Performance assessment and control of power system relaying

The author outlines various reliability assessment and performance monitoring methods for power system protection. Particular reference is made to the approach adopted for protection performance assessment and control in China Light & Power Company Ltd. because of the special `operation when needed' nature of protection relaying, a probabilistic approach for reliability assessment is adopted with particular emphasis on dependability and security. Various statistical indices are utilized to illustrate the protection equipment performance from the power system and individual relay points of view. It is shown that the method of cause analysis for protection against incorrect operations can pinpoint problem areas for further managerial actions     

Adaptive relaying. A new direction in power system protection

The authors describe adaptive relaying, a new philosophy in protecting electric power systems. Adaptive relaying utilizes the continuously changing status of the power system as the basis for online adjustment of the power system relay settings. Consequently, it provides the required flexibility for obtaining very high levels of power system reliability. Digital relays with adequate software and communication capability make these devices ideal for implementing adaptive relaying concepts     

Online applications of wavelet transforms to power system relaying

Power system disturbances are normally subjected to transients and nonperiodic components which present a problem to the overall performance of protective relays. The use of traditional discrete Fourier transforms (DFTs) to extract the fundamental frequency components from the relaying signals is inappropriate to nonperiodic signals. A novel wavelet transform-based technique for power system relaying has been presented before, which has the ability to perform local analysis of relaying signals without losing the time-frequency information in the signal. This technique is considered to be straight-forward, fast, and adequate for online applications. In this paper, the theoretical background of the technique is presented. Then, the proposed method is described in detail. Finally, the effect of different parameters on the algorithm are examined in order to highlight its performance. It is found that the DWT is an excellent online tool for protective relaying applications using short data windows.     

Anatomy of power system blackouts: preventive relaying strategies

Major blackouts of electric power systems in which many customers are left without power are rare events. However, the effects of blackouts, for instance, can be catastrophic. It has been observed that protective system failures are a contributing factor in a large proportion of these blackouts. The most troublesome protection system failures are hidden failures, which remain dormant during normal system conditions, and are exposed during system disturbances. A study of hidden failures of the protective systems is undertaken to uncover their modes of failures, and to determine means of supervising their actions in times of highly stressed power system operations. The main contribution of this paper is to develop and document a method of quantitative analysis of the significance of hidden failures of protection systems. A complete protection system was designed for the New England 39-bus system and the hidden failure modes were used to develop regions of vulnerability and a vulnerability index. Through this analysis, critical protection systems, whose hidden failures would have a major impact on cascading failures or blackouts of the power system, can be identified These protection systems are candidates for increased monitoring and control, which would help alleviate the problems posed by hidden failures     

高压电源快切对企业电网继电保护影响的研究

高压快切装置在电源切换时,会对系统产生冲击包括低电压和冲击电流,如冲击过大可能引起继电保护动作,造成切换失败.本文对电源切换过程进行了理论研究,给出了母线残压和冲击电流的数学表达式,分析了切换可能引起误动的保护的类型及其原因,同时提出了快切装置和继电保护配合的措施,可以有效减小电源切换冲击,防止继电保护误动,提高切换成功率,保证负荷供电可靠性,并以实际系统为例进行了仿真验证.     

Combined fuzzy-logic wavelet-based fault classification technique for power system relaying

This paper presents a new approach to real-time fault classification in power transmission systems using fuzzy-logic-based multicriteria approach. Only the three line currents are utilized to detect fault types such as LG, LL, and LLG, and then to define the faulty line. An online wavelet-based preprocessor stage is used with data window of ten samples (based on 4.5-kHz sampling rate and 50-Hz power frequency). The multicriteria algorithm is developed based on fuzzy sets for the decision-making part of the scheme. Computer simulation has been conducted using EMTP programs. Results are shown and they indicate that this approach can be used as an effective tool for high-speed digital relaying, as the correct detection is achieved in less than half a cycle and that computational burden is much simpler than the recently postulated fault classification techniques.     

自适应控制在电力系统继电保护中的应用

继电保护需要适应频繁变化的电力系统运行方式,正确切除发生各种故障的设备,而自适应控制能在参数变化时保持系统的标准特性因此,可形成以自适应方式控制的继电保护－自适应保护。为此,介绍了自适应控制系统的模型,并以距离保护为例,说明运用自适应控制解决继电保护整定值设置和调整等问题的方法,给出自适应距离保护模型。     

A novel fuzzy-logic-based phase selection technique for power system relaying

Fast tripping and consequent single-pole auto-reclosure of the faulted phase for single-phase earth faults is extensively used in long line applications. Traditional phase selection techniques can suffer some drawbacks due to their dependency on varying system and fault conditions. However, with the advent of fuzzy-logic techniques, and their ability to map complex and non-linear power system configurations provide a very attractive solution to accurate and fast phase selection procedure. This paper presents a new approach to real-time phase selection in power transmission systems using fuzzy-logic-based multi-criteria approach. Only the three line currents are utilised to detect the faulted phase. An online wavelet-based pre-processor stage [IEEE Trans. Power Delivery, 18 (4) (2003) 1158; IEEE Trans. Power delivery 17(4) (2002) 908; IEEE Trans. Power Delivery, 18 (1) (2003) 170; Paper # 01TD069, IEEE T&D Conference, 28 October–2 November 2001, Atlanta, GA] is used with 10 samples data window (based on 4.5 kHz sampling rate and 50 Hz power frequency). The paper demonstrates the multi-criteria algorithm that is based on fuzzy sets for the decision making part of the scheme. Computer simulation have been conducted using EMTP programs. Results proved that the correct detection is achieved in less than half a cycle and that computational burden is simpler than the recently postulated phase selection techniques, and this approach can be used as an effective tool for high speed digital relaying.     

Adaptive transmission system relaying

The use of digital techniques to adapt transmission system protection and control to real-time power system changes is investigated. The discussion covers transmission system protection philosophy, transmission line protection, relay settings, transformer protection, and automatic reclosing. The tradeoff between dependability and security is examined, as well as the various conflicting criteria embodied in transmission line protection. Adaptive strategies that minimize the compromises required and thereby optimize system performance are presented     

Fuzzy logic-based relaying for large power transformer protection

Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. The frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. Then, traditional approaches will likely be maloperated in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.     

电网中谐波对继电保护的影响分析

分析了谐波对不同类型的继电保护装置的影响进行了理论分析,确保电力系统运行的稳定性。     

高压直流保护系统配置探讨

本文详细的阐述了以SIEMENS技术为平台的直流保护系统,并深入分析了常规直流保护系统和特高压直流保护系统的配置相同点和不同点。     

Computer assisted medical interventions

Many medical or surgical interventions can benefit from the use of computers. Through progress of technology and growing consciousness of the possibilities of real clinical improvements with computers, what was in the past the privilege of very few operations (mostly stereotactic neurosurgery) is now entering many surgical specialities. Although many technical issues remain to be solved, there is virtually no limit to the introduction of computers and robots in any surgical speciality. This tendency can take on the most varied forms. At the authors' institute, three golden rules have guided the computer assisted medical interventions (CAMI) project for about ten years: 1) conceive systems for which the clinical value is well defined; 2) develop generic tools that can be applied to many different clinical applications; and 3) provide efficient collaboration between the surgeon and the system through simple interfaces     

Machine learning for power system protection and control

Since the power system is undergoing a transition into a more flexible and complex system, it urges improvements in fault diagnosis techniques for the power system protection to avoid cascading damages at the occurrence of faults. Facing with challenges of massive data, several machine-learning based methods for identifying faults were proposed over the past years. In this paper, an overview of conventional and trending machine learning applications for the fault diagnosis are summarized.     

Protective relaying an medium- and high-voltage system

For this article we reviewed unusual outages, such as nonselective device operations during a fault, at different petroleum industry facilities. We found that changing some types of protective devices and modifying device settings improved both reliability and on-line performance. The following categories of protection problems were reviewed: ground faults on 12 kV feeders; ground faults on 4 kV motor feeders; faults on 115 kV transmission lines; and overexcitation of equipment. Each case is presented with: a brief synopsis of the problem encountered; our evaluation of the problem, including suggested solutions; and the “lessons to be learned” and trouble spots to avoid     

Reinforcement learning based backstepping control of power system oscillations

This paper proposes a reinforcement learning based backstepping control technique for damping oscillations in electric power systems using the generators excitation systems. Decentralized controllers are first designed using the backstepping technique. Then, reinforcement learning is used to tune the gains of these controllers to adapt to various operating conditions. Simulation results for a two area power system show that the proposed control technique provides better damping than (i) conventional power system stabilizers and (ii) backstepping fixed gain controllers.     

南瑞继保RS-9612线路保护装置在逆功率保护中的应用

1系统介绍 某厂电力外网进线采用双电源进线,分列运行的供电方式,母联开关正常时不投运.该厂自备电厂2#发电机受35kV变电站1#主变负荷限制(发电机不允许向厂外电网送电),1#主变的主要负荷为离子膜,当离子膜在运行中突然事故停电或大量降负荷时会造成逆功率方向保护动作跳闸,致使自备电厂10kⅦ段系统瓦解,迫使2#发电机停机.     

Frequency relaying based on instantaneous frequency measurement[power systems]

A frequency relay capable of under/over frequency and rate of change of frequency measurements has been implemented on a digital signal processor using an instantaneous frequency measuring algorithm. Careful attention to the filtering aspects of the relay is needed under dynamic conditions due to frequency modulation of the input signal. An algorithm for avoiding unwanted relay operation due to impulsive changes in the input signal is presented. Results are shown for simulated tests using computer-based relay testing equipment, and for overloads on a micromachine power system simulator     

基于多代理系统的继电保护

多代理(MAS)技术目前是分布式人工智能(DAI)发展的主要研究方向,它着重研究一组自治的、多个智能Agent之间的行为协调,适于解决传统AI和单一Agent所无法解决的复杂问题.该文把多Agent技术应用到输电线路的后备保护中,通过加强各智能体之间的配合与协调,从而达到在线路发生永久性故障时,能缩短后备保护动作时间的目的.     

基于Agent的继电保护数据传输系统

为了提高变电站自动化系统站内局域网通信中继电保护数据传输的实时性、有效性和灵活性，文章结合软件Agent技术，提出了一个应用于变电站站内局域网继电保护数据传输的Agent系统。它是基于多Agent的体系结构，包括3个子Agent。该系统具有主动探测并评估网络传输状况、进行数据分析，从而灵活调整传输策略的功能。实例系统的仿真结果表明，该系统可以有效地解决变电站继电保护信息传输中的各类数据流量冲突的问题，保障信息的可靠实时传输。