Effect of magnetic field on tree characteristics in silicone rubber

Silicone rubber (SiR) has been an important material widely used in the cable accessories in cross-linked polyethylene (XLPE) cables. The electrical tree is a serious threat to SiR insulation and it will cause breakdown when reaches the ground. The high carrying capacity of superconducting cable makes the magnetic flux density up to hundreds of mT around the conductor. However, the effect of high magnetic flux density on electrical tree in SiR has not been researched. In this paper, the magnetic flux density ranged from 0 to 400 mT. The electrodes were typical needle-plate electrodes. The frequency of the applied AC voltage was 50 Hz. The growth process of electrical tree was recorded by a microscope system and the pictures were taken. The experiment result indicated that the high magnetic flux density changes the tree structure and affects the growth of tree length and width.