Study On Simulation And Identification Of Distribution Network Inrush Current

In recent years,when the feeder and its distribution transformers are put into operation,there often appear a power cut accident caused by feeder protection malfunction or power distribution automation unreasonable,seriously influence the power supply reliability of the distribution network.Get into the bottom,the reason is the inrush current in distribution network.It is caused by the magnetizing inrush current that from more than one distribution transformers generate and distribute in the distribution grid.Now,the power protection devices in the distribution network can't correctly distinguish the inrush current and the fault current.However,wave recording devices are not often installed in 10kV distribution network,we can not on-site analysis the inrush current in the distribution network and can't make countermeasures to avoid the power failure has important theoretical value and engineering significance.Therefore,the establishment of the inrush current in distribution grid analysis model and the study of its numerical simulation,then study its identification method has important theoretical value and engineering significance.This paper firstly established a Unified Magnetic Equivalent Circuit model of distribution transformers and deduced that the key in the model to solve the current is how to get the matrix elements of permeability.Secondly,this paper focused on analyzing the processing method of two factors that lead to the inrush current,namely the surge of piecewise linear core saturation calculations,the core reminisce equivalent current source computing.Thirdly,this paper formed a calculation method of transformers in distribution network,write its C language simulation software,and based on the on-site practical parameters of lOkV distributionfeeder and its transformers with practical no-load data of transformers,this paper shows a large number of excitation inrush current waveforms im distribution network under various conditions At the same time,this paper used plenty of PSCAD inrush current waveform verify the validity and accuracy of the research model and simulation analysis software.Then,this paper further studied the identification method of inrush current in distribution network Through deriving a formula to solve the equivalent magnetizing inductance of distribution network?this paper analysis the distribution of magnetizing inductance change rate is different in the occurrence of various types of faults and occurrence of magnetizing inrush current.According to above theory,this paper gave a new identification method and recognition criterion basing on the difference in magnetize inductance,a number of experimental data show that this identification method can effectively and reliably distinguish with inrush current and fault grid current.