Simulation And Analysis Of Winding Fault Of Dry-type Transformer Based On Fractional Order Model

With the increasing scale of modern power systems,there are also higher requirements for the safe and stable operation of the power system.As an important component in the power system,the normal operation of the transformer is related to the safe operation of the entire power grid.Especially in modern power systems,the requirements for transformers are getting higher and higher.Traditional oil-immersed transformers have many insurmountable problems,but the advantages of dry-type transformers are increasingly obvious.In order to ensure the safe operation of the power system and to ensure that the transformer can be identified and acted quickly and accurately when the transformer fails,it is necessary to analyze and research various faults of the transformer.Based on the theory of fractional calculus,this paper uses the improved Oustaloup filter algorithm to complete the mathematical realization of the fractional operator,and analyzes the internal faults,magnetizing inrush current and temperature field of dry-type transformers.The fractional mathematical model of dry-type transformer is established,and several common internal faults of dry-type transformer are simulated and analyzed.Based on the fractional Fourier transform theory,a new method of inrush current identification is proposed.The fractional thermal circuit model of dry-type transformer is built,and the temperature distribution of dry-type transformer is obtained by simulation.The main work and innovations of these paper are as follows:1)Fractional-order model of dry-type transformer.In this paper,based on the fractional physical characteristics of actual inductance,the fractional operator is introduced into the mathematical model of dry-type transformer,and the fractional simulation model is established by improved Oustaloup filtering algorithm.The simulation model is changed by the change of winding after transformer failure,and the ground fault,turn-to-turn fault and phase-to-phase fault of dry-type transformer are simulated and analyzed.The simulation results are compared with the integer-order model,and the accuracy and precision of the fractional model are verified.2)Identification method of transformer magnetizing inrush current.Based on the theory of fractional Fourier transform,this paper proposes a new method of using fractional Fourier transform to identify the magnetizing inrush current.Firstly,the optimal order of fractional Fourier transform is searched for the transformed waveform,and then the optimal order is used to perform fractional Fourier transform on the waveform.The transformer inrush current and turn-to-turn fault waveform are respectively subjected to fractional Fourier transform,and the two can be accurately distinguished by the transformed frequency peak value.3)Fractional thermal circuit model of dry-type transformer.Based on thermoelectric analogy theory,the core,high and low voltage windings and air duct of the transformer are regarded as several nodes,and each node is connected by thermal resistance and heat capacity under different heat exchange modes.The thermal circuit model of dry-type transformer is established by layers.Based on the fact that capacitor elements are actually fractional components,the fractional thermal circuit model of dry-type transformer is proposed.4)Solution of fractional temperature conservation equation of dry-type transformer.In this paper,the temperature conservation equation of the dry-type transformer is obtained by the thermal circuit model,and the prediction equation and correction equation of the fractional differential equation system are obtained by the prediction-correction method,which are solved by programming in Matlab to obtain the average temperature of each part of the dry-type transformer.