Effect of Bending Deformation on Electrical Tree Properties of Polypropylene Copolymer and Blend Insulation for HVDC Cables

This article investigates the effect of bending deformation on the electrical tree degradation characteristics of polypropylene (PP) copolymer and blend insulation. Electrical tree growth experiments are conducted under various bending curvature radii and temperatures. The results indicate that bending deformation promotes the initiation and accelerates the growth of electrical trees. At 30 °C, the initiation time of PP homopolymer (PPH) electrical trees with a curvature radius of 10 mm is reduced by 89.4% compared to the unbent sample. Under extreme bending deformation, PPH tends to develop a straight-stick electrical tree morphology. Conversely, the presence of elastic phases introduced by copolymers and blends increases electrical tree dispersion at elevated temperatures and suppresses the tendency to develop along a straight line. Simulation and microscopic tensile experiments demonstrate that blended samples will not form significant physical defects under large deformation, unlike the other two samples. The enhanced mechanical properties support the excellent electrical tree resistance of blended samples under bending deformation, making them promising for insulation in bending conditions.