Research Leakage Magnetic Field And Analyze Winding Temperature Field For Power Transformer

At present, China’s electricity demand is increasing, with the increase of electric power transformer capacity; the influence of transformer internal leakage magnetic field for the structural component also increases significantly. The structural component often appears local overheating by eddy current concentration that can speed up the normal aging process of the insulating material. It will affect the service life of the transformer, and the safe operation of the power grid will be threatened. So the further study of a large power transformer leakage magnetic field and temperature field is becoming very important.In this dissertation, the research on a three-phase five pillar of large power transformer. The leakage magnetic fields are analyzed in the high-medium rated operation conditions. Due to the transformer with axial symmetry structure, finite element method is adopted to establish the half calculation model of2-D leakage magnetic field. By the calculation, the distribution of2-D leakage magnetic line is received. In order to analyze the magnetic field distribution of core and windings in different time, establish three dimensional calculations model. At the same time, the axial and radial leakage magnetic field of the winding are separately extracted, and its distribution is analyzed. In addition to the eddy current loss density distribution of the tank and the value of eddy current loss of the winding are calculated. Based on the analysis results of leakage magnetic field, the dissertation gives a method to reduce leakage magnetic field and eddy current loss. Analyze the effect of magnetic shielding on the tank wall, and contrast effect of the different shield size by changing the width and height of the shield, get the best scheme of technical index and economic index.Then the dissertation analyzes the winding temperature, winding heat mainly comes from the electrical loss, and a small part of the heat comes from the eddy current loss, the eddy current loss part accounted for9.41%of total winding loss, all the heat are coupled to the temperature field calculation. It adopts the method of fluid-structure interaction to calculate steady temperature field and fluid field for the winding and oil of transformer. Finally the temperature distribution of winding and velocity distribution of transformer oil are get by calculating. Through analyzing the calculation results of temperature field, the design scheme of improving the winding hot spot temperature and the distribution of oil flow is given. The main content of the dissertation provides theoretical basis for improving local overheating of transformer that can make better service to the practical engineering application.