Title: Single phase small current grounding system of fault line selection
ABSTRACT Small current grounding system to improve power supply reliability in the superiority, which in our distribution network has been widely used. The system is single phase ground fault at the highest risk, when a small current grounding system, single-phase ground fault occurs, the formation of a long ground run two or more points easily ground short circuit, grounding can also cause system-wide arc over voltage, damage the safe operation of the system, how to troubleshoot quickly and accurately route, the operation of the system is significant. However, due to single-phase ground fault resulting fault current is very small, and many other reasons, the single phase to ground fault line problem has never been solved. In this paper, this research work aims to find ways of existing shortcomings in alignment, and further explore the fault line selection method. As a basis for research work, the first systematic analysis of this small current grounding system fault occurs the characteristics of single phase, from both transient and steady state characteristics of the fault and fault lines in the normal amount of the difference in line for this article provide a theoretical basis for later work. In the theoretical analysis, based on the alignment of the existing methods of a simple, analyzes the limitations of a variety of line selection, summarized the main reason the current alignment difficulties. Finally, it was based on a single line selection methods have their respective limitations, address the method to select reasonably comprehensive, method to select between a variety of play complement each other, forming an integrated multi-line selection criteria. This paper has proposed a comprehensive method to select improved to failure as the benchmark measure, the integration of groups than the amplitude of zero sequence current law, injecting signal, based on zero sequence current harmonic distortion characteristics of line selection method, the transient zero sequence current summation of each product, decaying line selection method and the wavelet packet analysis of six Line selection method to select, construct a multi-criteria based on fuzzy comprehensive method to select. A variety of single fault line selection method set membership function and the criterion measure of the weight coefficients of the membership function. According to the system structure and the amount of a variety of fault feature, the fuzzy decision-making to get the final alignment result. And the improved method to select for the integrated digital simulation, and achieved the expected results, proof of its validity and reliability. Finally, the current traditional method to select only the information by the fault under test fault line selection, without samples used to have trouble on the Fault Line contains a lot of favorable information, this paper has been based on fault samples of fault information Based on the analysis presented, Grey relational analysis tested the new fault line selection, established based on the injection signal and the wavelet packet decomposition of the gray relational analysis method of fault line. And through a large number of digital simulation experiments to verify the established alignment system is feasible. Grey relational analysis method to select the train of thought from the choice of lines is different from the traditional method to select, has opened up a new fault line the road, with the improved multi-criteria based on fuzzy comprehensive method to select the combination can play an effective role in verification, the accuracy of alignment will be greatly enhanced, the small current grounding power for the current single-phase to ground fault line has a certain practical significance difficult. Key words： small current grounding system; fault line; failure measure; information fusion: fuzzy theory; Grey relational analysis
