A Method Of Fault Line Selection Based On Characteristic Analysis Of Transient Phase-current

The distribution system have low insulation level,complex distribution network structure,changeable operation mode,frequent ground fault(especially the single-phase grounding fault).In modern society,the requirement of power supply reliability is getting higher and higher,and the economic losses caused by the power failure and the bad social impact are also getting bigger and bigger.To study the technology of fault line selection in distribution network,become the urgent demand of the development of intelligent distribution network.Therefore,this paper studied the new method of fault line selection based on characteristic analysis of transient phase-current,is expected can effectively select the fault line when the single phase to earth fault occurs in each type of distribution network.Firstly,the paper describes the existing distribution network fault line selection technology in detail,introduces some advantages and disadvantages of the present domestic and international distribution network fault line selection technology.By comparison,on the whole,the line selection method has a certain effect in certain circumstances,but when ground fault occurs in fault initial angle close to 0° or the high resistance grounding,often leakage judgment,or miscarriage of justice.In view of the disadvantages of the above selection method,the paper based on a detailed analysis of the transient characteristic component of the phase current in the small current grounding fault reaches that,sudden variable of every phase current and the distribution characteristics of phase-current frequency between fault line and non fault lines are significant differences when single-phase grounding fault occurred in neutral indirect ground system.Wave-forms corresponding to sudden variables of fault-phase and non fault phase for fault line are larger differences,and the band that transient signals gather is lower.However,amplitudes of sudden variables of every phase for non fault line are same.Moreover,the wave-forms are also same,and the bands that transient signals gather are higher for fault phase.For this,put forward the comprehensive utilization of the differences between the abrupt change of phase current in the fault line and non fault line and fault phase current signal concentrated frequency band,based on the correlation analysis of the phase current waveform and the fault phase current spectrum analysis,the correlation coefficient of each line and the center frequency of the fault phase are calculated.After normalizing treatment,the fault characteristic coordinate system is established,and the two are effectively combined with the fault feature distance.The two criteria complement each other,which further improves the margin of the line selection.In order to validate the reliability of the fault line protection method,the paper builds a hybrid line distribution network 10 k V model by ATP simulation software.In this paper,the single phase earth fault of different types and different operation modes are tested and simulated.The paper extracts the corresponding data and through the analysis of Matlab on the data processing,draw the line selection results.A lot of simulation and analysis show that the method without fault types,fault resistance,fault initial angle constraints has the advantages of simple operation,high practicability,strong anti-interference ability,etc.Moreover,it is not necessary to set the whole set,which can accurately distinguish the line fault and the busbar fault,and further improve the reliability of the line selection.