Influence of Dicumy1 Peroxide Content on DC Performance of Polyethylene for DC Cables

Peroxide crosslinked polyethylene (XLPE) has become the primary insulation material for extruded high voltage direct current (HVDC) power cables. Crosslinking process can influence the performance of XLPE cable insulation, especially the content of dicumyl peroxide (DCP) plays an important role on the DC properties of XLPE. This paper discusses DC performance of XLPE with a series of DCP contents, leading to different crosslinking degrees. The corresponding gel content and crystallization of XLPE with different crosslinking degrees were systematically investigated, and DC properties were characterized by space charge measurement, conductivity test and breakdown test. The results show that with the increase of gel content (0~90%), crystallinity of XLPE does not show much change with a reduction less than 5%, and the accumulated space charge changes from homocharges (negative) to heterocharges. Conductivity (~10–14S/m) of XLPE with different crosslinking degrees does not show significant differences. Moreover, DC breakdown strength of XLPE tends to increase with the increase of crosslinking degrees in the temperature range of 50°C~90°C. It thus suggests that the designing of crosslinking network of XLPE has great impact on the DC performance of cable insulation, and is vital in HVDC cable development.