Study on the Space Charge Characteristics of Polypropylene Insulation Material Under a Polarity Reversal Electric Field.

High-voltage (HV) cables may experience voltage polarity reversal during power adjustment, leading to the accumulation of space charges inside the insulation material and causing distortion of the internal electric field. To characterize the effect of grafting modification on the insulation properties of polypropylene (PP), various electrical properties were characterized. The results show that grafting modification can significantly improve the electrical properties of PP, with PPG-2 exhibiting the best electrical properties. Compared with PP, the breakdown strength of PPG-2 is increased by 39.27%, and the critical electric field is increased by 36.52%. Meanwhile, the charge accumulation inside the PPG-2 is extremely small after voltage polarity reversal. The mechanism of grafting modification to enhance the electrical properties of PP was explained by analyzing the trap characteristics of the samples. This indicates that grafting modification introduces a large number of deep traps within PP, suppressing the injection and migration of charge carriers. The presence of deep traps weakens the charge accumulation and electric field distortion at the interface. In this paper, the optimal monomer and content of grafted PP were determined, and the insulation properties of the cable under operating conditions were analyzed. The research results offer practical guidance for the development of high-performance grafted PP cable insulation materials and the reliability of cable operation.