Study on Ablation between Metal Sheath and Buffer Layer of High Voltage XLPE Insulated Power Cable

The corrugation aluminum (Al) is a common sheath structure of high voltage cross-linked polyethylene (XLPE) insulated cable in China due to its good bending performance. However, some problems, especially buffer layer ablation, have occurred frequently in cables due to such corrugated structure. At present, the causes of ablation are unclear, which makes it difficult to prevent relevant accidents. This paper aims at studying the possible causes of ablation by means of reproducing ablation in the laboratory. In the process of investigating ablation on failure cable, it is found that the Al sheath has some burnt stains, which is similar to discharge traces. From the discharge consideration, simulation method and actual experiments are carried out by a model sample built by an arc-shaped Al electrode system as well as a buffer layer to imitate the corrugated sheath structure in HV cable. The simulation result shows that when there is a bad contact between the Al sheath and buffer layer, the discharge will occur. Moreover, it is indicated by the experiment that the inception voltage of discharging will become higher with the increase of the electrode interval. Some further studies are carried out around the ablation morphology. The morphology of the ablated buffer layer from laboratory is observed by optical-microscopic, which shows great similarity with the ablation points in failure cables, verifying discharge is one of the causes of ablation.