Analysis Of The Structural Part Loss And Local Overheating In Power Transformer

The research on experimental research and numerical simulation of stray-field losses in electrical equipment is a complex and classic problem. Taking the large power transformer as an example, the stray-field loss of it is generated by leakage magnetic field in the conductive entity or laminated components. The distribution of stray-field loss, the position of hot spots and shielding effects become three important problems for transformer research, development and design. The large transformer capability increases, causing the strength of leakage field increases, and the eddy current loss increases, resulting in local overheating problem more serious. Therefore, it is critical to analyze eddy current loss.Firstly, this thesis introduces the development situation of domestic and international researches on power transformer magnetic field and temperature rise, and discusses the meaning and purpose for calculation of eddy current field and temperature field. At the same time, aiming at the difficulties of the project studied in this thesis, the solutions and hypotheses are given. The simulations of leakage magnetic field and temperature field of power transformer are carried out using the commercial software ANSYS with its three-dimensional finite element (FE) analysis module, based on the essential theory of FE combined with the strategy of divisionally assigned permeability. The 3D-FE analysis model of the power transformer is established first, then the distribution of the magnetic flux densities and eddy current densities in the structural parts of the transformer are obtained through calculations. Based on these computations, the discussion of the method to decrease the leakage magnetic field, eddy current losses, so as to decrease local overheating are developed in the aspects of the relation of stray loss in iron core and the "minimal level" configuration, stray loss in oil tank and the magnetic and electromagnetic shielding configuration, and stray loss in the pulling plate and camping unit and their configuration.At last, take the eddy current losses in the form of heat generation rate as the load of temperature field to solve the coupling problem of magnetic field and temperature field, on the basis of calculated results of eddy current densities for each structural parts in the transformer. Then the distribution of temperature inside the transformer is obtained, which is generated by the quantity of heat resulting from the leakage magnetic field, and the location of hot spots is analyzed.