XLPE电缆绝缘片晶周期性结构演变及其对电性能的影响  

Lamellar Periodic Structure Evolution of XLPE Cable Insulation and Its Influence on Electrical Properties

作　　者：周士贻 门业堃 刘博 及洪泉 陈道远 高建 李建英[2] ZHOU Shiyi;MEN Yekun;LIU Bo;JI Hongquan;CHEN Daoyuan;GAO Jian;LI Jianying(State Grid Beijing Electric Power Research Institute,Fengtai District,Beijing 100075,China;Xi’an Jiaotong University,Xi’an 710049,Shaanxi Province,China)

机构地区：[1]国网北京市电力公司电力科学研究院,北京市丰台区100075 [2]西安交通大学,陕西省西安市710049

出　　处：《中国电机工程学报》2024年第3期1205-1213,I0030,共10页Proceedings of the CSEE

基　　金：国家电网有限公司科技项目资助(5108-202218280A-2-353-XG)。

摘　　要：为了研究长期高温条件下高压直流电缆交联聚乙烯(cross-linked polyethylene,XLPE)绝缘片晶周期性结构演变对直流绝缘特性的影响,将500 kV直流XLPE电缆绝缘层的薄片试样置于135℃条件下加速热老化。采用小角X射线散射(small angle X-ray scattering,SAXS)和差示扫描量热法(differential scanning calorimetry,DSC)分析热老化对组成球晶的片晶/无定形区过渡界面、片晶和片晶长周期结构的影响。同时,分析XLPE直流电导特性和击穿强度的变化。实验结果表明:片晶/无定形区界面厚度、片晶厚度、片晶长周期尺寸随着老化的进行先略微增大后逐渐减小,在老化336 h时出现最大值,这与电荷注入阈值场强和直流击穿强度具有相似的变化规律,而与载流子迁移率变化和片晶间无定形区尺寸的变化相反。基于陷阱控制的阈值场强变化和自由体积击穿理论,分析片晶周期性结构变化对直流击穿强度的影响。综合分析可知,经过短时间热老化有助于改善XLPE的片晶周期性结构,从而提升直流击穿强度。In order to study the effect of evolutions in the lamellar periodic structure of cross-linked polyethylene(XLPE)insulation for high-voltage DC cables on the DC dielectric properties under thermal aging,the thin slice samples of XLPE insulation layer of 500 kV DC cable are subjected to accelerated thermal aging at 135℃.The size of the lamellae/amorphous interphase,lamellae,and the long period of lamellae are analyzed by using small angle X-ray scattering(SAXS).The changes of DC conductance and breakdown characteristics under thermal aging are also analyzed.The experimental results show that the interphase thickness of lamellae/amorphous area,lamellar thickness and lamellar long period size increase slightly first and then gradually decrease with aging time,and the maximum value occurs when aging for 336 h,which has a similar change rule to the threshold field strength and DC breakdown strength.But it is opposite to the variation of the carrier mobility and the variation of the amorphous region size between lamellae.The effects of periodic structure of lamellae changes on DC breakdown strength are analyzed based on trap-controlled threshold field strength and free volume breakdown model.Comprehensive analysis shows that short-term thermal aging helps to improve the microcrystalline structure of XLPE,thereby improving the DC breakdown strength.

关 键 词：交联聚乙烯 过渡界面 片晶长周期 阈值场强 直流击穿 

分 类 号：TM75[电气工程—电力系统及自动化]