Small Current Grounding System Based On Fuzzy Fusion Of Multi-level Data Research On Single-phase Line Selection Method

In China’s 6-66 k V distribution network,small current grounding system,also known as neutral ungrounded system,is widely used.When single-phase grounding fault occurs,it can operate for 1-2 hours with fault according to relevant regulations,and the power supply reliability is high.However,the formation of overvoltage will threaten the weak point of the system insulation,in addition,it is easy to cause insulation flashover and further expand the accident,so it is necessary to quickly and accurately select and cut out the fault line.At present,although there are various line selection methods,the effect is not satisfactory,the main reason is that the single line selection method has limitations,and the adaptability of working conditions is poor,resulting in a certain gap in accuracy.Therefore,the integration of a variety of line selection methods for comprehensive line selection,is the current research trend.In this paper,the research background and significance of single wire grounding fault in small current grounding system are described,and the current status of line selection methods at home and abroad is briefly analyzed.The steady-state and transient characteristics of each line before and after single-phase grounding fault are analyzed.According to different grounding modes,the steady-state and transient characteristics of fault line and non-fault line are compared,which lays a theoretical foundation for the research of line selection method.Secondly,three simulation models of neutral resistance of 10 k V3 return line inductive grounding,neutral ungrounded,and distributed capacitance unbalanced neutral point grounding through arc-suppression coil are built.At the same time,considering the asymmetry of distributed capacitance and the difference of grounding resistance,some widely used current line selection methods are studied.The line selection effect of these methods and their applications are analyzed one by one.The results show that single line selection method is not effective in line selection.Finally,by comparing and analyzing the principle,advantages and disadvantages of the existing single-phase grounding fault line selection methods of small current grounding system,a multi-information fusion integrated line selection method is studied.In this method,a multi-stage fuzzy fusion algorithm is designed based on a variety of fuzzy operators,and the intelligent selection of weight coefficients of a variety of single line selection results is realized,and the subjectivity of weight coefficient selection is avoided.The superiority of this method in accuracy and adaptive ability is verified by simulation experiments.