Study of cross-linked polyethylene under high field

The authors describe some initial work on the laboratory aging of XLPE (cross-linked polyethylene) cables under high electrical stress (30 kV/mm) with or without thermal cycling during four months. After aging, the XLPE insulation was characterized by electrochemistry, differential scanning calorimetry, and Fourier transform infrared spectroscopy. It was observed that a large quantity of water (from 50 to 100 ppm) was often correlated with water trees in aged cables. When the water quantity was lower, water trees were found only after a mechanical stress of the lead cover. Decreases of crystallinity percentage and fusion temperature were also observed.<>