Abstract
Transmission power cables are heated by the conductor current. Morphology of the XLPE insulation may be changed through the thermal aging. Disk shaped insulating materials with semiconductive electrodes were used in order to understand this thermal effect against the dielectric breakdown strengths. The disk specimens were aged at 80°C and 100°C before the breakdown strength measurements.
These results showed that their dielectric breakdown strengths were improved with aging time. Analytical investigation of the insulating materials indicated that there were morphological changes such as increases of the lamella thickness and the spherulite diameter and decrease of the averaged lamella angle through heating. Cable specimens aged thermally with the same condition as the disk specimens were also observed the similar morphological changes in the insulation. Therefore the promotion of the crystallization by thermal aging is concluded to be effective in improving the breakdown strength of the XLPE insulation, unless it causes extreme deterioration.
