交联聚乙烯中水树在温度循环条件下的生长特性

Growth Characteristics of Water Trees in XLPE Under Temperature Cycling Conditions

为理解温度循环条件下交联聚乙烯(cross-linked polyethylene,XLPE)电缆中水树的生长特性,研究了不同温度变化条件下水树的生长行为,发现温度循环条件下的水树生长会出现减速–加速的循环过程,并对温度循环条件下的水树生长机制提出了一种新的可能解释。首先使用XLPE样本分别进行0℃恒温、0℃和60℃温度循环、60℃恒温的加速水树老化实验,通过显微镜观测水树主体形态和尺寸、扫描电镜观测0℃恒温和60℃恒温下水树的微观结构,并在COMSOL软件中对不同温度条件下水树的生长模型分阶段进行仿真分析。结果表明:0℃和60℃温度循环条件下的水树生长分为2个阶段:第1阶段是0℃→60℃(低温转高温)下水树的减速生长,第2阶段是60℃→0℃(高温转低温)下水树的加速生长。这可能是由于温度变化导致水树微观结构产生差异,造成不同电场力下的XLPE分子链局部取向程度不一致所致。

In order to understand the growth characteristics of water trees in cross-linked polyethylene(XLPE) cables under temperature cycling conditions, the growth behavior of water trees under different temperature changes was studied. It is found that the growth of water trees under temperature cycling conditions will have a deceleration-acceleration cycle. Furthermore, a new possible explanation for the mechanism of water tree growth under temperature cycling conditions was proposed. Firstly, XLPE samples were used to carry out accelerated water tree aging experiments at a constant-temperature of 0 ℃, 0 ℃ and 60 ℃ temperature cycle, and a constant-temperature of 60 ℃. The main shape and size of the water tree were observed by microscope, and scanning electron microscope was used to observe the microstructure of water tree area at 0 ℃ and 60 ℃ temperatures.Moreover, the growth model of the water tree under different temperature conditions was simulated by stages in COMSOL software. The water tree growth under 0 ℃ and 60 ℃ temperature cycling conditions is divided into two stages: the first stage is the deceleration growth of water trees from 0 ℃ to 60 ℃(low temperature to high temperature), and the second stage is the acceleration growth of water trees from 60 ℃ to 0 ℃(high temperature to low temperature). The reason may be that the temperature changes lead to differences in the microstructure of the water tree, resulting in inconsistent local orientation of the XLPE molecular chains under different electric field forces.