Research On Single Phase Are Grounding Fault Characteristics Of Distribution Network

With the rapid development of China’s distribution network,large-capacity distribution networks with ungrounded neutral points,mainly cable lines,widely exist,so the capacitance current to ground is increasing,which directly leads to the frequent occurrence of single-phase grounding faults in distribution systems and is difficult to avoid.Generally,this kind of fault has weak destructive power and low arc energy,so if the arc can be eliminated in time,most of these faults can achieve “self-healing”.However,if the arc is not extinguished in time after a fault occurs,the insulation of the distribution line may be damaged,and even short-circuit fault may be caused to the whole distribution system,thus damaging the safety,stability and reliability of the distribution system.Studying and analyzing the characteristics of single-phase arc grounding fault is of great significance for fault location and removal,which is conducive to improving the stable operation ability of power grid system.Firstly,this paper analyzes the causes and development process of single-phase arc grounding fault,and expounds the generation mechanism of arc overvoltage by using the theory of power frequency arc extinguishing.Secondly,aiming at the limitations of the classical arc model Cassie model and Mayr model,such as complex modeling and poor applicability,a new fault arc model is established by using ATP-EMTP software,which can estimate and fine-tune the parameters according to the arc occurrence.The simulation results show that it is closer to the theoretical and engineering practice and more practical.The simulation model of small current grounding system with arc process is established,and the influence of different fault conditions on steady-state and transient voltage,current amplitude and phase characteristics of fault is comprehensively simulated.After a singlephase grounding fault occurs in distribution network,the transient zero-sequence current waveforms between non-fault lines are similar,but the transient zero-sequence current waveforms of fault lines are quite different from those of non-fault lines.Therefore,a small current grounding line selection method based on grey theory is proposed and verified.Finally,in order to explore the real fault characteristics in the field,a simulated grounding test is carried out on the 10 k V line,and the field fault recording is provided.The characteristics of its electrical parameters are basically consistent with the simulation results.These theoretical and technical results studied in this paper can be directly applied in practical engineering,contributing to further research on arc-earth faults and providing a sufficient theoretical basis for the selection and location of small-current single-phase ground faults.