Effects of Residual Space Charge on Breakdown Voltage in Silicone Rubber Materials Used in HVDC Cables

The insulation system of high-voltage direct current (HVDC) cable joints is one of the most vulnerable components, with the enhanced insulation section being particularly prone to breakdown faults upon re-energization after power outages. This phenomenon is closely associated with residual space charges after depolarization, yet its specific influencing mechanism remains unclear. This work integrates pulsed electroacoustic (PEA) measurements with pre-voltagedepolarization DC breakdown testing to elucidate the space charge-breakdown strength correlation in three silicone rubber variants (SR-X, SR-1, SR-2). Experimental results demonstrate that SR-1 and SR-2 exhibit a typical polarity effect after prevoltage application, leading to an increase in breakdown strength. Conversely, SR-X exhibits pronounced residual space charge accumulation-resulting in substantial field distortion and a 16.93% maximal degradation of dielectric breakdown strength.This discrepancy reveals the dual role of residual space charges in influencing the dielectric breakdown strength.