Effect of partial discharge aging on charge transport of oil-impregnated paper for cables

Partial discharge (PD) within cavities in oil-impregnated paper (OIP) is one of the key aging mechanisms that can alter space-charge behavior and eventually contribute to insulation failure in underground cables. This study investigates the evolution of charge-transport characteristics in a three-layer OIP sample containing an artificial cavity under PD aging. Time-resolved pulsed electroacoustic (PEA) measurements show that PD aging changes the measured space-charge profiles, leading to a lower injected charge density, faster charge redistribution during depolarization, and enhanced charge accumulation near the oil–paper interfaces. To interpret these experimentally observed trends, a modified charge transport model incorporating dual-trap energy levels and hopping conduction is developed. Model fitting to the measured PEA profiles suggests that PD aging is associated with a reduction in the effective deep-trap energy level and an increase in shallow-trap density, which facilitates carrier de-trapping and promotes the redistribution of space charge from the bulk region toward the interfaces. The results provide insight into the relationship between PD-induced charge-transport modification and OIP insulation degradation, and may support the condition assessment and maintenance of underground cable insulation systems.