Research On Treatment Method And Route Selection Method Of Single-phase Grounding Fault Arc Extinction In Distribution Network

Single-phase grounding faults or related faults caused by them are the most common faults in the operation of distribution networks.In recent years,the capacity of the power distribution system has increased rapidly.When a single-phase ground fault occurs in a neutral point system(NUS),the fault point current increases,and it is increasingly difficult to meet the requirements of self-extinguishing arcs.Arc overvoltage causes damage to electrical equipment;when the neutral point is connected to the arc suppression coil grounding system(NES),when dealing with single-phase grounding faults,it is difficult to meet the accuracy of line selection for high-resistance grounding using traditional line selection methods.The faulty line cannot be eliminated in time,and there is the possibility of the expansion of the accident.Therefore,the key to ensuring the safe operation of the rapidly developing distribution network is to effectively deal with the arc problem when a single-phase ground fault occurs in the NUS system and the line selection problem when the NES system fails.First of all,this article classifies and introduces the neutral grounding methods of the distribution network.Two commonly used grounding methods are selected,the neutral point is not grounded and the neutral point is grounded through the arc suppression coil,and the principle is carried out from two periods of steady state and transient Feature analysis lays the foundation for subsequent simulation results and data analysis.Secondly,the structure and principle of the commonly used arc extinguishing technology in the NUS system are respectively introduced.Based on this,the arc extinguishing technology of the compensation transfer grounding is proposed and its work flow is designed.Design the corresponding fault phase selection scheme according to the different transition resistance of the fault point.For the three arc extinguishing technologies of arc suppression coil,transfer grounding switch,and compensation transfer grounding,numerical calculation models for single-phase stable grounding and arc grounding faults in 10 k V distribution network are established respectively.Set the transition resistance of different fault points,intermittent arc faults of different fault phases,and different outgoing structure fault conditions,and analyze the three arc extinguishing technologies by comparing the fault phase voltage,fault point current,and transfer grounding phase current under each arc extinguishing technology.The arc extinguishing effect of the project has been obtained a conclusion that has reference value for the actual project.Then,taking the new pulse line selection technology as the research object,the composition and working principle of the pulse line selection device are introduced in detail and the flow direction of the pulse current in the NES system is analyzed.Use matlab&simulink simulation platform to build NES system(overhead line system,cable system,cable hybrid system)with pulse signal generator.Under the three systems,set any line to have a single-phase ground fault under different conditions,extract the pulse current of each line for Fourier decomposition,observe the difference in the frequency domain distribution of the pulse current of the faulted line and the nonfaulted line,and propose from each line The sum of the DC and power frequency components decomposed in the frequency domain of the pulse current extracted from the zero sequence current of the line is used as the line selection criterion.By setting the typical fault point position,the fault phase closing phase angle,and the fault point transition resistance as the fault conditions,Verify the accuracy of the line selection criteria.Finally,the working flow chart after the fault occurs when the pulse line selection device and the transfer grounding switch are installed in the NES system.