机械拉伸对聚丙烯绝缘空间电荷与击穿特性的影响研究  

Effect of Mechanical Strains on Space Charge and Breakdown Characteristics of Polypropylene Insulation

作　　者：李忠磊 王赫宇 范铭升 周硕凡 杜伯学 LI Zhonglei;WANG Heyu;FAN Mingsheng;ZHOU Shuofan;DU Boxue(School of Electrical and Information Engineering,Tianjin University,Nankai District,Tianjin 300072,China;State Grid Jibei Electric Power Co.,Ltd.,Langfang Power Supply Company,Langfang 065099,Hebei Province,China;State Grid Jiangsu Electric Power Co.,Ltd.,Nanjing Power Supply Company,Nanjing 210019,Jiangsu Province,China)

机构地区：[1]天津大学电气自动化与信息工程学院,天津市南开区300072 [2]国网冀北电力有限公司廊坊供电公司,河北省廊坊市065099 [3]国网江苏省电力有限公司南京供电公司,江苏省南京市210019

出　　处：《中国电机工程学报》2022年第11期4255-4265,共11页Proceedings of the CSEE

基　　金：国家自然科学基金项目(52077148,U1966203)。

摘　　要：为研究机械拉伸对聚丙烯热塑性电缆绝缘空间电荷与击穿特性的影响,采用等温结晶方法制备具有不同结晶形貌的聚丙烯(polypropylene,PP)绝缘样品,研究不同拉伸率的PP绝缘样品直流电导、空间电荷与击穿特性,并对拉伸前后材料微观结晶形貌进行表征,分析机械拉伸下结晶形貌变化对电气性能的影响机理。结果表明:机械拉伸形变将导致PP绝缘电导率提高、空间电荷积聚量增多,以及直流击穿场强显著降低。相比于等规聚丙烯绝缘,等规聚丙烯/间规聚丙烯共混绝缘具有较高的断裂伸长率,在相同拉伸率情况下空间电荷密度较低,击穿场强提高。通过控制等温结晶时间可调控结晶度和结晶形貌,改善绝缘抗冲击性能,抑制拉伸条件下空间电荷注入,提升绝缘击穿场强。研究表明,机械拉伸应力导致球晶出现形变甚至破坏现象,晶区–非晶区界面形成缺陷,是导致绝缘空间电荷注入加剧、击穿性能显著下降的根本原因。This paper focused on the effect of mechanical strains on space charge and breakdown characteristics of polypropylene(PP)insulation for high-voltage cables.PP insulation samples were prepared by isothermal crystallization treatment whose DC conductivity,space charge,and breakdown characteristics were investigated under mechanical strains.The mechanism of mechanical strains on the electrical properties of PP insulation was analyzed by characterizing the microscopic crystalline morphology.The results show that mechanical strains of PP insulation lead to a higher conductivity,an increased space charge density,and a decrease of DC breakdown strength.The isotactic-PP(i PP)/syndiotactic-PP(s PP)mixture,with a higher elongation at break,is more outstanding on DC conductivity and breakdown strength than that of i PP insulation at the same strain rate.The isothermal crystallization treatment affects the crystallinity and crystalline morphology of PP insulation,which not only improves the impact resistance,but also elevates DC breakdown strength.In conclusion,the mechanical strains accelerate the injection of space charge and decrease breakdown strength,resulting from defects at the crystalamorphous interface,following with deformation and rupture of spherocrystals in PP insulation.

关 键 词：高压直流电缆 聚丙烯绝缘 机械拉伸 空间电荷 击穿强度 结晶形貌 

分 类 号：TM21[一般工业技术—材料科学与工程]