Enhancement of Electrical Tree Resistance of Epoxy Insulation under Bipolar Square Wave Voltage by Micro-SiO2 Doping

In this paper, epoxy resin composites doped by 60 wt% of micro SiO
2
fillers are prepared. The effects of micro-SiO
2
doping on the electrical tree characteristics under bipolar square wave voltage, thermal conductivity, thermal stability, and trap characteristics of epoxy resin are investigated. The results show that the withstanding time of epoxy resin exposed to the electrical tree is improved by doping of micro-SiO
2
, especially at 10 kHz where the withstanding time is increased from 6 min to 44 min. Enhanced thermostability and thermal conductivity, as well as more deep-level traps are also obtained, which furtherly reduce the chain degradation of epoxy resin at elevated temperatures. It is deduced that the doping of micro-SiO
2
can effectively improve the electrical tree resistance properties of epoxy resin under bipolar square wave voltage. An elevated temperature can lead to decreased withstanding time of the epoxy composite which drops sharply beyond the glass transition temperature.