Research on Composition of White Powders in High-voltage XLPE Cable with Buffer Layer Failure

Abstract

Recently, a new type of high-voltage cross-linked polyethylene (XLPE) cable failure called buffer layer failure occurs from time to time. The failure occurs at the cable body between the insulation screen and the aluminum sheath, which is different from the traditional one that occurs at the intermediate joint or cable accessory. The main feature is white corrosion marks on the inner surface of the aluminum sheath, dotted potholes, and ablation marks on the outer surface of the insulation screen. Especially there are dotted white powder and burnt holes on the surface of the water-blocking tape. Given the white powder in this new failure, imitating the actual structure of the cable, this paper builds a three-layer model of the buffer layer in the laboratory. The water-blocking tape is placed between the insulation screen and the aluminum sheath. The white powders were reproduced by injecting water into the tape and extruding it. The micro-morphology of white powder was observed by scanning electron microscope (SEM) and the element composition was measured by energy dispersive spectrometer (EDS). The results show that the white powder of water-blocking tape contains Al, which is the product of a chemical reaction with an aluminum sheath.