Analysis On Eddy Current Loss Of Metal Structure And Thermal Field Of Power Transformer

Power transformer is one of the important electrical equipments in powertransmission which is very significant for the stability of electric energytransmission, the rationality of its distribution, the security of using and theeconomy of operation in power system. The eddy current loss of metal structureand its local overheating problem of the power transformer have aroused greatattention of people. With the increasing capacity of the transformer, the leakagemagnetic field intensity becomes much stronger and the eddy current loss ofmetal structure which was caused by the leakage magnetic becomes much greater,which may cause the local overheating of metal structure and affect theoperational stability of transformer. Therefore, in-depth research on thetemperature field and the eddy current loss of metal structure of the transformerhas an important significance.The basic theory of electromagnetic field and the reason of transformer’sleakage magnetic field and its effects are introduced in the beginning of thisthesis. In the second place, the mathematical and physical models are establishedto solve the three-dimensional leakage magnetic field of transformer, and thefinite element method is used to calculate the leakage magnetic field distributionin quasi-stable field, on the base of the conclusion, the eddy current lossdistribution of metal structure is calculated. After that, through the calculationand analysis of the eddy current loss distribution of metal structure in differentsituations, such as installing magnetic shielding on the oil tank wall and clamp,slotting on the tie-plate and so on, some measures to reduce the eddy current lossof metal structure are provided. Finally, the model of solving the two-dimensional thermal and fluid field is established by the FLUENT software basedon heat transfer and hydromechanics theory, and thermal and velocity fielddistributions of different spots in the internal of transformer are obtained; the influence of different center heights of radiator on the thermal and velocity of thefluid in the transformer is compared and analyzed, and the method of reducingtemperature of transformer are proposed.By the calculation and analysis on the leakage magnetic field, the eddycurrent loss of metal structure and the thermal field of power transformer, thethesis obtains that the eddy current loss of metal structure can be decreased byinstalling magnetic shielding and slotting on the tie-plate, and the temperature oftransformer can be reduced effectively by raising the center height of radiator,which provides evidence and has definite instructive significance to theengineering design of power transformer.