低温环境下XLPE材料中水树生长特性的研究

Research on Characteristics of Water Tree Growth in XLPE under Low Temperature Environment

为了研究低温条件下水树的生长特性,研究了XLPE薄片样本在0℃下不同老化时期的水树生长速率变化。在XLPE薄片样本中制造针孔缺陷,之后将样本分为3组,并对其在0℃下分别进行为期14 d、21 d、28 d的加速水树老化。利用光学显微镜观测样本中的水树微观形貌和水树长度,并结合电场仿真分析水树在低温下生长速率变化原因。实验结果表明,在低温条件下,样本中的水树明显呈枝状。此外,水树生长速率随着老化时间的增加逐渐增加。电场仿真结果表明,水树长度越长,水树尖端的电场越强。根据水树生长的电机械老化理论,电场越大,水树尖端处的XLPE分子链受到的麦克斯韦应力越大,分子链越容易发生疲劳断裂,导致水树生长速率越大。

In order to investigate the characteristics of water treegrowth under low temperature,the propagation rates of water trees in XLPE sheet samples are researched in different aging periods.Pinhole defects are made in XLPE sheet samples,then the samples are divided into three groups,and they are subjected to an accelerated water tree aging for 14,21 and 28 days,respectively.The morphology of water trees is observed by an optical microscope,and the length of water trees are measured.Combining with the electric field simulation,the reasons for the changes of the propagation rates of water trees under low temperature are analyzed.The results show that the growth rate of water trees increases with time under low temperature.The experimental results show that under low temperature,the water trees are in dendritic shape.In addition,with the increase in aging time,the propagation rate of water trees increases.The electric field simulation shows that the electric field strength at the water tree tips becomes greater with the increase in water tree length.According to the electrical mechanical damage theory of water trees,the stronger the field strength,the greater the Maxwell forces at the water tree tips,and the molecular chains of XLPE can fracture easier under the effect of the Maxwell forces.As a result,the propagation rate of water trees can become larger.