DC electrical conductivity of XLPE cable models aged under multiple thermal-electrical stresses

The DC electrical properties (conductivity, charging, and discharging currents) of XLPE (cross-linked polyethylene) cable models aged under multiple thermal-electrical stresses for different aging times are investigated over the temperature range 55 to 90°C. The conductivity of the cables aged under thermoelectrical stresses exhibits a nonmonotonic behavior with aging time, similar to that of other investigated properties, such as density, crystallinity, and electric strength; however, its variations are much greater, indicating a higher sensitivity to degradation phenomena due to aging. This could provide an effective diagnostic tool for monitoring cable behavior in service. A relaxation process, which may be ascribed to an interfacial polarization of the Maxwell-Wagner-Sillars type, is observed at the intermediate aging times, for which conductivity exhibits its maximum value. In the range of temperature and electric field studied, ionic charge carriers seem to make the most contribution to both the conduction and relaxation processes