Dielectric and Thermal Ageing Characteristics of Al₂O₃ Nanofluid-Impregnated Cellulose for Power Transformer Applications

As nanotechnology progresses, nanofluids have emerged as promising candidates for transformer insulation due to their enhanced dielectric and thermal properties. This study evaluates the degradation behavior of a mineral oil-cellulose system compared to an alumina (Al2O3) nanofluid-cellulose system. Accelerated thermal ageing tests were conducted at 120°C for a 20-day duration, simulating approximately 20 years of field service. Key findings reveal that the nanofluid-impregnated paper exhibited superior mechanical longevity, characterized by a 3% reduction in the tensile strength deterioration rate relative to mineral oil samples. Initially, the AC breakdown voltage (BDV) of the nanofluid was 10.85% higher than that of the base mineral oil; however, a more pronounced decline was observed after 14 days, primarily attributed to nanoparticle agglomeration. Despite a marginal 3% increase in kinematic viscosity, the nanofluid maintained acidity levels within acceptable operational limits (< 0.2 mg KOH/g). These results demonstrate that while Al2O3 nanofluids significantly extend the thermal life of solid insulation, long-term colloidal stability remains a critical constraint for practical transformer applications.