Dielectric properties and PD resistance of epoxy/fumed and precipitated silica and alumina nanocomposites

Epoxy/fumed and precipitated silica and alumina nanocomposites were evaluated on their dielectric properties and partial discharge (PD) resistance. Dielectric properties, i.e., permittivity and dissipation factor tanδ were measured in the frequency range from 20 Hz to 1 MHz. PD resistance was assessed using a rod-to-plane electrode with an air gap 0.2 mm under 4 kV_rms. A new discovery was made for moisture and chemical residue effects for the dielectric properties. Natural moisture would not affect much permanent dielectric properties. It was elucidated that nano filler addition would enhance PD resistance, as expected. Furthermore, it was found that epoxy/silica nanocomposite is better in PD resistance than epoxy/alumina nanocomposite. Filler preparation methods, i.e., fumed and precipitated, might influence both properties.