Analysis Of Leakage Magnetic Field For Three-phase High Temperature Superconducting Transformer

For modern power transformer, it is a kind of electric power equipment with high reliability and high efficiency. However, with the rapid development of urban construction in our country, both of the power industry and technology related to transformer have also made rapid development, and all the development has been increasing the requirement of transformer technology gradually. Nowadays, the power transofrmer needs to meet the requirements of miniaturization, low noise and oil-free, in addition to meet the requirements about electrical, magnetic, mechanical, heat, high efficiency and so on. And its purpose is to cut down the occupied space, reduce the possibility of danger, and decrease environmental pollution. Compared with high temperature superconducting transformer, traditional transformer cannot meet the needs of the development of modern electric power industry, especially the inevitable shortcomings.High temperature superconducting transfoemer has some advantages, such as small volume, light weight, good environmental performance, high security, energy saving etc, so it is suitable for high power density and large capacity. It can also be used as a connecting device to connect conventional electric power equipment or other superconducting electrical power equipment. Due to the high density of current-carrying superconducting tape and anisotropy, magnetic flux leakage problem seems to be a major issue for superconducting tape. The existence of leakage magentic field of high temperature superconducting transformer can reduce the current-carrying capacity of transformer winding, increase AC losses. At the same time it also influences the electromagnetic force on winding both in the normal and fault conditions, even makes superconducting windings deformed or damaged. Therefore, it is necessary to reduce the leakage magnetic field of superconducting transformer.Firstly, the high temperature superconducting transformer and its advantages are briefly introduced in this dissertation, and the development of superconducting transformer leakage magetic field and current reasearch status are analysed.Secondly, on the basis of the electromagntic theory analysis of high temperature superconducting transformer, the 1250 kVA three-phase high temperature superconducting transformer is took as the research object,and the object model is built and the leakage magnteic filed is analysed by using finite element analysis software Ansoft Maxwel. Then, the magnetic induction intensity distribution cloud and radial componet of leakage magnetic field on the path curve are got.Thirdly, in order to reduce the leakage magnetic field, leakage magnetic field of superconducting transformer with different winding structure is analysed by using finite element analysis software Ansoft Maxwell. It includes unequal air gap winding structure, split winding structure, step type winding structure of the auxiliary winding leakage magnetic field analysis of different schemes. Magnetic induction intensity distribution can be drawn from cloud and radial component of leakage magnetic field on the path curve.Finally, through the analysis of the advantages and disadvantages of different winding structure schemes, more appropriate selection schemes are given. And it provides a reference basis for high temperature superconducting transformer electromagnetic design, optimization and improvement aspect of winding.