Study On Differential Protection Of Transformer And Inrush Current Identification

Power transformers are important power equipment,in the practical application,requiring power transformers and other electrical equipment for long time continuous operation,which inevitably induces power transformers and other electrical equipment failure and accidents.When it fails,it not only endangers the safety of the power grid,but also seriously causes great economic property damage.Therefore,in order to monitor the interior operation of the transformer,real-time and accurate to identify the latent faults of the transformer,it is necessary to take reasonable and effective protective measures.The most urgent problem the transformer differential protection needing to solve is how to accurately identify the problem of excitation inrush current and internal fault current.This paper is based on the related research and analysis,and gives a new identification method.In addition,for the microcomputer protection device of the transformer,this paper puts forward a protection design of the hardware and software based on the embedded technology.The main contents of the article are as follows:Firstly,the background and significance of transformer longitudinal differential protection are introduced and studied,and the important points of longitudinal differential protection are analyzed theoretically;Secondly,the basic principle of transformer longitudinal differential protection,the characteristics of excitation inrush current and several criteria for identifying the excitation inrush current are often used in the study.At the same time,the criterion and algorithm of the differential protection of the transformer are studied and analyzed.Then,the theory of phase space reconstruction is introduced in detail.Based on this,three geometric invariants(correlation dimension,Kolmogorov entropy and Lyapunov index)are used to identify the transformer excitation inrush current and internal short-circuit fault current.In addition,the model and framework of the excitation inrush current and internal short-circuit fault current of transformer are set up by MATLAB/SIMULINK software.The simulation experiment is carried out according to the running condition of the transformer under different conditions,and the differences between the waveform and data in the simulation of the excitation inrush current and internal short-circuit fault current are studied emphatically.Finally,some hardware modules of the transformer relay protection device based on TMS320F28335DSP are given,and some main software design flow charts are given for the hardware design part.