Application of Electrical Insulating System of Superconducting Power Apparatus by Polymeric Composite Materials

研究人员一直在研究聚合物材料（乙丙橡胶（EPR））在超导电力设备电气绝缘系统中的应用。在低温下，对液氮、液氦等流体的绝缘研究较多，但对固体绝缘的研究较少，主要研究结果如下：（1）EPR绝缘在冷却至液氮温度时，导体圆柱表面粗糙度较大，不会发生机械失效。在低温下长期运行时，要求填充EPR具有高的绝缘可靠性。(2)低温下的直流短路树起始电压比室温下的高得多。这可能归因于电极的损耗载流子注入，并为超导电力设备的电绝缘设计提供了强有力的激励。(3)测量了有、无隔离层时低温气体的直流击穿电压。击穿电压服从帕邢定律，只随密度和厚度的乘积而变化。在低密度-厚度积范围内，在差距击穿发展之前，几乎不会发生表面击穿，这一研究结果为聚合物材料（EPR）在超导电力设备电绝缘系统中的应用开辟了一条途径。EPR是一种很有前途的低温固体绝热材料。

The investigators have been studying the application of polymeric materials (ethylene-propylene rubber (EPR)) to electrical insulation system of superconducting power apparatus. At cryogenic temperature, there are many practical insulation studies on fluids such as liquid nitrogen or liquid helium but scarce studies on the solid insulation enabling a high voltage design.The results are summarized as follows :(1) The EPR insulation did not suffer from the mechanical failure at the cooling down to liquid nitrogen temperature around the fairly rough surface of conductor cylinder. High insulation reliability of EPR with filler is expected during long term operation at cryogenic temperature.(2) DC short-circuit tree initiation voltage at cryogenic temperatures is much higher than that at room temperatures. This may be attributed to loss carrier injection from electrode and gives a strong incentive to design the electrical insulation of superconducting power apparatus.(3) The DC breakdown voltage of cryogenic gas with and without spacer has been measured. The breakdown voltage obeys Paschen's law and changes only with the product of density and thickness. In low density-thickness product range, surface breakdown can hardly occur before the gap breakdown develops.The results obtained in this study open an avenue to the application of polymeric materials (EPR) to electrical insulation system of superconducting power apparatus. EPR seem to be promising materials for solid insulation in the cryogenic region.