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.     

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.     

An Improved Pilot Relaying Scheme for Shunt Compensated Transmission Line Protection Based on Superimposed Reactive Power Coefficients

The fault component power and energy based relaying schemes have limitation during double-phase to ground fault due to the mutual coupling effect. This article presents a superimposed reactive power coefficient (SRPC) based pilot relaying scheme for the protection of shunt compensated transmission line. SRPC of a phase is defined as the ratio of integrated superimposed reactive power (SRP) of that phase to the maximum magnitude of integrated SRPs among all three phases. If SRPC of any phase is found less than ?0.5, an internal fault is detected and that phase is considered as a faulty phase. If no phase possesses SRPC less than ?0.5, the fault is an external fault. The algorithm will start only if the superimposed differential current of any phase is found more than 50% of pre-fault differential current. The results are obtained using PSCAD/EMTDC software for different conditions, such as different fault resistances, fault locations, static VAR compensator locations, and source impedances. The proposed scheme is found robust and accurate for all the cases considered. The performance of the proposed scheme is superior to the recently proposed similar type of scheme and is unaffected from capacitive coupled voltage transformer and current transformer measurement errors and synchronization error.     

Application of Haar functions for transmission line and transformer differential protection

The development of algorithms, based on Haar functions, for extracting the desired frequency components from transient power-system relaying signals is presented. The applications of these algorithms to impedance detection in transmission line protection and to harmonic restraint in transformer differential protection are discussed. For transmission line protection, three modes of application of the Haar algorithms are described: a full-cycle window algorithm, an approximate full-cycle window algorithm, and a half-cycle window algorithm. For power transformer differential protection, the combined second and fifth harmonic magnitude of the differential current is compared with that of fundamental to arrive at a trip decision. The proposed line protection algorithms are evaluated, under different fault conditions, using realistic relaying signals obtained from transient analysis conducted on a model 400 kV, 3-phase system. The transformer differential protection algorithms are also evaluated using a variety of simulated inrush and internal fault signals.     

Research on the protection coordination ofpermanent magnet synchronous generatorbased wind farms with low voltage ridethrough capability

This paper proposes a pattern recognition based differential spectral energy protection scheme for ac microgrids using a Fourier kernel based fast sparse time-frequency representation (SST or simply the sparse S-Transform). The average and differential current components are passed through a change detection filter, which senses the instant of fault inception and registers a change detection point (CDP). Subsequently, if CDP is registered for one or more phases, then half cycle data samples of the average and differential currents on either side of the CDP are passed through the proposed SST technique, which generates their respective spectral energies and a simple comparison between them detects the occurrence and type of the fault. The SST technique is also used to provide voltage and current phasors and the frequency during faults which is further utilized to estimate the fault location. The proposed technique as compared to conventional differential current protection scheme is quicker in fault detection and classification, which is least effected from bias setting, has a faster relay trip response (less than one cycle from fault incipient) and a better accuracy in fault location. The significance and accuracy of the proposed scheme have been verified extensively for faults in a standard microgrid system, subjected to a large number of operating conditions and the outputs vindicate it to be a potential candidate for real time applications     

基于高频暂态分量进行相关分析及模糊推理的选相新方法

提出一种利用故障分量中高频分量实现故障选相的新原理。该原理直接利用电流互感器饱和前传变的暂态高频电流,使用小波提取相应频段暂态信号特征,对提取的信号特征进行相关分析,使用模糊集合对相关系数的隶属度综合评判进行选相。用该原理实现的选相装置可以配合基于暂态量的单端保护使用,具有超高速的特点,且不受过渡电阻、故障初始角及系统振荡的影响。对于三相换位不完全造成模量不平衡的情况也能进行正确选相。对某典型500 kV线路进行各种故障类型仿真,取得了满意的效果。     

基于纵联比较原理的广域继电保护算法研究

提出了基于纵联比较原理的广域继电保护算法。该算法通过广域继电保护系统收集特定保护范围内各智能电子设备(IED)的故障方向信息,结合文中定义的IED动作系数AF和关联系数RF进行简单运算,即可确定出故障的位置。借鉴电力系统分析中的N?1原则,提出广域继电保护系统N个元件中的某一个元件失效时整个系统应仍能正确工作的N?1概念,分析了继电保护系统的N?1运行状况,提出了基于广域信息应对该运行状况的继电保护策略。算例分析表明:文中提出的广域继电保护算法原理简单、运算方便、判断结果准确,能较好地克服N?1运行状况带来的影响,可明显提高继电保护系统的性能。     

Modeling methodology and faultsimulation of distribution networksintegrated with inverter-based D

This paper proposes a pattern recognition based differential spectral energy protection scheme for ac microgrids using a Fourier kernel based fast sparse time-frequency representation (SST or simply the sparse S-Transform). The average and differential current components are passed through a change detection filter, which senses the instant of fault inception and registers a change detection point (CDP). Subsequently, if CDP is registered for one or more phases, then half cycle data samples of the average and differential currents on either side of the CDP are passed through the proposed SST technique, which generates their respective spectral energies and a simple comparison between them detects the occurrence and type of the fault. The SST technique is also used to provide voltage and current phasors and the frequency during faults which is further utilized to estimate the fault location. The proposed technique as compared to conventional differential current protection scheme is quicker in fault detection and classification, which is least effected from bias setting, has a faster relay trip response (less than one cycle from fault incipient) and a better accuracy in fault location. The significance and accuracy of the proposed scheme have been verified extensively for faults in a standard microgrid system, subjected to a large number of operating conditions and the outputs vindicate it to be a potential candidate for real time applications     

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.     

A rough membership neural network approach for fault classification in transmission lines

Objective: This paper presents a new approach for fault classification in extra high voltage (EHV) transmission line using a rough membership neural network (RMNN) classifier.Methods: Wavelet transform is used for the decomposition of measured current signals and for extraction of ten significant time–frequency domain features (TFDF), as well as three distinctive time domain features (TDF) particularly in terms of getting better classification performance. After extracting useful features from the measured signals, a decision of fault type of a transmission line is carried out using ten RMNN classifiers. Furthermore, to reduce the training times of the neural network, the rough neurons are used as input layer neurons, and the fuzzy neurons are utilized in hidden and output layer in each RMNN. And the Back Propagation (BP) algorithm is employed for determining the optimal connection weights between neurons of the different layers in the RMNN.Results and Conclusions: To verify the effectiveness of the proposed scheme, extensive simulations have been carried out under different fault conditions with wide variations in fault type, fault resistance, fault location and fault inception angle. Simulations results show that the proposed scheme is faster and more accurate than the back-propagation neural network (BPNN), and it is proved to be a robust classifier for digital protection.     

正序故障分量及其在继电保护中的应用

根据叠加原理给出正序故障分量的概念及特点．详细阐述正序故障分量在故障方向判别、相比较纵联保护、自适应电流保护及故障测距中的应用原理，对比说明基于正序故障分量的继电保护原理较传统保护所具有的优点。     

High‐speed directional relaying using adaptive neuro‐fuzzy inference system and fundamental component of currents

This paper proposes an adaptive neuro‐fuzzy approach for fault direction estimation in sectional transmission lines. The ANFIS (adaptive neuro‐fuzzy inference system) network is designed by selecting different input and output member functions and rules for training and testing of fault cases. The fundamental component of current obtained from three‐phase current employing discrete Fourier transform (DFT) is given as input to the ANFIS module. The trained ANFIS module is then tested for detecting the fault direction. The relay is located at middle section‐2, which is considered as the primary section to be protected. It takes section‐1 as reverse section and section‐3 as forward section. This method is not affected by the variation of fault type, fault inception angle, fault location, and fault resistance. The biggest advantage of the ANFIS method is that it can detect the fault direction within 1 ms in almost all cases, which is much less than the implemented distance relaying scheme. The second advantage of the method is that it takes less number of training samples to detect the direction accurately as compared to other training algorithms like ANN, SVM, etc. The third advantage of the proposed scheme is that it offers protection to 99% of line length in all the three sections. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

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.     

有源配电网电流差动保护应用技术探讨

有源配电网具有多电源、多分段、多分支、功率双向流动、弱馈等特征,传统三段式电流保护难以保证选择性和灵敏性,需要提供新的更有效的保护方法。基于该背景,将正序故障分量电流差动保护引入到有源配电网,探讨其应用原理与实现技术。针对不同的馈线结构,给出了适应性差动保护动作判据及门槛整定原则。针对配电网线路特点,提出并实现了基于故障信息的电流数据自同步方法。根据配电自动化通信体系最新进展,探讨了基于点对点对等通信实现差动保护数据交换的通信规约。基于智能配电终端平台,开发出正序故障分量电流差动保护样机并对其进行了综合测试,测试结果验证了所提保护方案的可行性。     

基于补偿电压的突变量方向判别原理

突变量理论广泛应用于电力系统的微机保护，文中充分利用正，反方向故障时补偿时压突变量与母线电压突变量的变化规律，提出了基于补偿电压的突变量方向判别原理，详细分析了该判据在各种不同运行工况下的动作特性，并指出了该保护判据的基本整定原理及尚需注意的问题，此外，文中还针对方向保护所遇到的一些特殊问题进行了详尽的分析。     

基于电流特征量相关系数的UHVDC线路高阻接地故障保护

特高压直流输电线路距离长、跨越区域复杂,故障发生率较高,常规电流差动保护的快速性较差且耐过渡电阻能力有限,为此提出一种基于电流特征量相关系数的线路高阻接地故障保护新原理。首先利用状态空间分析得到直流线路两端稳态电流时域表达式;随后,分析电流成分,发现其衰减振荡项中的角频率可反映线路对地故障,且可用相关系数衡量。接着利用两端电流和、电流差进一步突出角频率特征,并计算两者的相关系数构造判据特征量。在此基础上,根据判据特征量在区内外故障的不同特征,计及直流输电系统控制特性,提出了纵联保护新原理。该原理无需电容电流补偿,且对信道要求低,利于工程应用。仿真结果表明,该方案耐受过渡电阻能力和快速性优于常规电流差动保护。     

500kV继电保护故障信息处理系统动模试验方案

通过分析继电保护故障信息处理系统在保护与子站通信方式、保护信息的完整性、保护信息分类、通信规约和高级应用等方面存在的问题以及常规测试的局限性,提出了基于RTDS(realtimedigitalsimulation)的继电保护故障信息处理系统动模试验方案,通过该方案能很好地测试继电保护故障信息处理系统所提供保护信息的完整性、通信能力和各种高级应用功能。采用该方案在华东电力试验研究所对一些厂商的系统进行了测试,取得了较好的效果。     

基于电子式互感器的变压器励磁涌流识别方法

随着电子式互感器研究的日趋成熟及智能变电站的快速推进,智能变电站已广泛采用电子式互感器获取电流及电压信号。传统的变压器保护采用励磁涌流中的二次谐波含量区分励磁涌流和故障电流,从而对差动保护进行闭锁。但在空投或故障切除后恢复供电时,变压器内部发生轻微匝间故障,受非故障相励磁涌流的影响,差动保护可能延迟动作甚至拒动。针对上述原理的缺陷,提出了二次谐波“或”闭锁原理加故障开放的励磁涌流识别方法。试验结果表明,改进方案能明显提高变压器内部故障时差动保护的动作速度。     

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.     

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.