Breakdown Strength Influences of Titanium Dioxide Nanoparticles on Midel Canola-Based Natural Ester oil: A Comparison Between the Anatase and Rutile Phases of Titanium Dioxide

Abstract

Natural ester oils are an alternative solution for sustainable transformer insulation. They offer good dielectric properties and in addition improve safety of equipment and sustainable environment. They have higher fire resistance than the widely used mineral oil and are less prone to explosions. They are also highly biodegradable and renewable. However, some challenges such as inconsistent breakdown voltage at higher temperatures and higher streamer speeds hinder the wide use of natural esters. Nanotechnology has been found to improve the properties of the oil, including the breakdown voltage. Different nanoparticles have been previously studied, giving varying results. This dissertation presents a study of the use of two phases of TiO2 nanoparticles, namely rutile and anatase, to improve the breakdown voltage of natural ester oil at higher temperatures. The study seeks to find the effects of the nanoparticle phases on the oil under uniform and non-uniform electric fields. Nanofluids of different loading concentrations (0.01 vol%, 0.03 vol%, 0.05, vol%) were created in each nanoparticle phase for the purpose of the study. The findings are that both phases of the nanoparticles improve the breakdown voltage under uniform fields. The anatase portrayed an impressive improvement of 85% at ambient temperature, while the rutile phase enhanced by 61%. At higher temperatures however, the rutile phase had better improvement. Rutile TiO2 nanoparticles consistently outperformed the anatase phase in improving the breakdown voltage at higher temperatures. Under non-uniform electric fields, the rutile TiO2-based nanofluid was found to be superior to the anatase-based fluid. Rutile TiO2 resulted in a significant 10% improvement in the average breakdown voltage and streamer acceleration voltage. An overall decrease in the streamer speeds was observed with the addition of the rutile TiO2 nanoparticles. In contrast, anatase TiO2 resulted in decreased breakdown voltage and increased streamer speeds when compared to both the rutile nanofluid as well as the pure natural ester oil. The rutile phase of TiO2 can be regarded as a feasible solution for breakdown voltage improvement of natural ester oil in both cases of uniform and non-uniform electric field. The effects are attributed to the electron capture phenomenon and the good thermal stability of rutile TiO2. A stable composite is formed between the rutile nanoparticles and the host natural ester. The resultant morphological structure enables stable interfacial regions even at higher temperatures. In conclusion therefore, rutile TiO2 nanocomposite natural fluid is a possible solution to the current limitations in ester oils as power transformer insulation oil alternative.