Analysis on the effect of substation structure on grounding grid corrosion diagnosis

The measured data of grounding grid corrosion diagnosis are often influenced by steel structural frames, and thus the diagnosis is inaccurate. Based on grounding grid corrosion diagnosis theory, the characteristics of structure frames number, length, layout location and resistance of the influence on the diagnosis result are analyzed by establishing the simulation model. The results show that regardless of the structural frames’ number, layout location and span length, the existence of structural frames reduces the diagnosis sensitivity of fault branch which is near structural frames, making the extent of diagnosed branch corrosion is lower than that without framing. However, the diagnosed corrosion of the branch which is away from the structural frames won’t be influenced. The bigger the resistance of the structural frames connected to grounding grid, the smaller the diagnosis result of interference. Choose the grounding grid branch which has no obvious increase multiples near structural frames as excavation object can improve the diagnostic accuracy.     

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.     

A Method for State Diagnosis of Grounding Grid

This paper discuses the method with which the corrosion of the grounding grid can be diagnosed .A grounding grid can handled as a circuit network. With the application of circuit network graph theory and the fault diagnosis theory of analog circuit and optimization, the fault diagnosis equations can be set up. This equations is figured out by Matlab, and the corrosion status of the grounding grid can be deduced from the result.     

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.     

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.     

The on line monitoring method of power transmission line fault basednon linear frequency response function

A novel method for power transmission line monitoring and fault diagnosis is proposed based on non linear frequency response analysis. The power line carrier signal has been used for on line monitoring of power transmission line. As the non linear frequency response function describes the system inherent characterization, different frequency response patterns corresponding to different operation states of transmission line can be established. Based on the analysis of transmission line characteristics of fault modes, various fault features can be extracted, thereby achieve online monitoring and fault diagnosis on transmission line. Simulation experiments show the effectiveness of the proposed method.     

A corrosion diagnosis method for optimized measurement of grounding grids

Simulated experiments of grounding grid corrosion were conducted based on two 220 kV substation models. In initial diagnosis, the measurement nodal points were planned to great span, small piecemeal, and large piecemeal jointing fixed points. A comparative study of the three measurement plans was carried out. The results show that the large piecemeal with fixed points had the best performance and could be used as a practical method for diagnosing grounding grid corrosion.     

Diagnosis approach based on failure mode importance of causality diagram

Causality diagram methodology is a probabilistic reasoning, which can be applied to fault analysis. However, it lacks analysis on the importance of failure mode. The importance of failure mode is introduced to develop causality diagram methodology, which is successfully applied in fault analysis of gas explosion in colliery. The study shows that causality diagram based on importance of failure mode is an effective qualitative and quantitative method to analyse faulty, evaluate system safety and provide feasible countermeasures to prevent accidents.     

Application on Extracting Feature in State Monitoring and Fault Diagnosis

With the development and application of information and internet and virtual instrument technology ,the virtual globular company based on internet arises .To study remote state monitoring, remote fault detection and diagnosis about large scale, complicated and integrative equipment become very important. In the whole fault diagnosis system , the detecting ,data acquisition is original ,processing; transform and extracting features with the signal detected is a key factor. The theories and methods used in mechanical fault diagnosis is stated. The application of signal process and its feature extracting methods is introduced which are time domain, frequency domain and time frequency domain analysis, in state monitoring and fault diagnosis with its signal analysis. The processing method of random time variant special signal is given also.     

Online MW-MSPCA data-driven fault diagnosis

To track the non-stationary dynamics of the process which contains time-varying and multi-scale data, an online moving window multi-scale principal component analysis（MW-MSPCA） data-driven-based fault diagnosis method is proposed. In this data-driven diagnosis technique, wavelet threshold denoising is used to solve the conflict between the statistical model deviation and data correlation decreasing. The statistical models are updated by using moving window principal component analysis in various scales. The contribution of individual process variable to the process behavior change is illustrated in a 3-dimensional contribution chart. A quantitative evaluation mechanism is also given to evaluate the diagonising accuracy. The numerical experimental results for 6135D diesel demonstrate that the proposed method can diagnose sensor fault better in terms of false rejection, false alarm and diagnosing accuracy for fault diagnosis upon comparing with conventional multi-scale principal component analysis（MSPCA） and adaptive multi-way principal component analysis（AMPCA） modeling.     

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.     

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.     

Grounding resistance measurement method of largegrounding grids with short current wire

The 0.618 method for grounding resistance measurement has long wire lead defect. By calculating and analyzing the ground potential of a large number of grounding grids which are different in shape, area and rod arrangement style using computer numerical method, it presents that the grounding grids can be equivalent to disc shape grounding electrodes. A new method of grounding resistance measurement is presented that taking the current electrode wire as long as the longer side length of grounding grids and voltage electrode wire as 0.509 times long as the current electrode wire. The measurement accuracy of this method is testified by experiment in field. The proposed method has much shorter wire than 0.618 method, it is suited to grounding resistance measurement of large grounding grids.     

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.     

A New Method of Diesel Engine Fuel System Fault Diagnosis

A method of diesel engine fuel system fault diagnosis based on wavelet transform and fuzzy C-means clustering is presented. Five characteristic parameters of reflecting fault state are distilled with wavelet transform of pressure wave of high-pressure oil pipe of diesel. The theory and generic approach of fuzzy C-means clustering algorithm (FCM) is given, and the validity of evaluating fuzzy clustering making use of partition coefficient, partition entropy and parting coefficient is pointed out. Identification of fault mode can be completed utilizing standard fault character modes established by FCM algorithm, and calculating and comparing the similarity degree between this standard mode and sample. The arithmetic is applied to all kinds of typical faults diagnose in the diesel engine fuel system. Measuring results indicate that the precision of fault diagnosis is increased with the analysis of wavelet and FCM.     

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.     

The Fault Calculation of the Transposed and Untransposed Transmission Lines

This paper presents a method which can accurately calculate the fault voltages and currents of the transposed and untransposed transmission lines.It can be applied to the simulation of protection relay analysis and fault location and so on.The principle of method is clear,the computational precision is high and usage is simple.     

Calculating the Hollowing-center Grounding Device Resistance Based on the Surface Charge Simulation Method

An equivalent model for hollowing-center grounding device is proposed, the hollowing-center grounding device resistance is calculated with the surface charge simulation method and the computer programme is programmed based on this model. The accuracy of the model and method is validated by experimentation.     

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.     

Effect of Polymer Coagulant on the Dewatering Characteristic of Sludge

Based on analysis of the characteristic of the sludge, in this paper, three kinds of sludge were selected to make coagulant experiment with three different coagulants. The specific resistance to filtration is tested. Finally,the optimum coagulant with its optimum dosage is obtained and the dewatering effect is improved.