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)在超导电力设备电气绝缘系统中的应用。在低温下，对液氮或液氦等流体的绝缘进行了大量的实用研究，但对用于高压设计的固体绝缘的研究很少。研究结果如下：(1)EPR绝缘在导体圆柱体相当粗糙的表面附近冷却到液氮温度时，没有发生机械故障。带填料的EPR在低温下长期运行时应具有较高的绝缘可靠性。(2)低温下的直流短路树起爆电压远高于常温下。这可能归因于电极的载流子注入损耗，并为超导电力装置的电绝缘设计提供了强有力的激励。(3)测量了有、无绝缘子的低温气体的直流击穿电压。击穿电压服从帕森定律，只随密度和厚度的乘积而变化。在低密度-厚度产品范围内，表面击穿很难在间隙击穿之前发生，这为聚合物材料(EPR)在超导电力设备电气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缘材料。

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.