Electrical Treeing Behavior and Breakdown Characteristics of Polypropylene Cable Insulation Under Mechanical Stress and Low-Temperature Conditions

This paper investigates the effect of mechanical stress at low temperatures on the electrical treeing behavior and breakdown characteristics of PP insulation. The results demonstrate that as mechanical stress increases, the breakdown strength of the samples significantly decreases, with a more pronounced reduction at lower temperatures. Additionally, with increasing mechanical stress and decreasing temperature, the microstructure of material becomes more severely damaged, leading to enhanced electrical tree degradation and partial discharge in PP insulation. The electrical tree in the sample with an elongation of 15 % at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-40^{\circ} \mathrm{C}$</tex> exhibits the most significant degradation, with its morphology transitioning from a branchlike structure to a bush-branch-like structure.