Application of Polymeric Super Electrical Insulating Materials to Superconducting Power Apparatus

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。超导电力装置是未来高效处理大功率电力的有效途径。为了评估超导装置的长期可靠性，有必要研究低温下的电绝缘性能。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）研究了低温下EPR绝缘的树枝化现象。进行了直流短路树枝化试验。低温下的直流短路树启动电压远高于室温下的直流短路树启动电压。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。(2)在低温条件下，测定了交联剂、填料等添加剂对EPR材料的介电损耗、介电损耗因子的影响。结果表明，即使在低温区，添加剂也能提高EPR薄膜的tan δ。(3)为了设计超导电力设备的电绝缘，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. The superconducting power apparatus is the promising ways for handling huge electric power efficiently in the future. It is necessary to study the behavior of electrical insulation at cryogenic temperature to evaluate long term reliability as a superconducting 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 treeing phenomena of EPR insulation at cryogenic temperature have been studied. DC short-circuit treeing tests are performs. DC short-circuit tree initiation voltage at cryogenic temperatures in 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.(2) The effect of additives such as crosslinking agent and fillers on tandelta, dielectric dissipation factor of EPR have been measured at cryogenic temperature. The results show that additives increase tandelta of relatively thin films of EPR even in cryogenic temperature region.(3) To design the electrical insulation for a superconducting power apparatus the DC.breakdown voltage of cryogenic gas with and without spacer have been measured. The breakdown voltageobeys Paschen''s law and change 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.