Effects of Ferromagnetism Particles on Electrical Tree Growth in Epoxy/Fe 3 O 4 Composites in Magnetic Field

In this paper, Fe 3 O 4 particles with different diameters are added to epoxy resin. Dielectric properties and the electrical tree growth characteristics of the specimens are tested in magnetic field. Experimental results show that magnetic field leads to higher charge carrier mobility and more serious electrical tree degradation. The addition of ferromagnetism particles with a diameter of 20 nm generates more deep traps and causes the decrease of conductivity. Moreover, nanocomposites show great inhibition effect to electrical tree whether high magnetic field is applied. Particles with a diameter of 500 nm play a role as scattering center of electrical tree and cause larger damage area. Ferromagnetism particles with a diameter of $30\ \mu\mathrm{m}$ induce local magnetic field and electric field concentration, accelerating the growth of electrical tree. Quantum chemical and electrodynamics calculation are combined to analyze the energy level distribution and the charge carrier dynamic behavior in high magnetic field. Changes in electrical tree growth result from the size effects of Fe 3 O 4 particles, including changing relative permeability, as well as acting as exciton killer, scattering center and weak points.