Analysis And Simulation Research Of Characteristics Of Single-Phase Arc Grounding Fault In Small Current Grounding Power System

The neutral grounding mode of medium and low voltage distribution network usually uses small current grounding mode in China,such as isolated neutral system,neutral earthing via arc extinguishing coil system.The most frequently occurring faults in small current grounding system is single-phase grounding fault,most of which belongs to arc grounding fault.At the same time,single-phase arc grounding fault is often accompanied by a serious electromagnetic transient overvoltage problem,called single-phase arc grounding overvoltage.This high peak over-voltage covers the entire network,which is a serious threat to the insulation safety of the grid.This paper introduces and compares the principle,characteristics and application range of classical ARC models,studies its improved principle and establishes the improved dynamic arc model,and constructs the simulation model of Single-Phase arc grounding fault in distribution network on Simulink software platform.In this paper,a more accurate calculation of the amplitude of single-phase arc grounding over-voltage in asymmetric power grids is proposed,which is advantageous to the system over-voltage protection and the insulation cooperation work.Aiming at the isolated neutral system,the theoretical basis of using capacitive coupling to restrain single-phase arc grounding overvoltage is proposed,which can effectively reduce the over-voltage amplitude and suppress the arc reburning completely,which provides a new theory and measure for solving the single-phase arc grounding overvoltage problem in engineering practice.Based on the neutral earthing via arc extinguishing coil system,lots of single phase arc grounding fault simulation is carried out for the distribution network with different capacitive current size.Combined with the simulation test data,the residual current limit value of the system which makes the grounding fault arc quickly extinguished provides the theoretical reference for the selection of neutral point grounding mode for distributionnetworks with different capacitive current size.Applying the above theory to the distribution network of big citys with isolated neutral system,three-phase voltage asymmetry,amplitude of single-phase arc grounding overvoltage and reasonable overvoltage suppression measures are analyzed in this paper,especially in the condition of isolated neutral system of large city distribution network.It provides the basis for selecting reasonable neutral grounding mode for distribution network of big citys and reducing the potential harm caused by single-phase arc grounding fault.