Comparison of Bulk and Surface Modification of Epoxy Resin Towards Enhanced Surface Flashover Performance

The basin insulator inside gas-insulated switchgear (GIS) is highly susceptible to surface discharge, particularly at the gas-solid interface. This work compares bulk and surface modifications of epoxy resin (EP) in enhancing surface discharge resistance. Modifications including nano TiO₂ doping (1 wt%~5 wt%) and surface fluorination treatment (at temperatures from 25 to 85℃) are applied for investigating dielectric and surface discharge performances. The results indicate that the 1% TiO₂ composite exhibits the most significant improvement in electrical performance with the first flashover voltage increasing from 34.4 to 42.4 kV, while the highest increase in flashover due to fluorination occurs in samples treated at 25°C, from 34.40 to 39.40 kV, both under negative impulse voltage. Moreover, resistivity and dielectric constant characteristics of epoxy resin are investigated, which exhibit similar trends with surface discharge, suggesting that the effect of modification on flashover properties may be attributed to charge trapping and transport characteristics in the EP composites. Generally, nano doping is a more effective method to elevate surface discharge performance of EP in contrast to fluorination. However, it is noted that enhanced resistance to flashover by nano doping may compromise its mechanical performance.