Effect of Accelerated Laboratory Aging on Selected Electrical Properties of Medium-voltage Heat Shrink Cable Joints

Cross linked polyethylene (XLPE) cables are being used extensively in high-voltage power transmission and distribution networks around the world. However, such joints suffer high failure rates in extreme weather conditions. To investigate this issue, selected properties of 15-kV heat shrinkable XLPE cable joints produced by four manufacturers that are widely being used by electric power utilities in Saudi Arabia were evaluated before and after accelerated multi-factor aging. Aging stresses included high voltage, temperature cycling, and periodic applications of switching impulses while keeping joints in air as well as in water. Partial discharge characteristics, dissipation factor at 60 and 0.01Hz, and breakdown voltages were measured for un-aged and aged joint samples. The results show that partial discharge characteristics supplemented with a 0.01-Hz dissipation factor provide useful diagnostic information about the condition of such joints. Moreover, these properties also provide useful information about the comparative performance of joints produced by different manufacturers.