A new rejuvenation method based on nano-filler for water tree aged cables

In this paper, a new rejuvenation method toward forming inorganic nano-particles inside water tree voids was presented. A water-needle method was employed to obtain water tree aged cables, and the samples were subjected to inject with two groups of rejuvenation liquids. The results of dielectric loss factor (tan6) and AC breakdown tests show that both two groups of samples have significant increase in insulation performance, and the reformulation leads a greater increase in cables insulation performance than the previous formulation. The result of a microscope observation shows that there are polymers filling the voids of water tree after the rejuvenation. By a scanning electron microscope (SEM) analysis, nano-fillers were observed inside the AC breakdown channels of the rejuvenated samples and the dispersability of 11:1110 composite fillers in XLPE matrix are different for two groups. According to the results, it shows that the new rejuvenation method can rejuvenate the water tree in XLPE cables, effectively enhancing the insulation level of the aged cables. Moreover, the dispersability of nano composite fillers in XLPE matrix plays important role on the rejuvenation effect.