Effects of Particle Dispersion on EL Inception and Extinction Fields of TiO2/Epoxy Nanocomposites

It has been revealed that the ac breakdown strength of TiO2/epoxy nanocomposites, with good particle dispersion, is higher than that of unfilled epoxy resin. Here, the electroluminescence (EL) inception and extinction fields of TiO2/epoxy nanocomposites with varying particle dispersion states were examined to explain the mechanism underlying the breakdown strength enhancement. The findings revealed that the EL inception and extinction fields of TiO2/epoxy nanocomposites, with high particle dispersion, exceeded those of the unfilled epoxy resin, probably because the nanoparticles prevent the movement of electrons to gain energy. Conversely, TiO2/epoxy nanocomposites that contain agglomerates exhibit almost the same or lower EL inception and extinction fields compared to those of the unfilled epoxy resin. This is attributed to the acceleration of electrons to gain energy in the broad region of a high electric field surrounding the agglomerates.

I. Introduction

Epoxy resin is employed as a solid insulating material inside power apparatuses, such as generators, transformers, and switchgears [1]. Enhancing breakdown strength increases the operating electric field, thereby contributing to the development of high-efficiency generators and compact solid switchgears. One technology that improves the breakdown strength of epoxy resins involves the use of nanocomposites in which nano-sized ceramic particles are dispersed throughout the epoxy resin. Epoxy nanocomposites are recognized for their excellent insulation performance, including superior breakdown strength and resistance to partial discharges [2]. Application of epoxy nanocomposites in generators and solid switchgears has also been proposed [3], [4].