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The Study And Application Of Method Of Fault Line Selection For Single Phase-to-ground Fault In Distribution Network Based On Wavelet Theory

Posted on:2005-09-02Degree:MasterType:Thesis
Country:ChinaCandidate:N WangFull Text:PDF
GTID:2132360125458707Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
Neutral non-grounded and Petersen-coil grounded systems are also called neutral un-effectual grounded system (NUGS), and they are widely used in power distribution network in China. The single phase-to-ground fault happens most frequently in distribution network. Due to the small fault current and unobvious fault features after single phase-to-ground fault, the problem of fault line selection has been studied for years, however it is still not solved perfectly, which has seriously blocked the development of reliability of power supply and automation level of distribution network.Firstly, stable and transient features of single phase-to-ground fault in NUGS are deeply analyzed in this thesis and lots of dynamic simulation experiments have been made. Both theory analysis and experiment results show that there are many high frequency component features in transient fault currents, and extracting the fault features can form a novel fault line selection criterion. Wavelet analysis is localized both in time domain and frequency domain, and can cut any signal into different frequency components, which makes it a suited tool for analyzing unsteady signal and transient signal. Theories and concepts about wavelet analysis are described in detail, which provides theoretical basis for the extraction of fault features. Then, combined with the advantages and disadvantages of the existing fault line selection methods, a new approach based on wavelet transform is presented. The fault line is detected in terms of the features of magnitude and polarity of wavelet coefficient of transient zero-sequence current in certain scale, thus the proposed method overcomes the limitation of steady and other transient approaches. Simultaneously, some problems faced in fault line selection using wavelet transform, such as how to select wavelet function and determine the decompose scales etc, are discussed in this thesis. Successionally, the feasibility of realizing fault line selection by means of FTU in distribution automation system is demonstrated, main thought is described, hardware configuration of FTU is detailed, and software about the method based on wavelet analysis is studied and designed. Finally, lots of dynamic simulation experiments testify that the proposed method can quickly and exactly select the fault line for single phase-to-ground fault in NUGS, and it is suitable for various distribution networks with different neutral grounding modes.Advanced wavelet theory is applied to solve the technique problem of fault lineselection for single phase-to-ground fault in NUGS in this thesis, which makes important theoretical sense and significant practical value.
Keywords/Search Tags:Distribution network, Neutral un-effectual grounded system, Fault line selection, Wavelet theory, FTU (Feeder Terminal Unit)
PDF Full Text Request
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