Investigations on the effect of ageing on charge de-trapping processes of epoxy–alumina nanocomposites based on isothermal relaxation current measurements

• Published in: IET Nanodielectrics Vol. 3; no. 4; pp. 116 - 123
• Main Authors: Maur, Subhajit, Haque, Nasirul, Pottekat, Preetha, Chakraborty, Biswajit, Dalai, Sovan, Chatterjee, Biswendu
• Format: Journal Article
• Language: English
• Published: Beijing The Institution of Engineering and Technology 01.12.2020; John Wiley & Sons, Inc; Wiley
• Subjects: Accumulation; ageing; ageing conditions; Aging; Aging (materials); Al2 O3; alo; alumina; Aluminum oxide; charge formation; Charge materials; Depolarization; dielectric material; dielectric materials; Dielectric properties; dipolar relaxation; Direct current; electric current measurement; Electric fields; Electrodes; Energy; epoxy insulation; epoxy-alumina nanocomposites; epoxy-based nanocomposites; high-voltage direct current environment; HVDC environment; Insulation; insulation health; Investigations; IRC measurements; isothermal relaxation current measurements; Nanocomposites; Nanoparticles; PDC measurements; polarisation-depolarisation current measurements; Research Article; shallow traps; Space charge; space charge accumulation; thermal ageing; Thermal degradation; trap distribution characteristics; Trapped charge; trapped charge accumulation; Trapping; ageing conditions; epoxy insulation; HVDC environment; dielectric materials; dipolar relaxation; nanocomposites; Al2O3; charge formation; alumina; nanoparticles; thermal degradation; space charge; PDC measurements; epoxy-based nanocomposites; ageing; trapped charge accumulation; epoxy-alumina nanocomposites; IRC measurements; isothermal relaxation current measurements; insulation health; polarisation-depolarisation current measurements; thermal ageing; space charge accumulation; dielectric material; electric current measurement; high-voltage direct current environment; trap distribution characteristics; shallow traps
• ISSN: 2514-3255; 2514-3255
• DOI: 10.1049/iet-nde.2020.0020

In this study, the relationship between thermal ageing and charge trapping properties of epoxy-based nanocomposites has been investigated. With ageing, any dielectric material undergoes thorough degradation. This degradation significantly affects the space charge accumulation and charge trapping behaviour of the dielectric, which are very important parameters for insulation health under high-voltage direct current (HVDC) environment. In this work, an improved model based on the isothermal relaxation current (IRC) has been developed to study the charge trapping behaviour of pure epoxy and epoxy alumina (Al2O3) nano-composites at different ageing conditions. A methodology based on polarisation–depolarisation current (PDC) measurements has been proposed to identify the current component due to a dipolar relaxation in measured total IRC. This will help to identify the trap distribution characteristics more accurately compared to conventional IRC measurements. It was experimentally observed that the addition of nanoparticles significantly reduces trapped charge formation and reduces thermal degradation. It is observed that aging leads to the generation of deeper traps, while the addition of Al2O3 nanoparticles mainly enhances the density of shallow traps. Results presented in this work indicate that epoxy–alumina nanocomposites are very much suitable in HVDC applications from the perspective of trapped charge accumulation.