Effects of Gradient Magnetic Field on Electrical Tree Growth of SiR/Graphene Nanocomposites

In this article, an unevenly distributed gradient magnetic field is constructed. The electrical tree characteristics in silicone rubber (SiR) under a gradient magnetic field are investigated. The cumulative damage is increased by 365% under $\Delta 1.5$ T and by 411% under $\Delta -1.5$ T gradient magnetic field. A modification method based on graphene nanosheet doping is proposed to improve the insulation performance of the SiR under a gradient magnetic field. With the introduction of an appropriate amount of graphene nanoparticles, the damage area of the SiR/graphene nanocomposites is reduced to 19.9% in the nonmagnetic field, and is reduced to 17.4% and 14.0% under $\Delta \pm 1.5$ T gradient magnetic field, respectively. The time to breakdown is extended by 40%–84%. The experimental results show that the magnetic field can affect the charge behavior and enhance the electric field near the electrode. The growth of the electrical tree is accelerated due to the enhanced partial discharges (PDs). The graphene nanosheets reduce the interface electric field and inhibit the growth of electrical trees by capturing the injected charges.