Investigation On Temperature Field Calculation On Large Transformer Based On Coupled Multi-physics Method

In power system,power transformer is one of the most important equipments in the power transmission process.The performance of the transformer has great influence on the econmy of power transmission,the flexibility of distribution and the safety of power use.The oilimmersed power transformer has the advantages of good heat dissipation,low loss and large capacity,and is widely used in power transmission and distribution of the system.However,due to the loss of inner core,winding and structural parts in transformer,the transformer will be local overheating,and it will affect the safe operation of transformer when the temperature is too high.In order to more accurately study the distribution characteristics of internal temperature in oil-immersed transformer,it is particularly important to study the electromagnetic field inside transformer,so as to obtain the loss distribution inside transformer.In this paper,the three-dimensional model of large oil-immersed transformer is built according to the actual structural parameters.The electromagnetic field inside the transformer under no-load and rated load conditions is simulated by finite element method.The magnetic induction intensity distribution on the core and the winding is obtained,and the loss on the core and windings is obtained by post-processing.Secondly,the paper studies a method of heterogeneous finite element meshes and interpolation of simulation results,and the method is used to accurately introduce the magnetic field loss obtained by the magnetic field calculation into the corresponding parts of the temperature field model,thus multi-physics coupling simulation of the transformer electromagnetic field,temperature field and flow field is carried out and the calculation results are analyzed by theory.By comparing the calculation results with the experimental results and the conventional calculation methods,the feasibility of the calculation method is proved.Based on the calculation of the internal loss distribution of the transformer,the simulation of the internal temperature and flow field of the transformer is carried out,which improves the accuracy of the calculation model.At the same time,through the research on the temperature and position of the hot spot,it provides some guidance for the structural optimization of the transformer and the temperature measurement of the optical fiber.