Research On Single-phase Grounding Fault Line Selection In Small Current System

With the rapid development of my country’s social economy and the continuous construction of urban foundations,there are more and more complicated distribution network structures.In order to meet the reliability of power supply,it is necessary to eliminate all occurrences of the distribution network more quickly,timely and accurately.In my country’s medium-voltage distribution network the small-current grounding system is the mainstream,and in the small-current grounding power system the single-phase grounding has the highest frequency of failure.Line selection methods and line selection equipment have always been research hotspots,indicating that the technology is not fully mature.Therefore,it is necessary to study the single-phase ground fault test methods and line selection issues for small current grounding systems.Firstly,this article focuses on the situation of single-phase grounding faults in small-current grounded distribution networks in different types of grounding forms,and carefully analyzes the characteristics of the fault signals in the steady-state period and the transient period,and focuses on the changes in the zero-sequence voltage and current.Lay a theoretical foundation for the verification of distribution network modeling results and the study of route selection methods.Secondly,by studying the application scenarios of the low-current line selection device,a basic low-current grounding system model and various influencing factor models were established on the RSCAD software.Through the analysis of the hardware configuration of the RTDS(Real Time Digital Simulator)platform,a multi-coverage was built.A closed-loop test platform for grounding line selection in a fault situation.Through simulation analysis and actual line selection device test,it is found that the theoretical research is basically consistent with the actual experimental results,which proves that the test simulation system built can more accurately imitate the basic lowcurrent system fault conditions,and it provides a reliable way for the line selection device test methods.Finally,in view of the noise interference in the actual distribution network,a composite filter based on the morphological theory is designed to provide a means for signal interference filtering preprocessing.The wavelet transform theory is studied,and its application in the small current system is analyzed to provide a method for transient signal decomposition.Through the analysis of the fault characteristics,a set of singlephase grounding fault line selection criteria and process based on the combination of morphological filtering and transient steady state characteristics are designed,and the effectiveness of the route selection method is verified by case simulation.This paper has 49 figures,10 tables and 91 references.