Development of Extruded Polymer Insulated DC Superconducting 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。这项研究的目的有两个方面。一是在相关电缆设计中评估导体的性能。二是评价EPR绝缘设计在高温超导导线粗糙表面上的性能。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。对包覆EPR绝缘层前后超导体的交流损耗进行了测量，其大小与包覆EPR绝缘层前后无显著差异。这表明EPR在冷却时径向、周向和纵向的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是易受机械应力的。临界电流和猝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。此外，EPR样品的直流短路树形试验清楚地显示出极高的树形电阻，这对直流设计非常有利。这些结果表明，在高温下，挤压聚合物绝缘克服了直流电缆的障碍，实现了高温超导直流电缆的设计。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。少

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 layrs. The purposes of this study are two fold. One is to evaluate the conductors behavior in the relevant cable design. The other is to evaluate the performance of the EPR insulation design on the rough surface of high temperature superconducting wires. 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). The ac loss of superconductors was measured before and after the wrapping of EPR insulation layr and there were no difference i … More n its magnitude. This reveals that the radial, circumferential and lengthwise 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 which are generally considered to be vulnerable to the mechanical stress. The dccritical current and quench current measurements also showed that they are only slightly affected by the mechanical stresses of the wrapped EPR insulation. The furthermore the DC short circuit treeing test of EPR sample clearly gave extremely high tree resistance which is very favorable results for designing DC.These results are indicating the surmounting of obstacles set against the DC cable by extruded polymer insulation at RT and the realization of high temperature superconducting DC cable design by extruded 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. Less