Font Size: a A A

Research On Fault Line Selection And Fault Location Technology In Neutral Un-effectual Grounding System

Posted on:2014-02-25Degree:MasterType:Thesis
Country:ChinaCandidate:W S WuFull Text:PDF
GTID:2232330398957394Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
The operation mode of neutral un-effectual grounding system (NUGS) can significantly improve the reliability of power supply, thus it is widely used in power distribution network in China. Most of faults in distribution network are single phase-to-earth fault, when the fault lasts for a long time in NUGS, it will cause a serious of consequences, such as overvoltage, multi-point grounding, equipment destroyed and the safe operation of power system damaged. So when single-phase-to-earth fault occurs in NUGS, it is necessary to select the fault line quickly. Due to the weak fault current and many other factors, the fault line selection and fault location problem has not solved successfully for many years.In this dissertation, under the background of the research work, it hopes to explore a new method to select fault line and fault location through the excavation of the existing methods. First of all, the dissertation reviews the development status of fault line selection and fault location methods in NUGS. Then, different distribution network neutral grounding type of single-phase-to-earth fault is discussed, also the details of the fault steady state and transient zero sequence current component are analyzed. The change rule of notable fault characteristics is summarized, which provides theoretical basis for follow-up study.There are many existing fault line selection methods. This dissertation summarizes the causes of the line selection device misjudgment. Then, because each method has its deficiencies, a solution which should make full use of complementarities between each method has been proposed. A reasonable criterion of fusion fault line selection method is formed. When variety of criterion is selecting the fault line, characteristics quantities of fault is not clear. The fault line selection program based on fuzzy theory is proposed in this dissertation, and two key problems are solved:one is the choice of basic criterion. After comprehensive comparison, four kinds of fault line selection method are choosing to form a criterion of the fusion fault line selection program, which contains the zero sequence fundamental component method, the five time harmonic component method, the energy function method and wavelet analysis; another one is building fault membership function. According to the differences between characteristics quantities of fault, the conception of fault measure and weight coefficient to the selected criterion is introduced. The fault measurement function and weight coefficient function also have been set up. Finally, the paper uses MATLAB power system simulation toolbox to build a typical lOkV distribution system whose simulation results verify the feasibility of the fault line selection method.The dissertation further analysis of transient fault signal characteristics and proposed a new fault location method based on transient signal. First analyzing the attenuation characteristics of the transient signal before using FFT tool to determine the effectiveness of the charge transient signal and identify by its frequency. Then extracting the transient signal characteristic of fault phase voltages and phase currents by complex wavelet transform, further calculating fault distance. The simulation results demonstrate the fault location method is reasonable.
Keywords/Search Tags:distribution network, fault line selection, fault location, Fuzzy Theory, transient signal
PDF Full Text Request
Related items