance relaying algorithm based on Mathematical Morphology and a Least-Square Curve Fitting has been proposed. It makes use of morphological operators to detect and classify the faults and a Curve Fitting method to estimate the fault distance. To show the effectiveness of the proposed technique, computer simulations have been carried out on a test system, considering several fault types in different locations, loading angle and fault incidence angle. Due to simple mathematics operations used, the protection scheme proposed displays secure and effective high speed fault detection and tripping.     

超级电容快速在线参数辨识及状态估计

传统的超级电容三支路RC等效电路模型在快速充放电过程中并不能很好地描述超级电容充放电特性,且三支路RC等效电路模型参数在线辨识困难。为了提高快速充放电工况下超级电容状态估计和参数辨识的准确性,提出了基于简化模型和EKF的状态估计和参数辨识方法。首先,通过对快速充放电工况下模型简化可行性分析,在满足精度要求的前提下将三支路RC模型简化为二支路RC模型;其次,将模型参数也作为状态变量加入到状态方程中,采用EKF算法实现超级电容状态量和模型参数的同时在线估计;最后,采用一节50 F的超级电容在恒流充电、恒电阻放电的工况下验证了所提方法的有效性。实验结果表明,基于简化模型的状态估计和参数辨识方法在不降低估计精度的情况下加快了估计速度。     

A simplified algorithm for digital distance protection based onFourier techniques

Algorithms for digital distance protection based on Fourier series techniques are examined. An approach based on a variable-frequency sampling technique is proposed. The algorithm is examined from a theoretical point of view, and its behavior is simulated under fault conditions typical of the Italian electrical network. The algorithm is shown to behave in the same way as other Fourier series-based algorithms and to have the advantage of reducing the computational burden     

配电线路全线速切继电保护技术

针对配电系统采用的分段式过流保护存在速段保护范围小、整定配合复杂等问题,研究并提出了一种配电线路全线速切保护系统.该系统基于纵联比较的保护原理,结合配电系统的保护配置特点,借助通信手段完成上下游保护之间的信息交换,为配电线路提供全线速动保护功能.依据所获取保护信息类型的不同和对信息利用方式的不同,提出了基于过流元件的闭锁式速切保护系统和基于低电流、低电压元件的允许式速切保护系统,研究了2种速切保护系统的逻辑构成和工作方式,并从快速性、安全可靠性、方案实现的难易程度等方面分析各自的特点.对速切保护所采用的通信方式进行了分析研究,对利用中间继电器、数传电台和光纤3种通信方式进行保护信息交换的延时进行了实验室测试.采用数传电台通信方式的闭锁式速切保护已经投入现场试运行,目前运行效果良好.     

An adaptive sampling-interval generator for digital relaying

A method for measuring frequency at a fixed sampling rate is described, and a variable-rate method is introduced. An algorithm based on a digital Fourier transform, which locks the sampling frequency in a microprocessor-based system to the fundamental of an incoming voltage waveform, is devised. The algorithm also intrinsically provides a measurement of the frequency. The algorithm is applied to the case of a volt/hertz relay     

基于Matlab的计算机距离保护微分方程算法仿真与研究

运用M atlab完成电力系统计算机距离保护的仿真,应用了两种基于线路模型的解微分方程的阻抗算法,分析了其应用于不同参数线路时的适应性,并通过分析在考虑存在干扰和误差时的阻抗计算结果,对两种算法的稳定性进行了研究。还对这两种算法的工程应用提出了有益的建议。