液氮环境中3种聚合物薄膜老化和拉伸状态下的绝缘强度

Dielectric Strengths of Three Polymer Films Under Aging and Tension Status in Liquid Nitrogen Environment

用于超导设备的薄膜型绝缘材料绕包于导体时往往承受一定的绕包张力,且由于工作环境温度的变化、机械应力等作用会发生老化。为研究薄膜型绝缘材料在液氮环境中老化拉伸状态下的绝缘强度,设计了一套测试电极系统对聚酰亚胺(Kapton)、聚丙烯层压纸(PPLP)和聚四氟乙烯(PTFE)3种薄膜在液氮中经过不同老化处理后拉伸状态下的工频和直流绝缘强度进行了实验研究,结果发现老化拉伸状态下交、直流击穿电场强度大多在较小幅度内发生变化,而经过冷热循环处理后的聚丙烯层压纸交流、直流击穿电场强度均发生了跳跃性地下降,因而在选择聚丙烯层压纸作为超导电力设备的绕包型绝缘材料时,应充分考虑工作温度剧烈变换导致的材料老化因素的影响。3种材料的直流击穿电场强度要普遍高于交流击穿电场强度。

Insulation films used for superconducting devices usually endure certain lapping tension when they are lapped on the conductor,and the aging of the film will occur due to the mechanical stress and the temperature variation of operating environment.To research the insulation strength of the insulation film under aging and tension status in liquid nitrogen environment,a test electrode system is designed to experimentally research AC and DC breakdown field strengths of three kinds of insulation films made of kapton,polypropylene laminated paper（PPLP） and polytetrafluoroethylene（PTFE） respectively.Experiment results show that AC and DC breakdown field strengths of the three kinds of insulation films mostly vary within a smaller range,however both AC and DC electrical breakdown strengths of PPLP film after the heat-cold circulation treatment decrease obviously under the experimental condition,therefore when PPLP is chosen as the lapped insulation material for superconducting power equipments the impact of material aging factors due to drastic variation of operating temperature should be fully taken into account.Besides,it is shown from experimental results that the DC breakdown field strengths of the three insulation films are higher than their AC electrical breakdown strengths in general.