Electromagnetic Design And Preliminary Stability Study Of MVA Superconducting Coated Conductor Transforming Winding

Compared to regular power transformer, superconducting coated conductor transformer has the advantages of small volume, light weight, high efficiency, strong capability of overload and no risk of fire, since the superconducting transformer replaces the copper winding of regular power transformer with superconducting tapes, during the grid-connected operation, once the superconducting winding has problem, it may play a role in limiting fault current to supply the electricity and influence the stability of the entire electric power system. Therefore, superconducting transformer is one of the key technologies in the power system.This thesis focuses on the problems that needed to be considered in the designing of superconducting transformer windings, core cable is applied in MVA superconducting transformer, and we will mainly study on three aspects of the design and current-carrying features of the core cable, electromagnetic design of superconducting transformer winding and the stability of the superconducting windings to lay the foundation for the subsequent development of the prototype superconducting transformer.First of all, establish the equivalent mathematical model of core cable according to the structural features, use the analytic method to figure out the calculation formulas of the self inductance and mutual inductance of the core cable, and increase core cable ampacity by adjusting the structural parameters. By using the software of COMSOL Multiphysics4.4 to carry on modeling and simulation and analyze the law of changing of the intensity of magnetic field in the lower conductor layer under different structural parameters so as to reduce the influence of magnetic field on the current-carrying of the conductor layer. Short core cable and experimental platform are made. Analyze the change of current-carrying features of the core cable along with the extra magnetic field and the critical current degradation curve of the core cable in different winding radiuses through experiments to lay the ground work for the electromagnetic design of the MVA superconducting transformer winding.Secondly, accord to the main performance parameters of 25MVA,110kV/10.5 kVsuperconducting transformer, carry on the preliminary design of the superconducting transformer. It establishes the basic arrangement and configuration of the windings.Use the software of COMSOL Multiphysics4.4 to establish the structural modeling of superconducting transformer, have the coupling calculation of "circuit-magnetic field", analyze the magnetic field in the superconducting transformer winding area, point out the methods of reducing the radial component of leakage magnetic field and realize the optimal design of transformer winding by changing magnetic permeability of the sub-ring.Finally, the thesis will have the simulation experiment on the stability of the superconducting winding to analyze the law of curves on the change of temperature and voltage in the condition of quenching in different thermal disturbance. Combine the stability theory to estimate the quench propagation velocity, and analyzes the factors affecting the quench propagation. High substrate coated conductor production, cooling channels and high conductivity oxide powder hybrid resin impregnated could be used in the high-voltage winding to raise stability. However, the quench propagation speed of the low voltage windings is slower, it is convenient to condition monitoring and fault diagnosis of superconducting transformers.