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

调查人员一直在开发挤出乙丙橡胶(EPR)绝缘超导电力电缆。本研究研制的模型电缆结构非常简单：银套铋系高温超导导线并联在稳定芯黄铜管上，用聚乙丙橡胶和半导体屏蔽层进行电绝缘。通过对芯管上超导导线布置的优化，在室温(RT)和液氮温度(77K)之间反复热循环后，超导导线与EPR绝缘材料具有良好的接触。这表明，EPR在冷却时的径向、周向和长度方向的热收缩不影响超导导线的电流特性。因此，EPR绝缘适用于一般认为易受机械应力影响的高温超导体。直流临界电流和失超电流的测量也表明，它们只受到包裹的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超导电缆相关的所有损耗和缺点：滞后损耗、涡流损耗、绝缘介质损耗和局部放电。因此，本文的研究成果为未来地下输电中可能发挥主导作用的直流高温超导电缆开辟了一条新的途径。

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.