尖端及气隙联合缺陷下XLPE材料电树枝起始特性及其影响因素研究

Study on electrical treeing characteristics of XLPE materials with joint defects of tip and air gap and its influencing factors

交联聚乙烯(XLPE)中内部缺陷是导致电缆中电树枝产生的主要诱因,而电树枝的出现将造成电缆绝缘的整体失效,探寻不同绝缘缺陷特征对电树枝起始的影响规律及机理,可为设计、生产环节中改善电缆绝缘提供理论依据。考虑到凸起及气隙的联合缺陷为电树枝引发的主要诱因,本文搭建了针-电极短电缆实验平台以模拟缺陷下电树枝的引发及生长,并建立了缺陷下电应力物理模型,明确了缺陷模型下各缺陷特征对电树枝起始发展的影响规律。研究表明:XLPE电缆中半导体层缺陷的最大电场分布可采用针-板电极下最大场强Mason模型进行描述;由实验及数值化模型结果分析出缺陷的突刺曲率、微孔压强及材料耐受阈值ΔW_(0)与电树枝起始电压呈正相关,可分别从制造工艺、安装铺设等过程中调控三类缺陷特征,以提高实际工程中XLPE电缆的抗电树枝老化能力。

Defects in XLPE(Cross-linked polyethylene)cable insulation are the main cause of forming of electric branch.Exploring the influence law and mechanism of different insulation defect parameters on the initial voltage of electric branch can provide theoretical basis for improving cable insulation in production and installation.The needle-electrode short cable test system is used to simulate the influence of the size of the external semiconductor layer spike on the start of the electric branch,and the physical model of the defect is constructed to analyze further the influence law of each defect parameter.The research shows that the maximum electric field distribution can be studied by the maximum field strength Mason model of the pin-plate electrode.According to the simulation test and the numerical model results,there is a positive correlation between the spur curvature,the micro-pore pressure,the energy generated by the electric branch and the initial voltage of the electric branch.The ability of the cable insulation to resist electric tree aging can be improved by modifying the three types of defect character in the process of practical manufacturing and installation.