Microphysical characterization of XLPE cable insulation after electrical aging

Many different approaches to explaining the long-term degradation of polymeric insulating materials have been suggested, including chemical, electrical and mechanical processes. However, radial and angular variations observed in several physical properties of the polymeric insulation of cables often result from manufacturing processes, not from aging conditions. This paper reports many microphysical measurements on laboratory-aged and unaged cable samples: infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), density and dielectric relaxation spectroscopy. Variations in these characteristics have been recorded as a function of both radial and angular coordinates for XLPE power cable samples and, in most cases are found to be strongly correlated to optical birefringence measurements made on the same samples. However, in the case of dielectric relaxation measurements (time-domain-spectroscopy), the samples were not characterized by their birefringence values