Influence of defects on insulating properties of XLPE cable

The influence of defects on the insulating properties of XLPE (cross-linked polyethylene) cables was studied using XLPE cables containing artificial defects. It was confirmed that the AC breakdown strength of the cables decreases with the increase of void size, while the existence of voids does not have any effect on impulse breakdown strength. The contaminants and the protrusions decrease both AC and impulse breakdown strengths. The value of the life exponent, n, of the V-t characteristics of the XLPE cable containing voids was estimated to be smaller than that of the cables containing contaminants or protrusions. In addition to to the influence of those defects on initial and long-term performance of the cables, the influence of impulse voltage on the long-term performance of the cable, together with the behavior of the space charge accumulated around the defects, was investigated. It was found that impulse voltage greatly affects the long-term performance of cables containing voids