双回路接地距离保护的分析和整定

平行线路零序互感的存在,导致接地距离保护不能正确测量线路阻抗。在实际整定工作中,如何整定接地距离的补偿系数和可靠系数,整定规程没有给出具体的方法。分析了线路的实测阻抗,和高压电网在接地故障时电流分布的特点。基于不同系统运行方式,定性和定量地研究了零序互感对接地测量阻抗的影响,进而提出了接地距离保护一个简单实用的整定方法,具有普遍适用性。     

双回路接地距离保护的分析和整定

平行线路零序互感的存在,导致接地距离保护不能正确测量线路阻抗.在实际整定工作中,如何整定接地距离的补偿系数和可靠系数,整定规程没有给出具体的方法.分析了线路的实测阻抗,和高压电网在接地故障时电流分布的特点.基于不同系统运行方式,定性和定量地研究了零序互感对接地测量阻抗的影响,进而提出了接地距离保护一个简单实用的整定方法,具有普遍适用性.     

A novel fast distance relay for series compensated transmission lines

This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines.     

PMU based adaptive zone settingsof distance relays for protection ofmulti-terminal transmission lines

This paper proposes Phasor Measurement Unit (PMU) based adaptive zone settings of distance relays (PAZSD) methodology for protection of multi-terminal transmission lines (MTL). The PAZSD methodology employs current coefficients to adjust the zone settings of the relays during infeed situation. These coefficients are calculated in phasor data concentrator (PDC) at system protection center (SPC) using the current phasors obtained from PMUs. The functioning of the distance relays during infeed condition with and without the proposed methodology has been illustrated through a four-bus model implemented in PSCAD/EMTDC environment. Further, the performance of the proposed methodology has been validated in real-time, on a laboratory prototype of Extra High Voltage multi-terminal transmission lines (EHV MTL). The phasors are estimated in PMUs using NI cRIO-9063 chassis embedded with data acquisition sensors in conjunction with LabVIEW software. The simulation and hardware results prove the efficacy of the proposed methodology in enhancing the performance and reliability of conventional distance protection system in real-time EHV MTLs.     

Performance of distance relay mho elements on MOV-protectedseries-compensated transmission lines

It is shown that the applicability of memory-polarized distance relay mho elements to the protection of MOV (metal oxide varistor) protected series-compensated lines is dependent on the system configuration, line loading, the location of the potential source, and the magnitude of memory polarization. For a configuration with compensation at one end of a line, the results indicate certain advantages in using the potential from the line side of the capacitor, and the use of a relatively large magnitude of memory polarization. The presence of a conducting MOV enhances the performance of the mho element both in terms of security on reverse faults and dependability on forward faults. The results obtained pertain to the proposed application in the Ontario Hydro system of a relatively large amount of compensation at one terminal in each circuit of a double-circuit line     

Digital distance protection of transmission lines

Experience with a digital distance relay algorithm, which also utilizes a digital low-pass filter, is presented. It is shown that the relay is capable of tracking the apparent impedance of a transmission line, as it experiences a short circuit, with a speed and accuracy which are competitive with existing distance relay hardware. The distance relay algorithm is feasible with current large-scale integration technology, although a specific micro-processor architecture has not yet been directed to this particular application.     

Adaptive ground distance protection for UPFC compensated transmission lines: A formulation considering the fault resistance effect

This paper presents a mathematical deterministic adaptive distance protection formulation for UPFC compensated transmission lines. The proposed formulation is developed using a phase component approach and considers and compensates for various UPFC operation conditions and non-zero fault resistances. The proposed methodology is completely adaptive and independent of system characteristics (such as changes in transmission line impedances) or operating conditions (such as different load conditions and controlled reference parameters). Moreover, the proposed formulation uses local and remote end voltage and current signals as input data. The comparative test results demonstrate potential beneficial aspects of the proposed formulation for real-time applications.     

Modern approaches for protection of series compensated transmission lines

Series compensation has been employed to improve power transfer in long-distance transmission systems worldwide. However, this in turn introduces problems in conventional distance protection. The complex variation of line impedance is accentuated, as the capacitor's own protection equipment operates randomly under fault conditions. This paper proposes two approaches based on travelling waves and artificial neural networks (ANN) for fault type classification and faulted phase selection of series compensated transmission lines.A modal transformation technique, which decomposes the three-phase line into three single-phase lines, is used for this purpose. Algorithms based on two different modal transformations are developed for phase selection and fault classification. Each algorithm is derived from a corresponding truth table. The truth tables are constructed for different types of faults with different faulted phases and different transformation bases.The proposed ANN topology is composed of two levels of neural networks:

• In level-1, a neural network (ANN_F) is used to detect the fault. In level-2, four neural networks (ANN_A, ANN_B, ANN_C and ANN_G) are used to identify faulted phase(s), and activated by the output of ANN_F if there is a fault.
• System simulation and test results, which are presented and analyzed in this paper indicate the feasibility of using travelling waves and ANN in the protection of series compensated transmission lines.

     

IEEE/PSRC working group report on considerations in settinginstantaneous overcurrent relays on transmission lines

Setting instantaneous overcurrent (IOC) relays on subtransmission lines has not been considered a complicated procedure by most utilities. However, undesirable operations have drawn attention to their intended function and application. This report addresses the causes for erroneous instantaneous overcurrent relay settings to help protection personnel avoid future undesirable operations     

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。     

基于小波变换的串补输电线路故障选相研究

串补电容及其保护装置MOV的应用给常规的故障定位与选相方法带来了困难.然而,串补输电线路发生故障后以及故障期间MOV导通时将产生高频暂态电流行波,故障相和非故障相的暂态电流信号的大小及所合有的频率成分不同.本文采用小波分析方法,选择适当的小波函数与变换尺度对相电流进行小波变换,根据故障相和非故障相的暂态电流在此尺度上小波系数能量的差别,形成故障选相判据.大量的EMTP仿真结果证实了该方法的有效性.所提出的方法对串补超高压输电线路的故障定位与保护具有实际意义.     

基于小波变换的串补输电线路故障选相研究

串补电容及其保护装置MOV的应用给常规的故障定位与选相方法带来了困难。然而,串补输电线路发生故障后以及故障期间MOV导通时将产生高频暂态电流行波,故障相和非故障相的暂态电流信号的大小及所含有的频率成分不同。本文采用小波分析方法,选择适当的小波函数与变换尺度对相电流进行小波变换,根据故障相和非故障相的暂态电流在此尺度上小波系数能量的差别,形成故障选相判据。大量的EMTP仿真结果证实了该方法的有效性。所提出的方法对串补超高压输电线路的故障定位与保护具有实际意义。     

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     

A novel fast distance relay for long transmission lines

The measuring accuracy and the measurement stability of conventional distance relay will be influenced by complex and remarkable harmonic components due to the large capacitance of the line when it is used for a long line. Correspondingly, the tripping speed will be delayed to some extent. To solve this problem, a fast distance relay for long transmission lines is presented, which is on the basis of the differential equation algorithm using π transmission line model and the theory of Equal Transfer Process of Transmission Lines (ETPTL). The shortcomings of π model differential equation algorithm due to the impact of high frequency components can be overcome by using a low-pass filter. The problem resulting from the difference between the transfer feature of the voltages used by the distance protection and that of the currents due to the transient characteristic of coupling capacitor voltage transformers (CCVT) can be solved by using virtual digital CCVT. Then, the new distance relay can trip quickly by re-structuring the voltage at the fault point and iterative calculations. A variety of ATP simulation tests show that the new relay has fast tripping speed and high reliability when applied to the long transmission lines.     

Effects of VSC based HVDC system on distance protection of transmission lines

The priority to reactive power contribution from the Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) connection to support the grid during faults as suggested by the modern Network Code (NC) for HVDC affects the distance protection of transmission lines. Moreover, suppressing the negative sequence current during an unbalanced condition also interferes with the proper operation of the distance relays. This is because the current contribution from the converter is limited in magnitude and modified in the waveform in order to protect the power electronic devices during the fault in comparison to the synchronous generator fault current characteristics. This paper discusses the cause as well as the severity of the problems faced by the distance protection of transmission lines connected to the VSC based HVDC system by analyzing the apparent impedance analytically and in the simulation. The response of the relay to balanced and unbalanced faults lying on transmission lines is investigated. It is shown that the VSC limited reactive support and suppressed negative sequence current affect fault detection, forcing the relay to malfunction. The results of this paper can be used as a reference for understanding the effects of VSC-HVDC system on the operation of the distance protection during faults.     

Fast orthogonal search approach for distance protection of transmission lines

A distance protection scheme for transmission lines based on analyzing the measured voltage and current signals at the relay location using fast orthogonal search (FOS) is presented in this paper. FOS has the ability to accurately provide fast estimate of the voltage and current fundamental frequency phasors that are required for a digital distance relay. Compared to the conventional FFT, FOS can estimate the fundamental phasors with higher accuracy and less number of samples. The proposed scheme has been tested on a transmission line model to verify the merit of this approach. The tests presented include solid ground faults, phase faults, and high impedance faults at different fault locations and loading conditions. The proposed scheme can classify all fault cases in less than one cycle after the inception of the faults.     

一种同杆并架双回线接地距离保护方案

距离保护应用于同杆并架双回线时其动作性能受零序互感的影响.通过对同杆并架双回线接地故障时零序电流特点以及零序互感对接地距离保护影响的分析,指出两回线零序电流反向是同杆并架双回线接地距离保护误动的主要原因,根据两回线零序电流反向时,故障线路的零序电流大于非故障线路,提出了一种逻辑判断的零序电流补偿方法.数字仿真的结果表明,该方法提高了同杆并架双回线距离保护的性能.     

An adaptive protection scheme for advanced series compensated (ASC)transmission lines

This paper presents an adaptive protection scheme for advanced series compensated (ASC) transmission lines. The scheme is based on Kalman and adaptive Kalman filters. The adaptive scheme utilizes the differences in the transient current signals for faults encountering and not encountering the ASC to determine the fault location with respect to the ASC and the faulted phases. Equations to determine the line impedance to the fault on these lines are developed. The adaptive scheme is tested for faults along and outside the protected line using EMTP simulated data     

A performance oriented impedance based fault location algorithm for series compensated transmission lines

This paper proposes a performance oriented fault location algorithm for series compensated transmission lines. The algorithm estimates the fault location based on the calculated fault voltage and current using two end measurements and line parameters. Fault location computations are carried out considering faults existed before or after the compensator location on the line. The calculated MOV impedance is the key factor in determining whether or not the fault is located in front of the compensator. A 380 kV transmission line with a series capacitor and an MOV has been tested for various fault types, fault locations and fault resistances. The results show that the algorithm accurately estimates the fault location for all cases.     

Stochastic evaluation of transient recovery voltages across circuitbreakers of series capacitor compensated transmission lines

This paper presents a Monte Carlo based approach to evaluate the maximum transient recovery voltages induced across circuit breaker poles during clearing a fault on a series capacitor compensated transmission line. In this context, investigations have been conducted on a sample power system model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. A risk index that reflects the likelihood that the transient recovery voltage induced across circuit breaker poles exceeds its design value is also presented