Research On Arc High Resistance Grounding Fault Disposal Method Based On Flexible Grounding Distribution Network

Flexible grounding distribution network combines the advantages of arc suppression coil grounding system and low resistance grounding system,and gives full play to the advantages of arc suppression coil overcompensation and arc grounding overvoltage suppression by small resistance.Therefore,it has been applied in the distribution network of our country.However,when the arc high resistance grounding fault occurs in the line,the input of the parallel small resistance can have an impact on the distribution system,and cannot achieve the purpose of putting in the small resistance,that is,the ineffective input of the parallel small resistance.If the fault line cannot be removed for a long time,it may cause serious harm to the distribution system,so when the arc high resistance grounding fault occurs in the flexible grounding distribution network,the research on how to make correct fault disposal measures is of great significance to quickly restore the power supply of the system,reduce unnecessary economic losses and the development,safety and reliable operation of the distribution network.First of all,based on the zero-sequence equivalent circuit of single-phase-toground fault in flexible grounded distribution network,this thesis analyzes the phase relationship between zero-sequence current at the head of each line and non-fault phase line voltage before and after the input of neutral shunt small resistance after a permanent single-phase-to-ground fault occurs in the flexible grounded distribution network.Thus,a fault line selection method for flexible grounding distribution network is proposed based on the phase difference between zero sequence current at the head of each line and non-fault phase line voltage after parallel small resistance is put into operation.The simulation results using PSCAD verify the effectiveness and reliability of the proposed fault line selection method.Secondly,based on the improved cybernetics arc model,three common scenarios are considered simultaneously to establish the corresponding arc grounding fault model and the corresponding mathematical expressions are given,including indoor stable arc fault model,outdoor unstable arc fault model,and overhead line transient arc fault model.Then,based on the proposed arc grounding fault model,two different fault transition resistance estimation methods are proposed from two aspects: the known line parameters and the unknown line parameters.The simulation results using PSCAD verify the reasonable accuracy of the arc grounding fault model and the effectiveness and engineering practicability of the proposed fault transition resistance estimation method.Finally,based on the proposed fault transition resistance estimation method and fault line selection method for flexible grounding distribution network,a highly sensitive fault disposal method for flexible grounding distribution network is proposed,which is suitable for arc high resistance grounding fault,and the specific implementation process of fault disposal is introduced in detail.The joint simulation is carried out by using PSCAD and MATLAB,in which the simulation arc model adopts the established arc grounding fault model.The simulation results verify the effectiveness and reliability of the proposed fault disposal method.The method has high sensitivity,can improve the withstand fault transition resistance ability of line protection,and effectively reduce the invalid input times of parallel small resistors.There are 45 figures,8 tables and 81 references in this thesis.