Impact of Repeated Impulse Voltage on the Breakdown and Space Charge Characteristics of Polypropylene for High-Voltage Cable Insulation

Polypropylene (PP) exhibits excellent electrical insulation properties, recyclability, and high-temperature stability, making it a eco-friendly material for high-voltage cable insulation. Repeated impulse voltages (such as those generated by lightning strikes and switching operations) may cause degradation of polypropylene insulation and compromise its reliability. This study investigates the breakdown characteristics and space charge accumulation patterns of polypropylene insulation materials under repeated impulse voltages. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5 0 \%}$</tex> impulse breakdown voltage of the material was measured using the step-up method, and an exponential relationship model was established between the amplitude of the impulse voltage and the average number of pulses required for breakdown to occur. Pulse electroacoustic (PEA) testing and analysis were conducted to examine the space charge distribution characteristics of the material under a direct current high-field environment after exposure to different numbers of impulse voltages <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{0}, \mathbf{5 0}, \mathbf{1 0 0}, \mathbf{2 0 0}$</tex> times). The results indicate that when the number of impulse voltages reaches 100 or more, significant space charge accumulation occurs near the cathode inside the material, and this phenomenon further intensifies when the number of impulse voltages increases to 200. The study reveals a significant correlation between the number of impulse voltages and space charge accumulation, providing experimental evidence and references for optimizing the impact resistance of polypropylene insulating materials.