Analysis on the method of selecting nodes on the erosion diagnosisof grounding grid

The number of underdetermined equation, which is limited by the grounding down lines, reduces the grounding grid corrosion diagnostic precision. Based on the grounding grid fault diagnosis method and sensitivity analysis, the value of slip resistance change on the impact of the port resistance in several cases, such as small span, large span and edge, center and symmetrical cross line of the grounding grid, is analyzed. A new method which is used to select the node pairs to calculate the corrosion situation of grounding grid is presented. Based on this method, the simulation analysis and field test has been done. The experimental results show that this method could improve the accuracy and efficiency of grounding grid fault diagnosis.     

Analysis of Theory and Method about the Corrosion as well as the Broken Point of the Grounding Grid

The paper studies the theory about the corrosion as well as the broken point of the grounding grid in power plants and substations. By using sensitivity analysis, failure diagnosis equation is put up through rigorous theoretical analysis. Meanwhile the problem of morbid equation is solved by introducing lowest energy theory and technique of optimiation to diagnosis equation solution of grounding grid combined with definite constraint condition and linear or non-linear objective function, the fault diagnosis equation is discussed. The results of emulation calculation and analogous experiments verify the correctness,feasibility and practicality of the theory and method.     

Erosion Optimized Diagnosis of Brand Grounding Grid

To find the corrosion of the grid ,large area cutting has been adopting in practice for a very long time. But this method is blind, difficult and influences the system operating. The erosion diagnosis method in the past is effective for the smaller grid. To the brand ones, it can not take effect. The method of separating the grounding grid into several parts and diagnosing step by step is discussed by lots of simulation about middle or brand grounding grid erosion diagnosis. This method makes the brand grounding grid erosion diagnosis quick and truly without power cut and digging large area, satisfies the demand in practice. Putting this optimized diagnosis method into practice , the result is good.     

Limiting the Arc Over-voltage of 10 kV Grids in Application of Nonlinear Resistance

The aufhors calculate and analyze the arcing grounding overvoltage of 10 kV power network in case of neutral ungrounded and grounding through nonlinear resistance using EMTP, with a actual 10 kV power network of a substation in Guizhou province as an example. The emulational calculation results show that the grounding method which grounds through nonlinear resisitance has the advantages of the other two methods, can better limit the arcing grounding overvoltage and can not stop the power supply .even one phase is grounded by fault, so it can ensure the security of the power networkg supply . the network neutral grounding through nonlinear resistance needs more deep study and analysis as a new network neutral grounding mehtod.     

Computation method of magnetic field inverse problem on grounding grids fault diagnosis

Grounding grids are the guarantee of substation running safety. The fault of grounding grids is a threat to people and equipment in substations. A method to diagnose the fault of grounding grids based on magnetic field inverse problem. The inverse problem of magnetic field is established by injecting and extracting a low frequency current. The morbid of inverse problem is solved through regularization and Newton iteration method to obtain the distribution of the mesh currents. The approximate distribution of the magnetic field is calculated to diagnose the fault of the grounding grid. A 4×4 substation grounding grids is taken as an example. By comparison of the forward problem result, the error is under 3%, so the prposed method of inverse problem is verified. The selection of measurement point is discussed, and 40% of the number of meshes is accounted to approximate the real distribution of the magnetic field on the grounding grids.     

Simplified Method for Calculation of Current Distribution on Grounding Electrodes

A new method is presented to calculate the non-uniform of current distribution on grounding electrode. Based on the equivalence of low frequency current field and static electric field, the electrode is simplified to he a line charge model with limited length. The charge distribution on the model is calculated by solving equilibrant equations, and the current distribution along the axis of electrode was got. The current density at the end of electrode can he several times of that in the middle, the non-uniformity get worse with the increasing of electrode length and numbers. This is what lead to several problems on grounding systems such as inefficiency, the partial overheat and the severe corrosion of electrode.     

Research and Application of Information Fusion Technology on Machinery Fault Diagnosis

Aiming at insufficiency exists in the process of machinery fault diagnosis at present, the paper takes consider of the application of information fusion technology in fault diagnosis to make fault diagnosis effectively. The applications of information fusion methods based on neural network, the Bayesian theory and the D-S theory are discussed in detail. Example is also given to explain the validity of information fusion technology in diagnosis analysis.     

Fault Section Diagnosis Algorithm of Distribution Networks Based On Topology Identification

An algorithm of fault section diagnosis based on topology identification for distribution networks is presented. By decomposing the topologic matrix which describing the distribution network into two parts,one part only contain the complex coupling factor ,and the other ignore the complex coupling factor. Using this method, the fault zones in distribution network can be identified and isolated efficiently, and the vertexes of the zones can also be identified automatically. This approach adapts to the changefully network structures.     

基于传输线网络的特高压变电站智能组件端口电磁骚扰的建模仿真

随着智能化GIS设备的发展,GIS设备上集成了大量电子设备。GIS设备开关操作产生的特快速瞬态电磁过程主要经由“传感器—二次电缆—智能组件”这段电路对电子设备产生电磁影响。笔者首先基于传输线网络理论建立了开关操作产生的地电位升对“传感器—二次电缆—智能组件”回路的耦合计算模型,然后通过验证实验证明了计算模型的有效性和准确性,最后对不同屏蔽层接地方式下的各传感器端口和智能组件各端口及端口间的骚扰电压进行了仿真研究。计算结果显示,各骚扰电压受接地方式的影响较大;通过选择合适的接地方式,可以有效地抑制开关操作电磁骚扰。     

HIGH SPEED CALCULATIONS OF SHORT CIRCUIT FOR POWER SYSTEMS WITH VARIABLE STRUCTURES AND PARAMETERS

This paper presents a new method for digital simulation of equivalent circuit parameters and port currents of the short circuit fault port for each sequence networks in power systems with variable configuration and parameters. If the electric values for single-line-to-ground short ciruit are calculated in detail,the other faults at the same location can be rapidly obtained by using the proportional coefficients of the same sequence port current. In this method,the modifications of Z-bus or Y-bus matrices for each sequence network, and the repeated of calculations of the short circuit calculation have been completly avoided.     

Artificial Neural Network Fault Diagnosis System Based on Rough Set Theory

On the basis of fault diagnosis neural network model, in this paper, knowledge representation system of rough set theory is taken as a major tool to delaminate the complex neural network and in which unnecessary properties are eliminated. This method overcomes some shortcomings, such as network scale is too large and the rate of classification is slow. The good effect that reduces the matching quantity of pattern search in classification course is gotten. The structure and algorithm of layered-mining neural network model based on rough set theory are also given. The example shows that this system has higher reference value in practical application.     

Comprehensive Intelligent Wire-selection of Neural-based Small Current Grounding System

This paper centers on the study of intelligentized fault lineselection when the small current grounding electric system is grounded in single-phase. Based on the known theories and methods of groundingline-selection, we propose a comprehensive neural-based intelligentized processing plan, which offers a new approach to improving accuracy rate of fault line selection andevaluating various arithmeticfor grounding protection in practice.     

Study on the Method of Intelligence Fault Diagnosis System for Drill

It is very difficult to simulate the motion process of drill by accurate mathematics model for the complexity and invisibility of stratum. The fault of drill is usually identified and disposed by personal experience so far. This means it can not estimate the trend of the equipment running good or not and the reason conduced the fault or location and degree of fault by data measured. Farther, it can not give the expert suggestions. Based on the studying of drill fault, artificial intelligence and expert system have been used in the petroleum drilling engineering, the theory and method of fault diagnosis intelligence system for drill have been studied. It also constitutes the expert knowledge database of graphic Fuzzy Neural Network for the familiar fault of drill. The intelligence reasoning machine which consists of expert rule, Fuzzy logic and artificial Neural Network have been bring forward. And the fault diagnosis system it makes for drill can be applied in complex system which includes multi-variable, multi-parameter and multi-process.     

Parsimonious Covering Probability Model for Turbogenerator Vibration Faulty Diagnosis

The turbogenerator vibration faults have the character of variety. Many faults often occur synchronously. This paper introduces a diagnosing model based on parsimonious covering theory and probability. A model for turtogenerator's fault diagnosis is proposed. The availability of this method is proved by two fault diagnosis examples of turbogenerator. The results show that the model proposed can be used for multi_fault diagnosis together. It may make up shortage for some of expert systems and neural networks in some aspect. From the practice,this model has higher reliability and practicability.     

励磁功率单元主回路快速故障诊断策略

分析总结了发电机组励磁系统功率单元的故障类型和常见故障,通过Matlab仿真功率单元主回路故障类型,重点研究基于故障频谱分析的定量故障特征提取和故障分类,提出了一种快速针对功率单元主回路的故障诊断真值表法,最后通过实验平台验证故障类别,结果表明：该方法能够正确有效地诊断出功率单元主回路具体的故障晶闸管,为励磁系统功率单元故障诊断提供依据。     

New Operation Method of 35 kV Power System in Mountainous Area

The unbalanced nature of 35 kV distribution system due to capacity values is difficult in neutral operation, which can not meet the demand of voltage balance in static state and arc distinct in fault. This paper proposes a new neutral operation as neutral insulation in static state and resonance grounding in fault , along with EMTP simulation acts. Simulation indicates that new neutral operation method can improve lightning withstand level and decrease trip-out rate of grids.     

Analysis of Information Flow Based on Entropy of Fault Diagnosis

Under the pointview of epistemology and generalized information theory, fault diagnosis can be regarded as the state identification process by dint of various cognitive tools. Therefore, information Entropy can be employed to explain the transfer of information during identifying the faults. The mathematical deduction of information Entropy is given and the idea of Multi-Symtom Domains Comprehensive Feature Knowledge to solve fault diagnosis problems caused by insufficient knowledge and lower cognitiving ability for complex knowledge system is presented.     

Malfunction Diagnosis of Three-phase Full-bridge Controlled Rectifier Based on BP Neural Network

The diagnosis of the power electronic circuit is very intricate. One of the main reasons is that the structure of the circuit will change if the power device is not working .The thyristor is the easiest to be mangled. So diagnosing the malfunction is the most important about the diagnosis of the power electronic circuit. The paper puts forward a malfunction diagnosis of the thyristors of three-phase full-bridge controlled rectifier with BP neural network. After analyzing the output waveforms of malfunctioning circuit and training a BP neural network with the sampling data of malfunctioning waveforms, a well training BP neural network is constructed and used to diagnose the malfunction. The simulation and experiment demonstrate that this method is valid.     

State and Prospects of Diesel Engine Fault Diagnosis Technique

As a kind of complex power machinery, diesel engine is being paid more and more attention to its condition monitoring and fault diagnosis technology. In the fault diagnosis field of diesel engine, the technique of signal process, character abstraction and identification method have formed a system, but there is a certain distance away from practical. This paper analyzes the common faults and influencing factor of diesel engine. The principle, characteristic and disadvantage of modern fault diagnosis technology, such as various time-frequency methods based on vibration signal, speed fluctuation method, iron content and spectrometry, grey system theoretical diagnosis method, artificial neural network and expert system fault diagnosis method, were reviewed. The difficulties and the development direction of diesel engine fault diagnosis were put forward in the end.