Electrical breakdown characteristics of the XLPE cables under AC, DC, and pulsating voltages

Electrical breakdown strength of the 5 kV XLPE cables was studied under ac, de, and pulsating voltages. The pulsating voltage was obtained by superimposing ac voltage on de voltage. In the later case, the ratio of ac to de voltage components (p = Vac/Vdc) was varied between the limits of 0.1<p<10. Both the sound and imperfect cables are used as the test samples. Two types of imperfections are studied. Cables samples with artificial holes and cables samples with embedded needles. Study results shows that the pulsating voltage is an effective way to detect the imperfections inside the XLPE cables.