Analysis And Calculation Of Leakage Magnetic Field And Reactance Parameters Of Power Transformer

The electromagnetic design of power transformer is closely related to the leakage magnetic field of transformer.The larger the capacity of transformer is,the stronger the leakage magnetic field is,thus various supplementary load losses incurred by the steady leakage magnetic field increase.The improper design will cause the local overheating of the transformer,which indicates the depravation of transformer's performance,finally causing the insulation breakdown.In the short circuit of electric power system,the leakage magnetic field generated by transient short circuit current could also generate a great mechanical force which causes the deadly threat to the insulation and mechanical structure.For the purpose of alleviating the influence of leakage magnetic field in the above condition,it is necessary to analyze the leakage magnetic field generated in the normal operation and short circuit operation.In order to reduce the impact of leakage magnetic field on the operation characteristics of transformer,this thesis,starting from the analysis of three dimensional magnetic field of power transformer,conducts the modeling to the power transformer in ANSYS/Maxwll software as per the design principle of transformer.Firstly,the 3D simulation model and coupling external incentives are established with the 240000kVA/550 kV single-phase power transformer as the research object to design and calculate the short circuit reactance parameters and inductance parameter of transformer windings,and the distribution law of leakage magnetic field is analyzed under the short-circuit status and the normal operation in the finite element method.Secondly,the reactance parameter is modeled for the high voltage winding,intermediate-voltage winding and low voltage winding,respectively,with the 150000kVA/220 kV three-phase power transformer as the research object.The distribution of three-dimensional leakage magnetic field and the winding current are calculated under the secondary side short circuit state,the short circuit reactance parameter is also calculated,and the calculation results are compared and analyzed.Finally,the calculated reactance and various parameters are led to MATLAB for simulation,and the single-phase and three-phase power transformer are analyzed under no-load and short circuit,as a result,the waveform analyzed in the finite element is consistent with the result.Based on the simulation and analysis results of two sets of power transformers,the three-dimensional field could simulate the actual operation status of transformer better in thecalculation of leakage magnetic field of transformer,and the parameter design of transformer is guided better;In the meantime,the simulation result of MATLAB is analyzed to verify the correctness and rationality of parameter calculation.