Impact of cellulose contamination and flow velocity on dielectric properties of synthetic ester-based nanofluid

• Impact of cellulose contamination on dielectric strength in transformer oils. • TiO₂ nanoparticles enhance dielectric properties of synthetic ester oils. • Increased fluid circulation velocity improves dielectric performance and stability. • Nanofluids mitigate cellulose-induced degradation and boost breakdown voltage. This study proposed a novel investigation into the combined effects of fluid circulation velocity and cellulose particle contamination on the dielectric performance of insulating oils, a relationship that has been infrequently explored. A direct comparative analysis was conducted between pure synthetic esters and ester-based nanofluids (with 0.01 % TiO₂ nanoparticles). Dielectric characteristics were rigorously assessed using partial discharge (PD) tests and breakdown voltage (BDV) measurements under controlled conditions. Specifically, these tests were performed while systematically varying both the fluid circulation speed and the concentration of introduced cellulose contaminants, allowing for a direct comparison of their influence on both the pure ester and nanofluid. The experimental results clearly demonstrate the detrimental impact of cellulose particles on the dielectric strength. Conversely, increasing the fluid circulation speed consistently improved the dielectric performance, as evidenced by the higher PDIV and BDV values and lower discharge intensity across both fluid types. Furthermore, the ester-based nanofluid consistently exhibited superior dielectric properties compared to the pure ester under all tested conditions, suggesting the beneficial role of TiO₂ nanoparticles in mitigating the negative effects of cellulose contamination and enhancing the overall dielectric performance.