Partial Discharge Inception Voltage Characteristics for Nano-micro Composites under Impulse Voltage in SF6 Gas

The authors have investigated effect of epoxy resin nanocomposites on improvement of creepage discharge withstand voltage so as to reduce the size of the gas insulated switchgear (GIS). This paper deals with the effect of nanofiller loading into microcomposite on partial discharge inceptio voltage (PDIV) in SF ₆ gas under standard lightning impulse voltage application using an electrode system with wedge gap. The influence of the nanofiller on the dielectric properties and the electric field distribution around the wedge gap was investigated in order to understand this discharge mechanism. As a result, PDIV in a model electrode with a wedge gap improved with small amounts of nanosized silica and titania, and decreases with strontium titanate. The higher the relative permittivity of the insulator, the larger the value of the sample surface electric field around the wedge gap. Nano-micro composites(NMC) containing silica or titania are found to provide higher PDIV than the microcomposite MC, while the NMC have higher relative permittivity than the MC and enhance the electric field in the wedge gap. The increase in PDIV of NMC is interpreted to be due to suppression of electron emission from the sample surface, which is brought by the nanofiller to give rise to deep electron trap level.