Three Dimensional Magnetic-fluid-temperature Coupling Simulation Of 35kV Natural Oil Circulation Transformer

With the successive introduction of the "14th Five-Year" State Grid and China Southern Power Grid development plans,a new round of power grid construction is in full swing.Transformers are the core components of the power system.Among them,oil-immersed power transformers have the characteristics of strong heat dissipation,wide adaptability and low cost.The abnormal temperature rise and high hot spot temperature inside the transformer will seriously threaten its service life and stable operation.Therefore,it is of great significance to study the temperature rise characteristics and hot spot distribution inside the transformer.In this paper,a 35 kV double-winding oil-immersed transformer is taken as the research object,and its internal oil flow characteristics and temperature rise are studied through three-dimensional magneto-fluid-temperature multiphysics coupling simulation.The specific work is as follows:Firstly,based on the numerical calculation principle of electromagnetic field and the analysis of transformer loss characteristics,a three-dimensional transformer magnetic field simulation model is established,and the time-harmonic field method is used to simulate the no-load and load loss of the transformer.The magnetic field distribution of the transformer core and its loss value are obtained from the no-load loss calculation model,and the leakage flux distribution and load loss in the winding area are obtained from the load loss model,which provides a heat source for multi-physics coupling.The factory test was compared to verify the validity of the calculation results.Secondly,based on the theory of porous medium and equivalent thermal conductivity,the simulation model of the temperature field of the transformer’s high and low voltage windings is simplified,and a 35 kV three-dimensional magneto-fluid-temperature coupling simulation model is established.Based on the coupled simulation analysis,the oil flow distribution characteristics of the transformer and the distribution of temperature rise and hot spots are obtained.Finally,based on the Raman scattering distributed optical fiber sensing temperature measurement platform for transformer temperature rise,the temperature rise test of 35 kV transformer was studied.The winding temperature distribution obtained by the multi-field coupling simulation is compared with the full-time temperature results obtained by the distributed optical fiber measurement.At the same time,considering the temperature nonlinearity of transformer loss,UDF is used to correct the loss value of fluid temperature field,and the influence of temperature nonlinearity of loss on temperature rise and hot spot distribution is studied,and the error caused by experimental and simulation results is discussed.This verifies the effectiveness of the coupling method proposed in this paper.