Effects of magnetic field direction on treeing behavior of silicone rubber

Research is undertaken in this paper to clarify the effect of magnetic field (MF) direction on electrical tree propagation in silicone rubber (SiR). Needle-plate electrode is employed in the experiment. To avoid magnetic field stress on the needle electrode, this paper choose silver needles as the needle electrode, and previously placed in style. The dimension of sample is 10 mm × 10 mm × 20 mm. The distance between needle-plate electrode is 2 mm. Both repetitive pulse voltage and AC voltage is employed in the experiment. To study the effect of MF direction on the growth of electrical tree, the morphology of the electrical tree is observed from the direction of the MF and perpendicular to the MF, respectively. And the fractal dimension of the electrical tree under pulse voltage is analyzed. Obtained results show that under AC voltage, the tree morphology from two directions are similar with the increase of the magnetic flux density (MFD). Under pulse voltage, the increase of MFD can promote the growth of electrical tree in two directions. The promoting effect of the MF on the electric tree is stronger in the direction of the MF than that perpendicular to the MF.