The evaluation of the buffer layer chemical corrosion for HV XLPE insulated cable with corrugated aluminium sheath structure

Aluminium (Al) corrugation is one of the mainstream sheath structures in high voltage cross-linked polyethylene (XLPE) insulated cable in China, owing to its advantage of good bending performance. Recently, the reliability of the cable with such a corrugated Al sheath has been suspected, since the buffer layer ablation was found many times in the failure cables with such a sheath structure. This study attempts to investigate the underlying mechanism of such a buffer layer chemical corrosion phenomenon through reproducing the ablation in laboratory. For indication upon the relationship between ablation and corrosion, a corrosion device with sheath-buffer-layer model sample is designed and the similarity of the ablated samples from laboratory and failure cables is analysed by Optical-Microscopic (OM) and Scanning Electron Microscope (SEM), revealing corrosion is one of the causes of ablation. After reaction, the gas is pumped into Gas Chromatography (GC) Analyser and the reaction product is detected by X-ray Photoelectron Spectroscopy (XPS). The test results show that the H2 content in the gas after reaction is obviously higher than that in air and the composition of ablation product from laboratory and failure cables is similar, which provide proofs for chemical reaction.