共查询到20条相似文献，搜索用时 31 毫秒
1.
XIAO Yong~ 《保鲜与加工》2004,(11):30-33
The scheme of rapid protection will be possibly implemented by using the channel of communication, as the communication network of distribution power system being increasingly perfect and particular foundation of optical cable. The feeder protection based on communication can quickly and selectively isolate fault section and restructure the distribution network. This method is the direction of distribution automation. The action principles of feeder protection using blocking and allowing signals of directional over-current are analyzed. The directional over-current protection utilizing blocking signals is suitablefor distribution automation. The scheme can locate the fault section and instantly separate it. When feeder terminal unit (FTU) fails to act or communicate is interrupted, the feeder protection in the substation can backup. 相似文献
2.
Considering traditional current protection cannot satisfy the micro-grid, a system protection solution for the micro-grid is proposed. In this solution, the failure message with direction information can be exchanged among the adjacent protection units, so the fault coverage can be determined and the fault can be quickly cleared. By analyzing the movement of the protection in three kinds of fault conditions in the micro-grid that contains three branches and two micro-power based on inverter, the method has been proved that the fault can be quickly cleared and the protection has the same protection strategies for both islanded and grid-connected operation. 相似文献
3.
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. 相似文献
4.
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. 相似文献
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6.
Based on the study on the properties of Magnetic Inrush Current and Fault Current of power transformers, Saber is applied to realize the simulation of such conditions as no-load closing and all the fault conditions including turn-to-turn fault and turn-to-earth fault. Grounded on the wavelet analysis theory, a new method is proposed which can differentiate effectively the internal and external faults and detect the turn-to-turn fault. The simulation result shows its effectiveness. 相似文献
7.
A new principle and scheme of a Feeder Automation based system protection using the channel of communication is proposed. The conjoint protection devices exchanging fault signal with direction information and the fault can be cleared instantly. These information can hel Pto isolate the fault zone and restructure the network rapidly. The recover is used for instantaneous faults. The optical MODEM disjoins the SCADA communication and Boolean signals functions using coding technology. So the fault flags can be exchanged rapidly peer-to-peer and special optical cables are not needed. Frames between optical MODEM are sent automatically. This scheme presented is successful through physical simulation experiment and has operated for about two years in a real distribution network. 相似文献
8.
In order to improve the asymmetric fault ride-through capability of PMSG wind turbine, a novel control method is proposed. This method can reduce the negative sequence current component in the grid side converter and eliminate the 2 nd order voltage fluctuation in the DC link capacitor voltage of the AC-DC-AC converter. The proposed control method employs the grid voltage feed forward to reduce the grid side negative sequence current component, while a novel power control concept, output power of generator tracking the grid side power, is applied to control the electro-magnetic power of the PMSG to eliminate the 2 nd order voltage ripple in the DC link. Simulation results for a 1 MW case study show that the control method can eliminate the grid side negative sequence current component and the 2 nd order voltage ripple in the DC link at the same time. 相似文献
9.
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. 相似文献
10.
The reliability and reality of load historical data is the foundation of load forecasting.But,the impact load in running power system,and the disturb data in collecting load data through the SCADA may cause much fault data in load historical data. Focusing on solving this problem, a method through adjusting amplitade of its wavele modulus maxima and processing the wavelet decomposed detail signal by soft threshold based on wavelet analysis and singularity theory, then fault date can be eliminated,so that,the real historical imformation and regulation data can be gained by load forecasting. 相似文献
11.
Yao Zaoxin Ye Yilin 《保鲜与加工》1990,(4):14-22
In accordance with the characteristic of digital relay and fault locatoin four methods of phase selection on fault component are presented in this paper.These methods are simple in principle, reliable in action, and immune from load flow,system oscillation.Hardly affected by fault location, source impedance and fault resistance, they can select fault phase reliably for any power system and fault type.As phase selection schemes, they can be used for perfect digital relay. 相似文献
12.
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. 相似文献
13.
A new method to calculate electric values of unsymmetrical open conductorfaults in power systems with variable structures and parameters is proposed. All the fault componentsof nodal voltage or branch current and the equivalent parameters of open port for each sequence net-work can be obtained rapidly. The method presented here is much more understandable in contrast tothose available, and meanwhile the amount of calculations is greatly reduced. Its effectiveness hasbeen verified by numerical examples. 相似文献
14.
Considering the limitation of the field test for relay protection in power system, the paper studies and discusses the remote test method of relay protection in power system. It provides the technology requirements, the technology problems and restricted factors to build the protection test and analysis center. It proposes the method of building the protection test and analysis center. Considering the practice for the transmission of test data, the paper introduces the technology requirements of utilizing dispatching automation system data network to transmit the protection test data. Considering the requirements of microcomputer protection devices for remote test method, the paper presents that there are remote test function and synchronization test function in the field microcomputer protection devices. 相似文献
15.
Novel method for fault line selection in arc suppression coils system using transient energy 总被引：1，自引：0，他引：1
In order to overcome low sensitivity of the protection based on transient components when the faulty voltage passes zero, regarding arc suppression coill branch as a healthy feeder line, using the relation of its transient energy and all feeders of transient energy amounting to zero, this paper presents an improved fault line selection method in arc suppression coils system using transient energy. This method has no requirements of detection fault close angle and pre setting, has a good anti interference ability and adaptability to various faults occurred in the systems with arc suppression coils. Large amount of digital simulation results show that the proposed method is effective and reliable. 相似文献
16.
Mi Linshu Liu Fangning Chen Gang 《保鲜与加工》1992,(1):70-76
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. 相似文献
17.
Mi Linshu Liu Fangning 《保鲜与加工》1988,(3)
A straightforward and unified approach for solving the large-scale, faulted power systems is presented in this paper. In contrast .with conventional algorithms, the various changes of topology and impedance of the systems and its boundary conditions of fault can be handled flexibility and effectively in one-step procedure by proposed method, and it is convenient to choose the computational procedure more resonable according to the situation of power systems. One of the noteworthy features of the proposed method is the natural manner to handle mutual effects, and it is easy to design programs. The calculating technique for easy-to-program is given in this paper. It shows that effectiveness of calculating large-scale faulte power systems with topology and impedance changes by the modified current sources. 相似文献
18.
As an optimal method, Genetic Algorithm has obvious advantages, which is based on the nature selection and genetic transmission mechanisms such as high collateral,stochastic,self-reliance. but when in practical application, it usually has problems of premature convergence and result swing near optimum value.To solve the problem of premature convergence, the method called Monte-Carlo is adopted to prevent the algorithm from local optimal, and to the problem of result swing, the method changing the hunting zone dynamically is proposed to improve the accuracy of the optimal result. Further more, it devises programs to optimize the test functions of two famous optimal methods. The test results indicate that the improved Genetic Algorithm is valid, which can not only avoid local optimal but also improve the accuracy of the optimal result. 相似文献
19.
Based on the thorough analysis of typical failure modes and influences of on-load tap-changers in power transformer, the fault-tree of tap-changers is set up using fault-tree analysis techniques and the assessment method for the reliability of tap-changers, combined with the index of the importance and the weight integration method based on the multi-objective decision-making theory and subjective and objective integrated weights, is put forward. The assessment examples show that the method can deduct and ratiocinate the failure modes of tap-changers clearly, find out the weaknesses in time during the operation, reflect the influence degree of each fault modes, obtain the reliability level of tap-changers in the operation and get better assessment results. 相似文献
20.
Yao Jiafei 《保鲜与加工》1994,(2)
This paper discusses the model for lifting capacity of the crane and optimal con-trol of eliminating swing in lifting process. One half loop control method is presented, which is onlyto examine and measure the trolley speed for eleiminating swing.The fact shows this methOd is sim-ple and practicle for enginceering. 相似文献