Numerical Simulation Of The Winding Temperature Distribution In A Large Oil-immersed Power Transformer Of ODFS-334000/500

Oil-immersed transformer is one of the most important devices in electric power system domestically. The increasing improvement of the voltage level and capacity of the oil-immersed transformer leads to some heat emission problems, such as high hot-spot temperature of the transformer and heat concentrated in the transformer. These problems prevent the transformer from operating safely, thus prevent the power system from transporting stably and safely. Therefore, it is of academic value and practical significance to study the temperature rising characteristics in the oil-immersed transformer, and optimize the oil cooling channel of the winding.In this paper, the commercial CFD software CFX was used to simulate the large capacity as well as high voltage oil-immersed transformer ODFS-334000/500. The research focused on the3D temperature field and internal flow field of the low-voltage and middle-voltage winding.Above all, the low-voltage winding was analyzed comprehensively. Compared with the2D full model, the2D thin-walled model can effectively reduce the amount of the grid. The results show that the average coil temperatures, the hot-spot values and the hot-spot positions of the two models well coincide with each other. Consequently it indicates, the thin-walled model is reasonable to simplify the insulating material inside the transposed conductor.Secondly, the2D thin-walled model and3D thin-walled model of the low-voltage and middle-voltage winding were built. By comparison, it was found that the duct spacers, sticks and circumferential blocks in the3D thin-walled model have blockage effect on the flow. It prevents the oil cooling the winding. The results show that the oil temperature and velocity are not uniform in the circumferential direction, the3D phenomena have been observed in the winding. In the low-voltage, the coil average temperature predicted by the3D thin-walled model is4.756℃higher compared to the2D thin-walled model and the hot-spot value it6.4℃higher. The hot-spot position was also reduced to disc153from the disc168.For fast forecast the temperature distribution characteristic in the winding, the2D thin-walled model was a reasonable simplification of the3D model. In this paper, the oil washer was set in the winding to improve the oil cooling channel in the low-voltage and middle-voltage windings. The2D thin-walled model of the improved model was built to do the simulation. The results show that the coil average temperature and hot-spot value were reduced by7.484℃and5.372℃separately in the improved low-voltage model. In the improved middle-voltage winding model, the coil average temperature was reduced by4.343℃. The improvement effect was very obvious.In this paper, the2D thin-walled models of the other windings were built to do the simulation. The bottom insulation structure of the core center column was built to analyze the3D flow characteristic. The porous resistance coefficients and the volume porosities of the windings and end insulation structure were calculated. The porous model was verified through the low-voltage. At last, the3D simplified porous model of the transformer was built.