Effect of β‐Crystal on Electrical Tree Growth and Breakdown Characteristics of Polypropylene Cable Insulation Under Mechanical Stress

ABSTRACT This paper investigates the effect of β‐crystal on the electrical tree growth and breakdown characteristics of polypropylene (PP) cable insulation under mechanical stress. Mechanical stress promotes the growth of electrical trees and reduces the breakdown strength of PP insulation. When mechanical stress is applied, electrical trees exhibit a more dispersed distribution, with a notable expansion of the damaged area, evolving into a bush–branch configuration. β‐crystals enhance the mechanical properties of PP insulation, effectively suppressing electrical tree degradation and partial discharge (PD) under mechanical stress. Compared to stressed PP/0 (PP insulation containing 0 wt% β‐nucleating agent), the cumulative damage area of stressed PP/0.2 (PP insulation containing 0.2 wt% β‐nucleating agent) decreases by 0.137 mm 2 and the maximum PD amplitude is reduced by 493.2 pC. Moreover, β‐crystals mitigate the reduction in breakdown strength of PP insulation under mechanical stress. Among all samples, PP/0.2 exhibits the smallest reduction in breakdown strength, showing a 30.90% improvement over stressed PP/0 at 30°C. The inclusion of 0.2 wt% β‐nucleating agents effectively suppresses the growth of electrical trees and mitigates the reduction in breakdown strength of PP cable insulation under mechanical stress, thereby improving the stability of PP insulation in stress environments.