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

研究人员一直在研究高分子材料（乙丙橡胶）在超导电力设备电绝缘系统中的应用。在低温下，对液氮或液氦等流体的实用绝缘研究很多，但对高压设计的固体绝缘研究很少。结果表明：(1)在导体圆柱体表面相当粗糙的情况下，EPR绝缘在冷却至液氮温度时没有发生机械失效。在低温下长期运行时，填料EPR具有较高的绝缘可靠性。(2)低温下直流短路树起始电压远高于常温。这可能是由于电极的损耗载流子注入，这对超导电力设备的电绝缘设计具有强烈的激励作用。(3)测定了低温气体有无间隔的直流击穿电压。击穿电压服从Paschen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，在间隙击穿发生之前，表面击穿几乎不可能发生。本研究结果为高分子材料在超导电力设备电绝缘系统中的应用开辟了一条新途径。EPR是一种极有前途的低温地区固体绝缘材料。

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.