Deterioration analysis of ex-serviced 110 kV XLPE cable based on residual charge method

In this paper, the deterioration investigation was carried on an ex-serviced 110 kV cross-linked polyethylene (XLPE) cable. XLPE sheets sliced from the cable insulation were taken as the test samples and the residual charge method was used as the diagnostic method. Two aluminum foils attached on the both sides of sample surface made the electrode constitution, between which the voltage was applied and the current was simultaneously measured. The residual charge was calculated to estimate the degree of the degradation. Additionally, Tan¿ test was carried out to assist the evaluation of cable degradation. Obtained results show that the degradation degree within the insulation varies with the changes of the position. The XLPE sheets near the outer semicon and the conductor aged more severely than that of the middle part. Meanwhile, the cable was anatomized and it was found that the water blocking layer had mildewed and the color of the outer part insulation turned into black.