Discharge Inception Characteristics Analysis of Epoxy / Silica Nanocomposites in SF6 Gas using Volume-time theory

This paper reports comparison of measured results of partial discharge inception voltage (PDIV) of epoxy/silica (EP/SiO
₂
) composites sample in SF
₆
gas with estimated one derived from Volume-time theory. The discussion is made to elucidate mechanism of discharge inception in the wedge gap formed between the solid insulation material and SF
₆
gas. Namely, the dependence of the PD occurrence probability on the applied voltage was calculated using Volume-time theory and compared with measured one. Results show that without assuming electron emission from the solid insulator surface, the voltage dependence of the PD occurrence probability derived from the Volume-time theory agrees well with measured one at the voltage below 30 kV, while they do not match at higher voltage. Calculated results in assuming the electron emission from the solid insulator surface are also found to agree with measured ones in all the voltage region considered. This agreement demonstrates the validity of the Volume time theory that EP and EP / SiO
₂
initiate a discharge in SF
₆
by emitting initial electrons from the insulator surface as well as electron detachment from SF
₆
- ions. These results suggest that discharge initiation can be suppressed by increasing the ionization energy by adding the SiO
₂
nanofiller to EP.