The Calculation Research Of Temperature Field Of Large Natural Oil Circulation Power Transformer With Oriented Cooling Structure

Oil immersed transformer is widely used in power transmission because of its good coolant, low wastage and price, large capacity. At present, in oil immersed transformers natural oil circulation is used at about 80%. In order to solve the noise-disturbing-citizen problem and remove the static electricity in oil flow, natural oil circulation has been wildly used in large power transformer. A direct result of adopting natural oil circulation is to increase the temperature difference between copper and oil. So the heat elimination becomes more serious. At present, the research about thermal performance of large natural oil circulation transformer is relatively little at home and abroad. It is high time that a convenient and effective method which predicts the value and the position of the hottest-spot was set up.This paper sets up a kind of method to calculate the temperature field of the winding in large natural circulation power transformer with oriented cooling structure. This method has convenient and effective characteristics. Program written with this method has strong versatility and is easy to use.This paper sets up the mathematic model of heat transfer and oil flow, and finishes the calculation of oil flow distribution and temperature field of winding in large natural oil circulation power transformer with oriented cooling structure. The work of this paper will offer reliable reference data which can guide the design and the operation of the transformer and help improving the transformer design. In this paper, oil flow is described as one-dimension flow, and calculated with Newton-Raphson method. According to the characteristic of the power transformer, the temperature field of winding can be described with a partial differential equation in a cylinder coordinate system. It is calculated with finite difference method. Finally, the value and the position of the hottest-spot are found.Program is written in C++ language and MATLAB language to finish the calculation of the temperature field of winding. Finally, the position and the value of the hottest-spot are found. This program is suitable for natural oil oriented circulation transformer. This program is not restricted by the number of ducts and oriented areas in windings and the size of duct and winding. It is not restricted by the number of windings in transformer either.Software that can be used directly by users is written in this paper. This software is easy to use and has a strong data processing function. Final result of calculation can offer users reliable and convenient reference to analyze the thermal performance of transformer. The calculating results are quite identical to the results of the average temperature of winding test. This method can meet the demands of the project.