Revitalising high voltage cable: Exploring effective repair methods and influential factors for buffer layer defects using conductive silicone rubber

In recent years, the ablative discharge of the buffer layer in high-voltage (HV) cross-linked polyethylene (XLPE) cables has become a significant challenge for the operation and maintenance of power lines. However, there is a lack of effective methods to address buffer layer discharge defects. A practical approach is proposed to repair buffer layer defects and mitigate the associated discharge issues. To achieve this goal, the principles of repairing buffer layer defects are analysed by establishing an electrical network model that considers different contact states between the buffer layer and aluminium sheath. Based on this analysis, a method involving the injection of solidifiable rejuvenation fluid between the buffer layer and aluminium sheath is proposed to effectively suppress buffer layer discharge defects. Through simulation calculations, the minimum electrical conductivity and injection volume required to establish a reliable electrical connection between the buffer layer and aluminium sheath is determined. Additionally, a curable rejuvenation fluid containing conductive carbon black silicone rubber is prepared and analysed for its conductivity and flow properties at both the mesoscopic and macroscopic levels. Finally, a real cable office discharge test is conducted to compare the discharge behaviour of defective cables before and after repair. The results demonstrate that when the conductivity of the rejuvenation fluid exceeds 10⁻⁶ S/m, it effectively establishes a conductive channel between the insulation shield and aluminium sheath, thereby reducing the risk of discharge ablation. Furthermore, after injecting the rejuvenation fluid and completely covering the white mark defect, the discharge phenomenon in the buffer layer is significantly suppressed, leading to the restoration of its electrical performance.