Enhanced stability nanofluids for sustainable high-voltage transformer applications

Abstract

The demand for sustainable alternatives to fossil-based insulating liquids in power transformers has intensified due to environmental concerns associated with mineral oils. Natural esters, such as canola oil, are renewable and biodegradable insulating liquids, but their adoption remains limited due to poor thermo-oxidative stability, ionization resistance, and standardization. To address these limitations, this study presents the development and characterization of a canola-based nanofluid enhanced with TiO₂ nanoparticles to improve its suitability for transformer insulation. TiO₂ nanoparticles with an average size of 5 nm were dispersed into canola oil using two surfactants, Polysorbate 80 and Span 80, at concentrations ranging from 2 g/L to 8 g/L. The novelty of this work lies in the use of ultra-fine (5 nm) TiO₂ nanoparticles combined with a comparative optimization of surfactant type and concentration to achieve long-term colloidal stability and improved dielectric performance, an approach previously unreported in this context. Nanofluid stability was assessed via turbidity measurements and visual inspection, with Span 80 demonstrating superior long-term stabilization. Results show that nanoparticles and surfactant addition slightly increased the density and viscosity of the base oil but remained within acceptable limits for transformer applications. Dielectric analysis revealed a reduction in dissipation factor with the addition of nanoparticles, with optimum performance at 0.2 wt% of nanoparticles and 2 g/L of surfactant. Furthermore, the AC breakdown voltage improved by 27.01 % at an optimal formulation of 0.2 wt% TiO₂ and 2 g/L Span 80. The developed nanofluid demonstrates strong potential as a sustainable and high-performance alternative to mineral oil for next-generation transformer applications.