Comparative study on thermal-oxidative aging properties of XLPE insulation for 220 kV cable

With the imported material of the same voltage level as a reference, thermal-oxidative aging tests were done at different temperatures for domestically produced 220 kV crosslinked polyethylene (XLPE) AC cable insulating material. The aging behavior of the two materials was systematically characterized by investigation of infrared spectroscopy, differential scanning calorimetry, gel content, mechanical properties and electrical properties. The results show that the chemical composition, crystallization properties and crosslinking properties of the two materials are less affected by aging temperature, while the changes of mechanical and electrical performances are more obvious. As the aging temperature increases, the carbonyl index of imported material increases more obviously, and the gel contents of the two materials increase first and then decrease. The gel content of the imported material is relatively lower regardless of aging, and it is easier to crystallize. The mechanical property test results indicate that the thermal-oxidative aging performance of imported material is relatively better and it shows relatively higher tensile strength and elongation at break under various aging conditions before and after aging. The dielectric loss factors of the two materials increase after thermal-oxidative aging, but the difference between the two materials and the consequent temperature rise of the insulating layer are not significant. The domestic material has higher breakdown strength, higher electrical tree initiation voltage and slower tree growing rate. And regardless of the degree of aging, the domestic material obviously maintains its advantages in electrical strength. © 2024 Editorial Department of Electric Machines and Control. All rights reserved.