Research On Single-Phase Ground Fault Line Selection Method In Distribution Network Based On Fault Type

With the development of economy and the continuous construction of cities,the structure of distribution network is becoming more and more complex.In order to ensure the reliability of power supply,it is necessary to eliminate faults timely and accurately.In China,the distribution network is mostly grounded with small current,and single-phase ground fault is the most frequent fault in the system,so the problem of single-phase ground fault line selection is very important.In recent years,experts and scholars have proposed many methods of line selection,but most of the traditional methods are difficult to ensure the reliability of line selection for different types of faults when disturbed by various external factors.Therefore,it is necessary to conduct in-depth research on the selection of different types of ground faults.Based on the analysis of steady-state and transient characteristics of single-phase ground fault in small current system,this paper focuses on the change of steady-state and transient zero-sequence current.Through the classification of fault types,the characteristics of metal grounding,high resistance grounding,arc grounding and intermittent arc grounding are analyzed respectively.Based on the theory of arc gap energy balance,a practical arc model is established.At the same time,the validity of the fault model selected in this paper is verified by simulation analysis of different types of fault models.This paper classifies the existing line selection methods according to the different characteristic components used in line selection,analyses the advantages and disadvantages of each method and its application scope,and determines the line selection method in this paper,that is,using the excellent characteristics of mathematical morphological analysis in signal processing,designing a reasonable morphological filter to extract fault transient characteristics,and combining with the analysis of fault process,a method of fault line selection based on morphological analysis of fault process is established.Finally,a 35 kV low current grounding system with five feeders is designed,and the model is built in PSCAD.Then,the method of selecting different types of grounding faults is used to simulate and verify the selection of different types of grounding faults.Through a series of simulation experiments,it is shown that for different types of grounding faults,the proposed method can achieve reliable and accurate fault line selection.