Space Charge Characteristics of Epoxy/BN@SiO₂ Nanocomposites Used in Solid State Transformer

The developments of high-power density solid state transformer (SST) give rise to the urgent requirement of the high performance insulating material, such as the epoxy resin solid insulation. Modification of epoxy resin for superior insulation and heat dissipation properties is of great importance to the insulation design in SST. Space charge is a main factor to threat the insulation under high electric stress. This paper studies the space charge characteristics of Epoxy/BN@SiO2 nanocomposites, which is potential to use in SST. Initially, we prepared the SrO₂-coated BN nanoparticles (BN@SiO₂) by tetraethyl orthosilicate (TEOS) surface modification. After that, the EP/BN@SiO₂ nanocomposites were prepared by a mixed dispersion and curing process with different nanofiller loadings. Next, the microstructure and physicochemical performance of the nanocomposites were characterized by infrared spectroscopy, scanning electron microscopy (SEM), energy spectrum analysis and transmission electron microscopy (TEM). Most importantly, space charge distributions of the EP/BN@SiO₂ nanocomposites were measured and analyzed by pulse electroacoustic method (PEA). The results indicated that SiO₂ was successfully grafted on the surface of BN after surface modification. The addition of BN@SiO₂ nanoparticles can effectively reduce the space charge accumulation under the electric fields of 20 and 40 kV/mm. It is concluded that the trapping sites are introduced at the interface between the BN@SiO₂ nanoparticles and epoxy resin. It contributes to the reduction of charge injection and space charge accumulation. This work provides an insight to the design and application in high power density SST insulation.