The Effect of Superimposed Switching Impulses on Space Charge Accumulation in XLPE-insulated HVDC Cables

Electrical apparatus including HVDC cables are subject to transient events during their operating lifetime. This paper studies the effect of Superimposed Switching Impulses (SSIs) on the space charge accumulation behavior in extruded HVDC cable insulation. Results show a significant increase in the ability of the aged XLPE to store space charge at room temperature. This tendency is further enhanced at higher temperatures (i.e., 70°C). The apparent trap depth characterizing this material is increased by aging process. Local field enhancement points were detected due to positive hetero-charge accumulation especially at high temperatures.