The Calculation Research Of Temperature Rise Of Large Natural Oil Circulation Power Transformer With Directed Structure With The Means Of Natural Air Cooling And Forced Air Cooling

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 widely used in large power transformer.The temperature difference between copper and oil of natural oil circulation power transformer is bigger than that of forced oil circulation. The calculation method used in factory has larger error and doesn't properly act in accord with practical temperature rise.In this paper a calculation method, which has been verified by experimental results, is set up based on the fundamental theories and rule equation of heat transfer to calculate the temperature rise of average oil, top oil, coil. Some of the main factors ,such as total loss,the position of radiators, the radial width of winding and heat flux of winding ,are analysed to influence temperature rise of transformer. This method is suitable for natural oil power transformer with directed circulation with the means of natural air cooling and forced air cooling.In this article geometrical parameters of radiators such as center distance , the number, the width , the thickness of radiators , which have effects on the heat transfer, are considered based on the structure characteristic of radiator and the theory of heat transfer.As a result of different cooling characteristic of ONAF an ONAN.different rule equations of heat transfer are chosen according to the actual instance and the effects of fans are taken into accounts. Because of the directed structure, the velocity of oil in vertical and horizontal ducts is analyzed and the number of directed regions and oil ducts,the average height of horizontal duct are related to the oil velocity.Software that can be directly used by users is written in this paper. This software is easy to use and has a strong data processing function. The calculating results are quite identical to the results of the average temperature of experiment. This method can meet the demands of the project.