Research On Coupled Magnetic Fluid-thermal Field Of 2-D Oil-immersed Transformer

Transformer is the important equipment of power system,the operating condition of which is directly related to the stability of the power grid.In actual operation,the temperature of the transformer not only affects the insulation performance but also reduces the service life of the transformer.Transformer multi-physics research has gradually attracted the attention of researchers,with the emergence of various types of transformers problems.Due to the discreteness of the magnetic field distribution on the metal parts of the oil-immersed transformer,the temperature distribution will easily be centralized.This situation further leads to non-uniform temperature distribution in the structure of transformer windings,iron core and steel structures.In order to meet the needs of converter transformer design in HVDC transmission project,the temperature distribution of the transformer needs to be accurately calculated through the coupling of magnetic,fluid and temperature field.Therefore,a reasonable analysis of multi-field coupling has an essential influence on the normal operation of the transformer and even the entire power grid.In order to more accurately predict the location and strength of the hotspot temperature,a multi-physical field hybrid calculation method based on the non-uniform heat source is presented considering the influences of the temperature and the inhomogeneity of Magnetic field loss on the physical parameters of the material.This method adopts the advantages of finite volume and finite element method.The fluid field distribution is calculated using the finite volume method,and the finite element method is used to study the location and strength of the hotspot temperature and the entire temperature distribution of transformer.Non-physical oscillations are effectively avoided by introducing an upwind difference in the solution.Through the data mapping method,magnetic field loss distribution is mapped into the calculation grid of the temperature field,and then the non-uniform heat source of the temperature field is obtained.The proposed method is applied to calculate the temperature distribution and fluid field,and the results of the proposed method are compared with those of software Comsol for two-dimensional simplified model of converter transformer,which proves the accuracy and validity of the proposed method.Based on the validity of the proposed algorithm,the transient temperature distribution of converter transformer during its starting period is analyzed under ambient temperature.The analysis results can be provided as references for engineering practice.