Understanding charge trap characteristics of epoxy nanocomposite under steep fronted lightning impulse voltage

Charge trap characteristics of epoxy spacer insulating material due to surface flashover are important for improving the stable operation of GIS. In this work, magnesium oxide (MgO) filled epoxy nanocomposite material is proposed as the spacer material and its performance is compared with pure epoxy. The surface properties of spacer materials were altered using surface flashovers generated due to standard lightning impulse (LI) and steep fronted lightning impulse (SFLI) having front time of 0.1 µs, using rod plane electrode setup. The impact of surface flashovers on charge trap characteristics were analysed through surface and space charge studies. The surface charge behaviour was estimated by surface potential decay and their trap characteristics, space charge accumulation was measured using pulsed electro acoustic technique. SFLI flashover voltage was lower compared to LI voltages and MgO filled epoxy nanocomposite had higher flashover voltage compared to pure epoxy. The space charge density of MgO filled epoxy nanocomposite was less compared to pure epoxy after treating with LI/SFLI flashover voltages. MgO filled epoxy nanocomposite had enhanced surface potential decay and reduced trap energy after surface flashover. Due to the superior insulating properties, MgO filled epoxy nanocomposite can be used as the spacer material in GIS components.