Study of amorphous phase evolutions of cable insulator during accelerated ageing program

The search for a better reliability of medium voltage cables is current. Accelerated ageing test, after a period of two years, allows one to determine the cable quality. Two cables performed with the same base resin from different manufacturing processes, one fulfilling the long duration test and the other failing it, have been analysed by thermally stimulated creep. This technique is sensitive to different amorphous domains allowing one to discriminate these cables before the test and to follow their evolution during ageing. This study shows that cables differ in the molecular mobility located at interphases between free amorphous domains and crystallites.