Abstract
To date, breakdown voltage is an underlying risk to the epoxy-based electrical high voltage (HV) equipment. To improve the breakdown strength of epoxy resin and to explore the formation of charge traps, in this study, two types of polyhedral oligomeric silsesquioxane (POSS) fillers are doped into epoxy resin. The breakdown voltage test is performed to investigate the breakdown strength of neat epoxy and epoxy/POSS composites. Electron traps that play an important role in breakdown strength are characterized by thermally stimulated depolarized current (TSDC) measurement. A quantum chemical calculation tool identifies the source of traps. It is found that adding octa-glycidyl POSS (OG-POSS) to epoxy enhances the breakdown strength than that of neat epoxy and epoxycyclohexyl POSS (ECH-POSS) incorporated epoxy. Moreover, side groups of OG-POSS possess higher electron affinity (EA) and large electronegativity that introduces deep-level traps into epoxy resin and restrain the electron transport. In this work, the origin of traps has been investigated by the simulation method. It is revealed that the functional properties of POSS side group can tailor an extensive network of deep traps in the interfacial region with epoxy and enhance the breakdown strength of the epoxy/POSS nanocomposite.
Highlights
With growing direct current high voltage (HVDC) applications, insulation failure has attracted much attention for epoxy-based insulating equipment to ensure power system reliability [1]
Incorporating polyhedral oligomeric silsesquioxane (POSS) to epoxy can enhance the electrostatic potential and electron affinity for charge carriers, as compared to ECH-POSS. These factors increase the deeper traps of EP/octaglycidyl POSS (OG-POSS) and result in higher breakdown strength
The results show that doping of the OGPOSS filler improves the trap level and electron affinity (EA), which eventually enhances the DC breakdown strength
Summary
With growing direct current high voltage (HVDC) applications, insulation failure has attracted much attention for epoxy-based insulating equipment to ensure power system reliability [1]. The breakdown performance of epoxy resin can be improved by nanoparticle incorporation, but the mechanism of breakdown relates to interfacial properties is still unclear. In the interfacial region of nanocomposites, the dielectric strength is influenced by several factors, i.e., molecular chain dynamics, carrier traps, potential barrier of polymer structure against the charge transport, etc. Wang et al studied the DC breakdown characteristics of LDPE/Al2 O3 nanocomposites and found that the DC breakdown strength was dominated by deep trap level, which is improved by the incorporation of nanoparticles [9]. The traps can be tailored by incorporating conventional nanoparticles to enhance the breakdown strength of base polymers [11,12,13]. Surfaces are treated with silane, grafting, and plasma treatment is utilized with varying degrees of achievement [14,15,16]
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