On-line fault diagnosis of power substation using connectionistexpert system

This paper proposes a new connectionist (or neural network) expert system for the online fault diagnosis of a power substation. The connectionist expert diagnosis system has similar profile to an expert system, but can be constructed much more easily from elemental samples. These samples associate the faults with their protective relays and breakers as well as the bus voltages and feeder currents. Through an elaborately designed structure, alarm signals are processed by different connectionist models. The output of the connectionist models is then integrated to provide fine final conclusion with a confidence level. The proposed approach has been practically verified by testing on a typical Taiwan Power (Taipower) secondary substation. The test results show that rapid and exactly correct diagnosis is obtained even for fault conditions involving multiple faults or failure operation of protective relays and circuit breakers. Moreover, the system can be transplanted into various substations with little additional implementation effort     

An Expert System for Fault Section Estimation Using Information from Protective Relays and Circuit Breakers

This paper deals with an expert system which can estimate possible fault sections using information from protective relays and circuit breakers. This system is applicable to dispatching centers and can help dispatchers to judge emergency situations as the first step in restoration procedures. When some faults occur, the system makes inferences based on both knowledge about protection systems and information on the operating protective relays and tripped circuit breakers. The system can give possible answers even in the case of multiple faults and false operations of relays and circuit breakers. This expert system is written in Prolog.     

A hybrid expert system for faulted section identification, faulttype classification and selection of fault location algorithms

The authors present an expert system developed in Turbo PROLOG to identify faulted sections and interpret protective apparatus operation in large interconnected power systems. This expert system is capable of identifying bus faults, line fault sections, and fault sections in the common area of a specific bus and line. Also, the expert system identifies relays or breaker malfunctions. The expert system is expanded to include real-time measurements of current and voltage phasors to classify the type of fault that the faulted section has experienced. When the faulted section is a transmission line, the expert system then selects an appropriate fault location algorithm to compute the fault location in miles. The importance of using a combination of numeric and database algorithms is emphasized     

Development of expert system for operation at substation

An expert system that offers support information in substation fault occurrence is described, focusing on a method for fault section estimation. This system edits fault information and estimates the fault section. With respect to the fault section. With respect to fault section estimation, a method that makes maximum use of sequential information on protective relay and circuit breaker operation even for complicated fault conditions involving multiple faults and incorrect operation or incorrect nonoperation of protective relays and circuit breakers. This system is undergoing field test in a commercial EHV substation, and so far normal operation is reported     

Fault Section Estimation of Power System Using Colored and Timed Petri Nets

A correct and rapid inference is required for practical use of expert system for fault section estimation in power systems. This paper proposes a new model-based expert system for fault section estimation using colored and timed Petri nets. The Petri nets simplify the inference procedure greatly because it can represent the causalities among faults of power system components, protective actions of relays and circuit breakers. They can also represent the operating states of these protective devices explicitly, or, more precisely, whether a relay has been actuated correctly or falsely, etc. In addition, time sequence information on actuated relays and tripped circuit breakers can be handled by using the colored and timed Petri nets. Therefore, the operating states of relays and circuit breakers can be inferred more correctly. Petri nets are suited for parallel processing so well that there is a possibility of reducing the inference time considerably. In the proposed system, the inference is executed by setting the initial states in the Petri nets using the information on the actuated relays and the tripped circuit breakers and then operating the Petri nets. There have been several test cases which used a prototype system on the Macintosh computer employing Object Common Lisp, and good results have been obtained.     

Development of an expert system for analyzing faults in power systems based on waveform recognition by artificial neural networks

In restoration of a power system, appropriate steps need to be taken in early stages to avoid damage to the public caused by insufficient power supply. The first step in the restoration is the analysis of the fault that has produced the power failure. Today, a large amount of data will be available at the occurrence of a fault due to the use of advanced communication systems using digital relays and optical fibers. Such systems are intended to obtain data from the relays and circuit breakers (CBs) under operation and the voltage and current during operation and the prefault and postfault periods. This paper presents a hybrid fault analyzing expert system using data based on protective devices and phasor measurement. This system is a combination of an artificial neural network (ANN) and an expert system (ES). The ANN is used to simplify the analysis of current and voltage waveforms, which is considered difficult due to the presence of a fault resistance and the line impedance. Since a fault waveforms contains various ambiguous factors depending on the nature of the fault resistance, load current and other system parameters, the use of ANN is effective making such determinations.     

故障信息处理系统中继电保护装置的可靠性研究

针对继电保护装置的工作特点拟定了继电保护装置可靠性的特征量。建立了继电保护装置可靠性的马尔可夫模型,运用状态空间法进行可靠性分析。最后提出了如何利用故障信息处理系统中大量丰富的信息实现继电保护装置可靠性分析的方法。     

A new neural networks approach to on-line fault section estimationusing information of protective relays and circuit breakers

This paper proposes a new neural network diagnostic system for online power system fault section estimation using information of relays and circuit breakers. This system has a similar profile of an expert system, but can be constructed much more easily from elemental samples. These samples associate fault section with its primary, local and/or remote protective relays and breakers. The diagnostic system can be applicable to the power system control center for single or multiple fault sections estimation, even in the cases of failure operation of relays and breakers, or error-existent data transmission. The proposed approach has been practically verified by testing on a model power system. The test results, although preliminary, suggest this system can be implemented by various electric utilities with relatively low customization effort     

A method for locating fault section by using sequential information at substations

This paper presents a new real-time method for locating fault section at substations. When a fault occurs, considerable information resulting from protective relay operation and circuit-breaker operation is recorded. Using this information an attempt is made to locate the fault section, especially by considering the sequential relationship of the information and by dividing fault areas. Primarily, in this method, the fault area is divided into several sections based on protection area and operation time of protective relays. Next, expecting subsequent operation of backup relays, the “waiting time” for reasoning is given to each divided section. After a lapse of “waiting time,” all the suspected fault sections are extracted and given priority based on the empirical knowledge of experts. A prototype of the expert system was developed for fault section location, which was applied to various complicated fault cases. The effectiveness of the method was proved even in case of multiple faults and no-operation of protective relays the circuit breakers.     

电力变压器保护设计专家系统的结构

提出了一个用于变压器保护辅助设计的专家系统，不仅可以实现保护系统配置、保护方式选 择、保护装置选型及继电器产品确定，还能表示保护设备之间、保护系统与一次系统之间的 关系。     

Agent-based self-healing protection system

This paper proposes an agent-based paradigm for self-healing protection systems. Numerical relays implemented with intelligent electronic devices are designed as a relay agent to perform a protective relaying function in cooperation with other relay agents. A graph-theory-based expert system, which can be integrated with supervisory control and a data acquisition system, has been developed to divide the power grid into primary and backup protection zones online and all relay agents are assigned to specific zones according to system topological configuration. In order to facilitate a more robust, less vulnerable protection system, predictive and corrective self-healing strategies are implemented as guideline regulations of the relay agent, and the relay agents within the same protection zone communicate and cooperate to detect, locate, and trip fault precisely with primary and backup protection. Performance of the proposed protection system has been simulated with cascading fault, failures in communication and protection units, and compared with a coordinated directional overcurrent protection system.     

Closed-loop testing with the real-time digital power system simulator

Most protection and control equipment is usually tested in the open-loop mode. However, closed-loop testing is often the only cost-effective approach. This paper highlights the areas where closed-loop testing of protective relays and control equipment is preferable. Test setups with a real-time digital simulator for closed-loop testing of protective relays, power system stabilizers, and controllers for controlled closing of individual poles of a shunt capacitor breaker are described.     

Performance of Generator protection during major system disturbances

Disturbance is an inherent part of any power system during the transition from one steady-state operating condition to the next. Protective relays may experience abnormal operating conditions during this transient period. This paper reviews various control actions that play a part during the transition and provides technical guidance to the industry on the application and setting of generator protective relays that can operate during major system disturbances.     

A novel approach for interactive protection system simulation

This paper presents a new approach for interactive power network protection system simulation. In the new approach, power system transients are simulated using an Electromagnetic Transients Program (EMTP), while protective relays can be modeled using any high-level language or commercially available software package, such as MATLAB. The interactions between power systems and relays are implemented by using an “interaction buffer”. Using this technique, the EMTP can be run in single-step, multiple-step or mixed mode. This new approach makes the protection system simulation quite efficient, flexible and accurate     

一种新型故障定位方法的研究

故障定位是电力系统事故处理的前提。传统的专家系统方法需要建立复杂的知识库,且实时性得不到保证。文中论述了利用因果网技术进行故障定位的方法,因果网描述了故障元件、继电器、开关之间内在的动作关系;提出了利用面向对象技术形成因果网的方法,所形成的因果网能适应各种不同的网络,通用性强,且能考虑故障扩大的情形。     

An expert system for the back-up protection of a transmissionnetwork

A back-up protection scheme for a transmission network is described in the paper. The back-up protection uses an action factor-based expert decision system (referred to as the BPES) to provide optimal fault clearance for faults located anywhere on the protected network. To achieve an optimal response, the BPES needs to know the topology of the network and the operating response of existing protection relays. Based on this information, the expert decision system will try to identify the feeder that contains the fault and which circuit breakers need to be tripped to clear the fault     

A comprehensive method for break points finding based on expert system for protection coordination in power systems

Interconnected power systems are multi-loop structured. In such networks, the determination of settings for all overcurrent relays can be carried out in different forms and may be quite complicated. The main problem for coordination is the determination of starting points, i.e. the location of starting relays in the procedure for settings, which is referred to as break points. In this paper, a powerful approach based on expert system is applied. The rules of the expert system include network configuration, protection systems, fault levels, etc. The method is applied to two networks with different configurations, pilot protection and other protection systems. From the obtained results, it is reviled that the new method is efficient, accurate, comprehensive and more optimal than the previously used graph theory.     

基于贝叶斯网络的电网故障诊断

针对电网故障诊断中存在的信息具有不确定性的问题,依据元件故障、保护动作和断路器跳闸之间的内在逻辑关系,由Noisy-Or和Noisy-And节点组成贝叶斯网络和采用类似训练多层前馈神经网络的误差反传算法进行诊断模型的参数学习,分别建立了线路、变压器和母线的通用故障诊断模型;依据元件-保护-断路器间的关联关系,给出了元件诊断贝叶斯网络的自动生成方法,最后对各个元件的诊断网络进行推理,以获得元件的故障概率值。实例仿真表明了该诊断方法的可行性和有效性,无论简单故障或多重故障,并且存在保护和断路器拒动、误动的情况下,都能得到合理有效的诊断结果。     

Expert system for protection coordination of distribution system with distributed generators

Distributed or dispersed generation may cause various complexities to the operation of distribution system. Therefore, it is of interest to propose an expert system for protection coordination of distribution system under the presence of distributed generators. The expert system employs knowledge base and inference process to improve coordination settings of protective devices in order to accommodate the penetration of distributed generators. The expert system feeds input data by using graphical user interface and develops coordination settings based on power flow and short-circuit analyses. The expert system has been developed and successfully tested with a 22-kV distribution system with multiple distributed generations.     

Development and hardware implementation of a reliable protective relay data acquisition system

This paper proposes an intelligence based protective relay data acquisition system to correct current transformers and capacitive voltage transformers secondary waveform distortions. The protective relay data acquisition system receives voltage and current signals from current transformers and capacitive voltage transformers and prepares the inputs to the main board after some pre-processing. Current transformers and capacitive voltage transformers provide instrument level current and voltage signals to meters and protective relays in high voltage and extra high voltage systems. The accuracy and performance of protective relays in high voltage and extra high voltage systems are directly related to steady state and transient performance of current transformers and capacitive voltage transformers. Current transformers saturation and capacitive voltage transformers transient could lead to protective relay mal-operation or even prevent tripping. The key of the proposed scheme is to use artificial neural network to achieve the inverse transfer functions of current transformers and capacitive voltage transformers. Simulation studies are preformed and the impacts of changing different parameters are studied. Performance study results show that the proposed scheme is accurate and reliable. The proposed algorithm has also been implemented and tested on a digital signal processor board. Details of the implementation and experimental studies are provided in the paper.