Development of High Performance Extruded Polymer Insulated DC Superconducting Model Cable using High Temperature Superconductor

研究人员一直在开发挤出式乙丙橡胶（EPR）绝缘超导电缆。本研究开发的模型电缆结构非常简单：将银包铋型高温超导导线平行敷设在稳定芯黄铜管上，采用包覆EPR和半导体屏蔽层进行电绝缘。在室温-液氮温度（77K）之间反复热循环后，对芯管上超导导线的布置进行优化，使其与EPR绝缘良好接触。这表明EPR在冷却时的径向、周向和长向热收缩对超导导线的电流特性没有影响。因此，EPR绝缘可以应用于高温超导体，而高温超导体通常被认为容易受到机械应力的影响。直流临界电流和熄灭电流的测量也表明，它们仅受包裹EPR绝缘的机械应力的轻微影响。划时代的事实是，直流超导电缆可以消除与交流电缆相关的所有损耗和缺点：迟滞损耗、涡流损耗、绝缘的介电损耗和局部放电。因此，本研究结果为直流高温超导电缆在未来地下输电中发挥主导作用开辟了道路。

The investigators have been developing extruded ethylene-propylene rubber (EPR) insulated superconducting power cables. The model cable developed in this study had very simple structure : the silver sheathed bismuth type high temperature superconducting wires laid in parallel on a stabilizing core brass pipe is electrically insulated by wrapped EPR together with semiconducting shielding layers. The optimization of the layout of the superconducting wires on the core pipe gave their satisfactory contact with EPR insulation after repeated thermal cycles between room temperature (RT) and liquid nitrogen temperature (77K). This reveals that the radial, circumferential and length-wise thermal contractions of EPR at cooling do not affect the current characteristics of the superconducting wires. Hence the EPR insulation can be applied to the high temperature superconductors who are generally considered to be vulnerable to the mechanical stress. The dc critical current and quench current measurements also showed that they are only slightly affected by the mechanical stresses of the wrapped EPR insulation. The epoch-making fact is that DC superconducting cables can wipe out all the losses and drawbacks associated with AC version : hysteresis loss, eddy current loss, dielectric loss of insulation and partial discharges. Therefore the results obtained in this study open an avenue to the DC high temperature superconducting cables which can possibly play dominating roles in the future underground power transmission.