交联聚乙烯中水树枝向电树枝的转化

Transformation of Electrical Tree from Water Tree Degradation in XLPE

水树枝老化是运行在潮湿环境下的聚烯烃电力电缆发生绝缘击穿的主要诱因,水树枝在一定情况下可能引发电树枝,进而导致绝缘击穿。该文主要研究水分和水树枝劣化对交联聚乙烯(cross-linked Polyethylene,XLPE)中电树枝引发生长的影响。选用过氧化物交联聚乙烯作为实验材料,用水针电极、高频加速老化的方法培养水树枝,采用计算机实时显微数字摄像系统观测电树枝的引发和发展。分别研究了湿润水树枝和干燥水树枝在不同电极类型(水针电极、钢针电极)、不同电压下(15、20 kV)向电树枝的转化规律。实验研究发现:就电树枝的平均引发时间而言,未劣化试样最短,湿润水树枝试样最长,干燥水树枝试样介于二者之间;就电树枝引发率而言,干燥水树枝试样最高,湿润水树枝试样最低,未劣化试样介于二者之间;采用水针电极时,3种试样引发的电树枝均为枝状。结合对比3种试样中电树枝的形态,研究了湿润水树枝和干燥水树枝中电树枝的引发和生长机制。

Water treeing is the main inducement of insulating breakdown of long-time operation polyethylene（PE） power cables in humid environment.Water tree propagates to some extent may initiate electrical tree,which can eventually lead to insulation breakdown of power cables.The influence of moisture and water tree degradation on the initiation and propagation of electrical trees in cross linked polyethylene（XLPE） was studied.During the experiments,peroxide crosslinked polyethylene was chosen as the experimental material,liquid needle electrode and high frequency accelerated aging method were used for water tree development,and real-time digital microscopic camera system was used for observation of water-tree-transformed electrical treeing.The transformation of electrical trees from wetting and drying water tree samples with different electrodes（water needle electrode,steel needle electrode） was studied at different voltages（15kV,20kV）.Three experimental results are obtained.The average electrical tree initiation time of non-deterioration samples is shortest,that of wetting water tree samples is longest,while that of drying water tree samples is the medium of the two mentioned above.The electrical tree initiation rate of drying water tree samples is highest,that of wetting water tree samples is lowest,and that of non-deterioration samples is the medium of the two mentioned above.When water needle electrode is used in the three kinds of samples,the electrical trees initiated are all branch-like.The different mechanisms of electrical treeing in the three kinds of samples are studied.