在XLPE电缆加速老化过程中理解水树的自愈性

发布时间：2018-10-29 12:43

【摘要】：针对加速XLPE电缆绝缘水树老化过程中发现的绝缘自愈现象,对水树生长和绝缘自愈性机理进行了分析讨论。利用水针电极法对XLPE电缆绝缘进行加速水树老化,样本介质损耗因数随老化时间推移而增大,但一旦停止施加电压,介质损耗又会逐渐恢复到较低水平,出现了自愈现象。通过建立由一系列充水微孔和微观通道连接而成的水树模型,进行电场有限元计算,发现当水树通道打开时水树尖端电场畸变严重,由此产生的扩张能量使绝缘疲劳断裂,水树生长,介质损耗增加;停止施加电压后,水树通道内出现弹性恢复使水分被挤出,通道逐渐关闭,水树区变成孤立的充水微孔,绝缘自愈。再次施加电压后,充水微孔端部和关闭的水树通道内电场显著提升,水树通道逐步打开。研究表明,水树的自愈和水树通道的打开是一个逐步的过程,需要一定的时间,主要决定于施加的电场大小和绝缘的屈服强度。
[Abstract]:In this paper, the mechanism of water tree growth and insulation self-healing is analyzed and discussed in view of the phenomenon of insulation self-healing found in the process of accelerating XLPE cable insulation water tree aging. The water needle electrode method is used to accelerate the water tree aging of XLPE cable insulation. The sample dielectric loss factor increases with the aging time, but once the applied voltage stops, the dielectric loss will gradually recover to a lower level, and the phenomenon of self-healing appears. By establishing a water tree model which is connected by a series of water filled micropores and micro channels, the finite element calculation of electric field is carried out. It is found that the electric field distortion at the water tree tip is serious when the water tree passage is opened, and the resulting expansion energy makes the insulation fatigue fracture. Water tree growth, medium loss increased; When the applied voltage is stopped, elastic recovery occurs in the water tree channel and the water content is squeezed out, the channel is gradually closed, and the water tree area becomes an isolated water filling micropore, and the insulation heals itself. When the voltage is applied again, the electric field in the end of the water filling microhole and the closed water tree channel is increased significantly, and the water tree channel is gradually opened. The results show that the self-healing of the water tree and the opening of the channel of the water tree are a gradual process, and it takes a certain time to determine the magnitude of the applied electric field and the yield strength of the insulation.
【作者单位】：四川大学电气信息学院;四川电力科学研究院;
【基金】：四川省电力公司科技项目基金资助项目(2010035)
【分类号】：TM247

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