Trap characteristics and space charge injection in XLPE cable insulation under repetitive damped AC voltage

Damped AC voltage (DAC) has been widely used for on-site partial discharge detection of XLPE power cables, whereas the effect of its DC charging stage on cable insulation remains unclear. In this work, XLPE specimens were subjected to repeated DAC voltage applications, and the resulting physicochemical properties, trap characteristics and space-charge behavior were investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermally stimulated depolarization current (TSDC), DC conductivity and pulsed electroacoustic (PEA) measurements. The results show that no obvious chemical change or crystallinity variation occurs after 500 DAC applications. However, at this stage, the trap density increases from 3.51×1015 m-3 to 1.06 × 1016 m-3 (by approximately three times), with space charge evolving from interfacial accumulation to full penetration across the sample, and the electric field distortion ratio rising from 19.3% to 47.6%. These findings suggest a possible transition from interface-dominated to synergistic interface–bulk charge interaction in XLPE under repetitive DAC stress, which may represent an important stage in the electrical aging process of this material.