Investigation of electrical tree growth characteristics in XLPE nanocomposites

Failure of underground cables due to high degradation-rate phenomena, as partial discharges followed by electrical treeing, is one of the major causes of cable outages. Breakdowns occur mostly in correspondence of joints and terminations, where the electric stress can exceed the design electric field due to bad workmanship or manufacturing. Researches are being carried out to improve the resistance of insulation materials to such harmful electrical-aging phenomena. The use of nanocomposite cross linked polyethylene, XLPE, is investigated in this paper. Experiments of electrical tree growth on silica-nanostructured XLPE specimens, during which the time behaviour of partial discharges is recorded, are presented and discussed. Data are processed through clustering analysis, showing that addition of silica nano fillers with 3 and 5 %wt concentration improves noticeably PD endurance and breakdown time of XLPE material.