第二代高温超导股线的过流及机械特性研究

发布时间：2018-10-14 19:45

【摘要】：高温超导材料在性能上的改善,使超导体在工程领域的应用得到高速发展。本文提出一种各向同性的高温超导股线设计方法,能够进一步增强超导体的载流能力,提高超导填充度和工程电流密度,改善超导结构的机械强度,可以运用在直流输电电缆、高场磁体、超导限流器等电力装置,具有广阔的应用前景。本文首先介绍圆形和方形高温超导股线的设计方法,阐明超导股线芯的带材堆叠方式,对填充超导芯与包套间缝隙的结构进行材料选择与规格设计,介绍金属包覆层的激光焊接工艺,分步阐述铜、铝和不锈钢包覆的超导股线规模化生产流程。为验证超导股线加工工艺的安全性,将完成制作的股线样品拆解并对超导芯部分的ReBCO带材进行临界电流测试。实验结果表明,在高温超导股线的制作过程中不会对内部带材造成损伤。用磁场仿真软件建立不同超导股线的横截面二维模型,根据磁场仿真结果计算超导股线的临界电流值,对不同结构的股线样品进行临界电流测试,从测量结果中提取体现超导特性的E-I曲线,实验结果验证临界电流仿真计算模型的有效性,为未来不同材料和规格的高温超导股线设计提供依据。实验研究77 K、自场下高温超导股线在工频过电流冲击下的失超及恢复特性,分析冲击过程中电压及电流幅值变化原因、电阻及相位角变化规律,研究冲击电流对不同类型股线的温升和恢复时间影响,通过冲击后的临界电流和n值测量结果分析超导股线的耐冲击能力。实验结果表明,不同结构的超导股线在冲击过程中的失超特性不同,铜包覆超导股线具有较强的耐电流冲击能力,不锈钢包覆超导股线则具有较强的电流限制能力。研究高温超导股线的机械特性,对弯曲的超导股线中带材形变情况进行理论分析,并制作不同弯曲条件下的ReBCO带材和超导股线实验样品,通过临界电流的测试研究弯曲对载流能力产生的影响,分析带材最小侧向弯曲半径、超导股线的最小弯曲半径及临界应变等参数,通过测量股线样品在不同拉伸应力条件下的临界电流和n值,研究拉伸应力对超导特性的影响。研究结果表明,超导股线的最小弯曲半径由带材的侧向弯曲特性决定,且临界电流和n值随弯曲半径减少或拉伸应力的增大呈降低趋势。
[Abstract]:With the improvement of the properties of HTS materials, the applications of superconductors in engineering field have been developed rapidly. In this paper, an isotropic design method of high temperature superconducting strands is presented, which can further enhance the current carrying capacity of superconductors, increase the superconducting filling degree and engineering current density, improve the mechanical strength of superconducting structures, and can be used in DC transmission cables. High-field magnets, superconducting current limiter and other power devices have a broad application prospects. In this paper, the design method of circular and square high temperature superconducting strands is introduced, and the strip stacking mode of superconducting wire core is expounded. The material selection and specification design of the structure filled with the gap between the superconducting core and the package sleeve are carried out. The laser welding process of metal coated layer is introduced, and the large-scale production process of superconducting wire coated with copper, aluminum and stainless steel is described step by step. In order to verify the safety of the superconducting wire processing process, the finished strands were disassembled and the critical current of the ReBCO strip in the superconducting core was measured. The experimental results show that the inner strip will not be damaged during the fabrication of HTS strands. The two-dimensional model of cross section of different superconducting strands was established by using magnetic field simulation software. According to the results of magnetic field simulation, the critical current of superconducting strands was calculated, and the critical current of samples with different structures was measured. The E-I curves reflecting the superconducting characteristics are extracted from the measured results. The experimental results verify the validity of the critical current simulation model and provide the basis for the design of HTS strands of different materials and specifications in the future. The overrun and recovery characteristics of high temperature superconducting wire (HTS) strands under power frequency overcurrent impact at 77K are studied experimentally. The causes of voltage and current amplitudes during shock, the variation of resistance and phase angle are analyzed. The effect of shock current on temperature rise and recovery time of different types of strands was studied. The shock resistance of superconducting strands was analyzed by measuring critical current and n value after shock. The experimental results show that the superconducting strands with different structures have different overshoot characteristics during impact. Copper coated superconducting strands have strong current shock resistance, while stainless steel coated superconducting strands have strong current limiting capacity. The mechanical properties of high temperature superconducting strands are studied. The deformation of tapes in bending superconducting strands is theoretically analyzed, and the experimental samples of ReBCO tapes and superconducting strands under different bending conditions are made. The influence of bending on the current carrying capacity is studied by measuring the critical current. The parameters such as the minimum lateral bending radius of strip, the minimum bending radius of superconducting strands and the critical strain are analyzed. The influence of tensile stress on superconductivity was studied by measuring the critical current and n value of the strands under different tensile stress conditions. The results show that the minimum bending radius of the superconducting strand is determined by the lateral bending characteristics of the strip, and the critical current and n value decrease with the decrease of the bending radius or the increase of the tensile stress.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM26

【参考文献】