Experimental Study on Rejuvenation of Aged Power Cables via Simulation Operation

Thermal effects play a crucial role in the evolution of insulation performance in power cables during long-term operation. Before the experiments, crosslinked polyethylene (XLPE) sheets and cables were thermally aged at 105 °C for up to 180 days. Then, the heat treatments on XLPE sheets and cables were conducted in three stages. Firstly, the aged sheets were subjected to heat treatment with a temperature range of 90 to 115 °C at intervals of 5 °C, with each step lasting for 20 h. Secondly, a 7-year-serviced cable underwent simulated cable operation at the same temperature as the XLPE sheets. Thirdly, two 15- and 30-year-serviced cables were treated at temperatures ranging from 90 to 105 °C, adhering to the same intervals as the second stage. The differential scanning calorimetry (DSC), cross-linking degree, DC conduction, and breakdown strength were measured. The results show that both heat treatment methods are effective in enhancing crystallization characteristics and conductivity for XLPE sheets and aged cables, and the optimum values were achieved at decreasing temperatures as the aging period extended. Moreover, the heat treatment on retired cables yielded similar results, suggesting that a heat treatment resembling cable operation at higher temperatures would initially be beneficial for cable rejuvenation.