Insight on micro-structures of rejuvenated water-tree cables by two kinds of injection liquids

To understand the relationship between the electrical properties and micro-structures for rejuvenated watertree cables, the changes of electrical properties and micro structures were compared for the water-tree samples injected by two kinds of rejuvenation liquids. A water tree accelerated aging system was employed to obtain water trees in cross-linked polyethylene (XLPE) cable samples, and the samples were subjected to injection with two kinds of rejuvenation liquids. AC breakdown tests show that both the two groups of samples have significant increase in breakdown voltage, one group has a greater increase than another. By scanning electron microscope (SEM) analysis, nano-scale fillers are observed inside the breakdown channels of the rejuvenated samples, the distribution of the fillers in XLPE matrix are different for the two groups of samples. The more scattered nano-particles embed in the XLPE matrix, the more electrical properties will be increased. According to the experimental results, a coupling model of the fillers inside water tree area was presented.