Research On Temperature Field Of Oil-Immersed Transformer And Fluid Influencing On Temperature Rise

Oil-immersed Transformer, the key equipment of the power system, is widely used in various levels of power grid. The reliable safety of the transformer is the guarantee of stable operation of the grid Because the transformer is primary equipment, running environment is bad, especially the heat by loss generated in the transformer seriously affect the service life of the insulation of internal components in the transformer, and even more serious in the performance of large transformer. Winding and iron core inside the forced oil-cycling transformer are cooled by oil flowing driven by pump, but velocity of oil flow is too fast, producing oil flow electrification between oil and insulator, which is not conducive to the safe operation of transformer. Thus, researching on the relation between flow field and temperature distribution is necessary which can be not only effectively controlling internal oil flow rate of transformer, but also better cooling the internal components. The oil flowing in natural oil-cooled transformer is caused by the density change due to temperature, so the velocity of flow is low, producing poor cooling effect. The factors influencing the cooling temperature is complex, studying the effect of structure, external factors such as environment and load on the flow and cooling temperature distribution, plays an important value on improvement of cooling and operation environment.By analyzing the transformer internal heat source, differential equation of numerical calculation of both of forced oil-cooled and natural oil-cooled transformer is established. The solid heat conduction and the convective heat transfer equation on the surface of the solid-liquid interface is given. The method of calculating the convective heat transfer coefficient, and the oil flow within the numerical equations of mass, momentum and energy is established.Two equation of turbulence numerical model of fluid-solid heat coupling in forced oil circulating transformer is established. Temperature field and flow field is calculated by the finite volume, and the relationship between the flow field and temperature field distribution is studied. Further research is done on the inlet flow and the transformer inside the oil duct flow relations, discussing the relationship between the velocity and temperature rise, in-depth analysis of the inlet flow temperature and internal temperature rise of transformer and load coefficient.2-D numerical model of the laminar flow of fluid-solid coupling flow temperature field in nature oil-cooled transformer is created. Three different structure of the model is studied, and the forced flow and temperature field are analyzed. the relationship between oil flow and temperature distribution is given. The comparison of the three kinds of structure (no insulation structure, insulating structure, insulating structure and oil-guide plate) is made on the effect of the temperature rise and oil flow. The factors affecting temperature such as load, the height of the radiator, the radial oil duct height, environmental temperature on the internal temperature of transformer are also studied.