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 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     

Charge comparison protection of transmission lines-relayingconcepts

The authors describe the relaying concepts of charge comparison. Charge comparison is a new transmission line protection system. It is a form of current differential relaying. Charge comparison largely resolves the traditional problems of current differential relaying of transmission lines, which are that protection is lost if a channel fails, a large channel capacity is required, and precise channel delay compensation is required. This technique is suitable for the protection of two- or three-terminal AC transmission lines, of all lengths and voltage levels, with or without series of shunt compensation, with three-hole or single-pole tripping     

Adaptive transmission relaying concepts for improved performance

Concepts for adaptive protective relaying of transmission lines are presented. These include changes in online relay settings, relay characteristics, or logic in response to power system or environmental changes, or as a result of operating experience. Such changes as line-out or generator-out contingencies, which affect fault current distributions and degrade the system's security level, initiate adaptive protection system responses. Adaptive relaying is shown to be capable of improving relaying reliability and power system security and of achieving better utilization of transmission facilities. Most of the concepts require a hierarchical computer system, involving front-line parallel processors, a substation host, and remote central processors, all linked by channels that transmit data or relaying changes prior to or after a disturbance. It is suggested that maximum value from adaptive relaying will result from integration with existing or planned substation control and data acquisition functions and interfacing with the central energy management system (EMS). Emphasis is placed on use of interim hardware approaches to allow evolutionary development     

An adaptive scheme for parallel-line distance protection

This paper describes an adaptive protective relaying scheme for parallel-line distance protection. The scheme adjusts its operation based on the availability of input signals to achieve an optimal distance protection performance on parallel transmission lines influenced by the mutual coupling effect. When available, zero sequence current from the parallel line is used to fully compensate the mutual coupling effect. The zero sequence current ratio is used to avoid possible false operations on healthy lines, which may result from such compensation. When the parallel line's zero sequence current is not available, the line operating status is used instead to select the proper zero sequence current compensation factors in impedance calculation. Default zero sequence current compensation factor is used when both the parallel line's zero sequence current and line operating status signals are not available. The performance of the scheme has been verified on a simulated network and the results are presented     

Under-Reach Correction in Twin Circuits Without Residual Current Input From the Parallel Line

Mutual coupling poses difficult problems witnessed during single phase to earth fault, in transmission line protection. In parallel lines on the same right of way, mutually coupled zero-sequence circuits cause error in the apparent impedance seen by the relay. This causes the distance relay at one end of the faulty line to over-reach while the one at the other end to under-reach. Incorrect sensing of the ground fault due to zero-sequence voltage inversion caused by mutually coupled zero-sequence network may lead to false trip of the neighbouring healthy line. The paper develops characteristic expressions for effective sequence impedances of twin circuit lines and presents a non-iterative microprocessor based algorithm for fault distance and under-reach estimation in real time, for under-reach correction in basic distance relaying scheme. The residual current measurement from the parallel circuit is not required for this purpose.      

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.     

Charge comparison protection of transmission lines-communicationsconcepts

The authors present the basic concepts of a digital approach to the communications requirements of a new transmission line protection scheme. Charge comparison is a new transmission line protection system. It compares local and remote quantities of charge, using a bidirectional communications channel. Charge comparison is a form of current differential relaying. Traditional current differential relaying schemes have three critical communications-related problems: protection is lost if the channel fails, a large channel capacity is required, and precise channel delay compensation is required. In large measure, charge comparison overcomes these three communications-related problems     

超高压线路串补电容的微机保护算法

在超高压输电线路系统中,串联电容补偿具有提高输送容量和改善系统稳定性等优点,但由于串补电容的存在导致输电线路继电保护存在一系列问题。根据串补电容对距离保护和零序方向保护影响的理论分析,提出了基于TCSC串补电容的线路微机保护算法。算法利用TCSC的运行参数,考虑了串补电容在暂态过程以及电容运行状态对保护参数整定的影响,以避免TCSC使保护拒动或误动。最后通过仿真运行表明,该算法对于带有不同运行状态的TCSC的输电线路有很强的适应力和可靠性,可以满足线路继电保护的基本要求。     

Fault classification and location using HS-transform and radial basis function neural network

A new approach for protection of transmission lines has been presented in this paper. The proposed technique consists of preprocessing the fault current and voltage signal sample using hyperbolic S-transform (HS-transform) to yield the change in energy and standard deviation at the appropriate window variation. After extracting these two features, a decision of fault or no-fault on any phase or multiple phases of the transmission line is detected, classified, and its distance to the relaying point found out using radial basis function neural network (RBFNN) with recursive least square (RLS) algorithm. The ground detection is done by a proposed indicator ‘index’. As HS-transform is very less sensitive to noise compared to wavelet transform, the proposed method provides very accurate and robust relaying scheme for distance protection.     

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.     

Recursive functional expansion technique for computer-based impedance and differential protection

The development of a recursive functional expansion algorithm for extracting the desired frequency components from transient power system relaying signals is presented. The applications of this algorithm to impedance detection in transmission line protection and to harmonic restraint in transformer differential protection are discussed. The recursive algorithm generates fast fault detection timings for transmission lines and does not have restrictions on sample rate, data window or spacing of samples with respect to time. For power transformer differential protection, the combined second- and fifth-harmonic amplitude of the differential current is compared with the fundamental amplitude to arrive at a trip decision.     

Intelligent relaying scheme for series-compensated double circuit lines using phase angle of differential impedance

The paper presents a comprehensive intelligent relaying scheme using phase angle of differential impedance (PAODI) for series compensated double circuit transmission lines. The differential impedance (DI) is the ratio of differential voltage phasors of any phase across two ends of the transmission line to the differential current phasors of the same phase of the same transmission line. The PAODI of each phase are used as inputs to the data mining model known as decision tree (DT) to generate final relaying decision to identify the faulty phase(s) involved. The proposed scheme is extensively validated for different fault scenarios including inter-circuit and cross-country faults on the series-compensated parallel transmission developed on Real Time Digital Simulator (RTDS) platform. The test results obtained indicate that the proposed PAODI based intelligent relaying scheme is both dependable and secure in protecting series compensated double circuit transmission lines with a response time of less than 1 and 1/2 cycles.     

Ultra-high-speed directional protection of transmission lines using mathematical morphology

This paper presents a novel ultra-high-speed directional protection scheme developed using mathematical morphology (MM). The MM technique proposed is used to extract transient features from fault-generated voltage and current wave signals propagating along transmission lines during a post-fault period. Fault direction is determined by two composite relaying signals which are composed of the extracted transient features. A variety of fault scenarios has been simulated to evaluate the validity of the proposed scheme.     

音频接口与继电保护配合的探讨

大量的超高压线路以纵联保护为主保护,而音频接口是联系纵联保护与各种复用通道的纽带,对于确保线路保护的正确动作起着重要作用。探讨音频拉号继电保护的配合问题对提高电力系统继电保护运行的可靠性具有重要意义。作者根据继电保护现场运行经验,讨论了目前音频接口与继电保护的配合接线及保护配置上存在的一些问题。同时对纵联保护故障启动元件启动音频接口切断话音的拉发线、纵联保护与音频接口的配合中断器跳闸位置和其他保护动作发跳频、弱馈线路全线速动以及音频接口与其他保护动作发跳频、弱馈线路全线速动音频接口与微机保护连接中的特殊问题进行了探讨,并提出了相应的解决办法。     

High-Resistance Faults on Two Terminal Parallel Transmission Line: Analysis, Simulation Studies, and an Adaptive Distance Relaying Scheme

Performance of conventional nonpilot distance relay is affected by ground fault resistance, prefault system conditions, mutual effects of parallel lines and shunt capacitance influences. The work presented in this paper addresses the problems encountered by conventional non pilot distance relay when protecting two terminal parallel transmission lines. One of the key points of this paper is the detailed analysis of the apparent impedance as seen from the relaying point taking into account the effects of transmission line parameter uncertainties, mutual effects of parallel lines for simple and more complex configuration, shunt capacitance influences and variations in the system external to the protected line. Based on extensive computer simulations of the infeed/outfeed, fault resistance, mutual coupling and shunt capacitance effects on the relay characteristics, an adaptive digital distance relaying scheme is proposed using radial basis function neural network which provides more efficient approach for training, computation, adaptation and tripping than the conventional feed forward network using back propagation algorithm. In addition, the proposed adaptive scheme improves the performance of distance relay for double-circuit lines using modified compensation factor. Moreover, the scheme does not require separate communication channel for data transmission. The results of computer simulation show the improvement of sensitivity and selectivity of the relay     

同廊道交直流输电线路带电作业安全防护研究

超/特高压交直流并行线路带电作业区域电压高、场强大,为保证并行线路带电作业的安全开展,需要对 带电作业人员安全防护进行研究。分析了带电作业的安全影响因素,依据线路实际尺寸建立了1∶1计算模型, 采用有限元法对同走廊四回并行线路进行了电场仿真,获得了带电作业典型位置点的电场强度,根据仿真结果 对带电作业人员电位转移放电能量进行了计算。同时建立了人体模型,计算分析了等电位作业工况下人体不同 部位的电场强度特点。计算结果表明：同电压等级独立走廊带电作业安全防护措施同样适合于四回并行线路带 电作业。提出了相应的安全防护措施,研究结果可为同走廊多回并行线路带电作业的开展提供依据和技术支撑 。     

A novel approach using a FIRANN for fault detection and direction estimation for high-voltage transmission lines

This paper presents a novel approach to fault detection, faulted phase selection, and direction estimation based on artificial neural networks (ANNs). The suggested approach uses the finite impulse response artificial neural network (FIRANN) with the same structure and parameters in each relaying location. Our main objective in this work is to find a fast relay design with a detection time not dependent on fault conditions (i.e., current transformer saturation, dynamic arcing faults, short-circuit level, and system topology) and that uses only unfiltered voltage and current samples at 2 kHz. The suggested relay, which we have named FIRANN-DSDST, is composed of a FIRANN together with post-processing elements. The FIRANN is trained globally using training patterns from more than one relaying position in order to be as general as possible. The FIRANN is trained using an improved training algorithm, which depends on a new synaptic weights updating method, which we have named the mixed updating technique. The proposed relay is trained using training patterns created by simulating a real 400-kV network from the Spanish transmission network (REE). Finally, the proposed relay is tested using simulated and real fault data. The results encourage the use of this technology in a protective relaying field.     

多Agent技术在多端线路保护系统中的应用

针对传统的输电线路继电保护所存在的不足,提出了Agent技术在T接线路保护中的应用方案,阐述了该保护系统的结构和决策过程。Agent可以由一个人、一些软件或智能系统构成,具有自治、协调和分布等特性。仿真结果表明,与传统的距离保护和纵联保护相比,该保护系统具有能够实现全线速动和不需要专用通信通道的优点。     

Power system fault detection and state estimation using Kalmanfilter with hypothesis testing

An algorithm for detecting power system faults and estimating the pre and post-fault steady state values of the voltages and currents is described. The proposed algorithm is based on the Kalman filter and hypothesis testing. It is shown that a power system fault is ideally suited for single sample hypothesis testing. The performance of the proposed technique is examined in connection with the protection of parallel transmission lines. The proposed technique avoids many problems of parallel line protection. The simplicity and the avoidance of complicated software and hardware in addition to the stability of the relay under different switching conditions are some of the features of the proposed technique. Studies performed on a long double-circuit transmission line with and without series compensation show a trip time in all cases of around 5 ms