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     

电力变压器信息管理及故障诊断专家系统的研制

介绍了变压器故障诊断专家系统的情况,描述了所开发系统的TFDES结构、推理机制、实现方法及诊断管理的主要功能。现场测试表明:TFDES结构合理,推理正确,能有效诊断运行中变压器的内部故障。     

基于MMC的电力电子变压器保护系统研究*

介绍了基于MMC的电力电子变压器主电路拓扑及运行原理;对其可能出现的故障类型配置了相应的故障量测点以及保护方法;对MMC型电力电子变压器中存在的特殊故障及保护问题进行了详细分析,包括交流输入侧接地电阻的选择对交流侧接地故障和直流侧单极接地故障的影响,直流双极短路故障发生后采用具有直流故障电流抑制能力的箝位双子模块替换半桥子模块之后产生的过电压问题,以及电力电子变压器隔离级串联电容迅速放电产生冲击过电流问题;针对以上问题提出了相应的保护应对策略,并通过PSCAD仿真证明了所提策略的正确性和有效性。     

Potential applications of expert systems to power system protection

Working Group D10 Applications of Expert Systems to Power System Protection of the Line Protection Subcommittee, Power System Relaying Committee, was organized in 1989 with the following assignment as finally adopted: “Survey expert system technology to identify suitable and significant applications to power system protection. Write a technical paper that introduces protection engineers to expert systems and describes several potential applications”. This paper represents the work performed by the Working Group in fulfilling its assignment. The paper is divided into sections that describe a number of potential applications thought to be significant by the members of the Working Group     

10kV电力变压器的防雷保护

10kV电网的供电面积大、线路长,没有避雷线,容易受到雷害.10kV电力变压器数量最多,雷害后直接影响供电.分析表明,雷击作用到变压器上产生的雷电过电压包括3个分量:避雷器残压、接地引下线的电压降和接地装置上的电压降.相关计算显示,10kV避雷器放电动作时.接地装置上产生的电压降最大.在防雷保护的改造工程中,能够实施的工程措施是:降低接地电阻,以减小接地装置上的电压降:在变压器附近的电杆上安装辅助火花间隙,以限制侵入雷电波的幅值.另外,将避雷器接地引下线与变压器外壳连接,减少避雷器引下线长度,也是重要的技术措施.     

地方电网继电保护整定计算专家系统的研究

应用面向对象的方法 ,结合地方电网的实际特点 ,开发了一套分散式的继电保护整定计算专家系统。该系统把数据和知识库分散封装于不同的对象 ,通过消息传递进行相互配合 ,能较好地完成数值计算和逻辑推理 ,实验结果令人满意 ,目前整个系统正在完善中     

An expert system for voltage and reactive power control of a powersystem

A methodology called the sensitivity tree, which can be easily used to form an expert system for real-time control, is proposed. Based on this methodology, an expert system for the control of voltage and reactive power of a power system is developed. The main objective of this expert system is to help the operator detect buses experiencing abnormal conditions, select the most effective control measures, and calculate the control actions required to overcome the voltage violation. The control measures used to alleviate the voltage problem are capacitor compensation, transformer tap changes, and generator terminal voltage changes. By keeping the bus voltage in the entire system within limits, system security is increased. The expert system is written in the PROLOG language. Simulation studies with this expert system applied to a 30-bus power system show satisfactory results     

地方电网继电保护整定计算专家系统的研究

应用面向对象的方法,结合地方电网的实际特点,开发了一套分散式的继电保护整定计算专家系统.该系统把数据和知识库分散封装于不同的对象,通过消息传递进行相互配合,能较好地完成数值计算和逻辑推理,实验结果令人满意,目前整个系统正在完善中.     

直流单极-大地方式谐波特性及其对交流保护影响的分析

直流输电系统单极-大地运行方式对交流电网继电保护产生影响的根源在于直流偏磁导致电力变压器谐波以及电流互感器传变特性的变化,基于PSCAD/EMTDC电磁暂态仿真程序对直流偏磁下的变压器谐波特性以及保护用电流互感器传变特性进行了全面的仿真分析,得出相应的变化规律与特点,并以此为基础分析和评估了直流输电系统单极-大地运行方式对交流电网保护的影响.     

直流单极-大地方式谐波特性及其对交流保护影响的分析

直流输电系统单极-大地运行方式对交流电网继电保护产生影响的根源在于直流偏磁导致电力变压器谐波以及电流互感器传变特性的变化,基于PSCAD/EMTDC电磁暂态仿真程序对直流偏磁下的变压器谐波特性以及保护用电流互感器传变特性进行了全面的仿真分析,得出相应的变化规律与特点,并以此为基础分析和评估了直流输电系统单极-大地运行方式对交流电网保护的影响。     

An expert system methodology for determining the characteristics of power system component failures

The objective of the paper is to describe an expert system methodology which has been developed for determining the most likely nature, cause and expected duration of failures occurring in power system components. The inference engine task is based on Bayes' theorem and the knowledge acquired during the study of the historical outage records of the power system. This study allows the expected values of outage rates and durations to be evaluated for all component categories and groups. This expert system methodology can be a very useful tool with which to determine the most likely expected duration of a failure and to select the most appropriate operational actions to be performed. An example of application of this methodology to failures occurring in power transformers is also included.     

大接地电流系统中变压器间隙保护的应用

通过对大接地电流系统脱离主网后的接地故障情况及断线和非同期合闸造成的非全相运行的分析,阐述了大接地电流系统脱离主网和非全相运行时,造成变压器中性点电压位移而带来的危害,提出了主变间隙保护在大接地电流系统中的应用及建议。     

大接地电流系统中变压器间隙保护的应用

通过对大接地电流系统脱离主网后的接地故障情况及断线和非同期合闸造成的非全相运行的分析,阐述了大接地电流系统脱离主网和非全相运行时,造成变压器中性点电压位移而带来的危害,提出了主变间隙保护在大接地电流系统中的应用及建议.     

继电保护整定计算专家系统在四川电网的应用

介绍了110～500kV电网零序电流保护、相间距离保护、接地距离保护整定计算专家系统在四川电网的实际应用情况及其产生的经济效益和社会效益.实际应用表明,该专家系统具有较高的实用价值和推广应用价值.     

继电保护整定计算专家系统在四川电网的应用

介绍了 110～ 5 0 0kV电网零序电流保护、相间距离保护、接地距离保护整定计算专家系统在四川电网的实际应用情况及其产生的经济效益和社会效益。实际应用表明 ,该专家系统具有较高的实用价值和推广应用价值     

小电阻接地系统中接地变压器零序电流保护改进

配网中性点经小电阻地方式下发生单相接地故障时,传统的主变低压侧接地变压器的零序电流保护方案在保护动作时可能会不必要地跳开变压器低压侧2个分支断路器,导致事故停电范围扩大.现提出一种改进方案:利用故障发生时变压器低压侧两分支中流过的零序故障电流分布特征识别变压器低压侧故障分支,优先切除故障分支,避免停电范围扩大,当无法确...     

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.     

A denoising-classification neural network for power transformer protection

Artificial intelligence (AI) can potentially improve the reliability of transformer protection by fusing multiple features. However, owing to the data scarcity of inrush current and internal fault, the existing methods face the problem of poor generalizability. In this paper, a denoising-classification neural network (DCNN) is proposed, one which integrates a convolutional auto-encoder (CAE) and a convolutional neural network (CNN), and is used to develop a reliable transformer protection scheme by identifying the exciting voltage-differential current curve (VICur). In the DCNN, CAE shares its encoder part with the CNN, where the CNN combines the encoder and a classifier. Based on the interaction of the CAE reconstruction process and the CNN classification process, the CAE regards the saturated features of the VICur as noise and removes them accurately. Consequently, it guides CNN to focus on the unsaturated features of the VICur. The unsaturated part of the VICur approximates an ellipse, and this significantly differentiates between a healthy and faulty transformer. Therefore, the unsaturated features extracted by the CNN help to decrease the data ergodicity requirement of AI and improve the generalizability. Finally, a CNN which is trained well by the DCNN is used to develop a protection scheme. PSCAD simulations and dynamic model experiments verify its superior performance.     

New algorithms for power transformer inter-turn fault protection

In the paper new algorithms for detection of internal inter-turn faults in power transformers are described. Such faults are extremely difficult to detect since they induce negligible increase of the currents at the transformer terminals, although the currents flowing at the fault place are very high and dangerous for the transformer to be protected. The algorithms developed are based on the differential equation of the equivalent circuit of the transformer. In one version additional information from a CT installed inside of the triangle of delta side windings is used, which brings very promising results. Theoretical investigations are supported and illustrated with simulation studies performed both with MATLAB and EMTP-ATP programs.     

An expert system for distribution substation fault diagnosis and backup protection

Using Prolog, this paper presents an expert system for fault section diagnosis in a substation primary system, backup protection and fault finding in protective systems. The expert system is intended for use in distribution substations.