XLPE 电缆水树老化过程中半导电层缺陷的形成机理

Mechanism of Defects Formation in Semicon Layers of Water-tree Aged XLPE Cables

交联聚乙烯(XLPE)电缆的半导电层缺陷诱发机理尚无定论。为此,在加速水树老化实验的基础上,观测了水树老化后电缆的内、外半导电层中的缺陷,并对这些缺陷的形成原因进行了讨论。采用水针法对长度为70 m的XLPE电缆进行加速老化,电缆的绝缘性能逐渐下降,并在绝缘层中观察到水树缺陷。通过扫描电镜(SEM)观测到,老化样本的半导电层中有大量孔洞缺陷。进一步采用X射线能量色散谱(EDS)对内、外半导电层中的化学元素进行定量分析证明,老化后半导电层中氧(O)元素含量显著减少。因此,在长期老化过程中,半导电层中可能发生了电解质水溶液的电解反应,并生成了氧气(O2)和臭氧(O3),这种气体的生成是半导电层中孔洞缺陷发生及发展的原因。

There is no widely accepted theory of defects formation mechanism in semiconductive layers of XLPE cables. Therefore, on the basis of accelerated aging tests, we observed the defects in both inner and outer layers of water-tree aged XLPE cables, and then discussed the mechanism of these defects＇ formation. A 70-meters-long XLPE cable was arti- ficially aged using the water-needle method to weaken the insulation performance of aged cable, and water-tree defects were observed in the cable＇s insulation. Observation with scanning electron microscope indicates that there are voids and porous defects inside the semicon layer of the aged sample. The energy diffraction spectrum analysis proves that the oxy gen in the semicon layers of the aged sample is reduced significantly. It is concluded that there is electrolysis reaction of electrolyte solutions in the cable＇s aging process. The reaction generates oxygen gases （02 and 03）; the gas pressure and the strong oxidation of this oxygen gas cause the voids and porous defects inside the semicon layers.