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In the last decades, vegetable-based insulating liquids, derived from plant seeds, have emerged as an environmentally friendly alternative to traditional petroleum-based mineral insulating oils. These vegetable oils exhibit excellent characteristics for high-voltage insulation, including remarkable high-temperature stability, as evident in their flash and fire points. Furthermore, their high water absorption capacity may serve to safeguard the integrity of paper insulation within transformers. However, their practical application is limited to sealed transformers due to their susceptibility to oxidation. Additionally, using these oils in regions with low temperatures presents challenges because of their poor flow properties under cold conditions. Canola oil, derived from canola seeds, offers a balanced set of properties, particularly concerning pour point and oxidation stability, attributable to its unique fatty acid composition. This study reviews deeply into the potential, prospects, and possible enhancements that can be applied to canola oil. Significant tutorial elements as well as some analyses are included. The aim is to reveal the deep attributes of canola oil as a suitable insulating liquid for both free-breathing and hermetically sealed transformers, while also ensuring it serves as an efficient cooling medium for transformers operating in extremely cold environments. Of the many properties examined, this review pays particular attention to oxidation stability and the flow characteristics of the oil. • Plant-based insulating liquids are environmentally friendly and sustainable. • Canola oil is a potential alternative to mineral-based insulating liquids. • Cooling and oxidative stability enhancement of plant-based oil for insulation. • Useful life, recyclability, and advantage of canola oil in transformer insulation. [ABSTRACT FROM AUTHOR]

• Vegetable insulating liquids are potential alternative to mineral insulating oil. • Application of nanoparticles enhances the properties of vegetable insulating liquid. • The utmost problem of nanofluids is long-term stability. • Enhancing nanofluid stability through steric and electrostatic approaches. • Physicochemical and dielectric properties of nanofluid from different nanoparticles. The utilization of nanotechnology to enhance the properties of liquids has been underway for several decades. The systematic incorporation of nanoparticles into the base liquids has demonstrated its effectiveness in improving the thermoelectrical properties of insulating liquids. Vegetable-based liquids have emerged as potential alternatives to mineral-insulating oil due to the environmental concerns associated with the latter, despite their excellent electrical properties. Despite the environmental friendliness and health safety attributes of vegetable-based liquids, there are yet some limitations like low ionization resistance, high dielectric losses, low volume resistivity, and poor oxidation stability. These limitations are currently being addressed using different nanoparticles by the addition of an appropriate concentration to the base liquids. Though there is development in the synthesis of nanofluids using different nanoparticles for transformer insulation, no nanoparticle has been declared as one with ultimate performance. This review presents a comprehensive examination of recent findings in the literature concerning the use of nanofluids for transformer insulation, focusing specifically on the challenge of long-term stability. The review addresses various aspects including the characterization of nanoparticles, types of nanoparticles employed for enhancing insulating liquids, methods for preparing nanofluids, strategies for improving nanofluid stability, the impact of nanoparticles on vegetable-based insulating liquids, and the existing challenges associated with nanofluids. The report investigates these topics extensively, presenting a thorough analysis of the subject matter. It aims to provide valuable insights to researchers in this field and to encourage the exploration of sustainable and environmentally friendly insulating liquids suitable for green transformers. [ABSTRACT FROM AUTHOR]

• The influence of nanoparticles on the dielectric properties of neem oil was investigated. • Dielectric properties of the base liquid increases with nanoparticles loading. • Effect of temperature on the dielectric loss of the nanofluids was investigated. • The compatibility test of the nanofluid with kraft paper was investigated. • Nanofluid has no pronounce effects on the dielectric properties of kraft paper. Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO 2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO 2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO 2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied. [ABSTRACT FROM AUTHOR]

• The influence of nanoparticles on the dielectric properties of neem oil was investigated. • Dielectric properties of the base liquid increases with nanoparticles loading. • Effect of temperature on the dielectric loss of the nanofluids was investigated. • The compatibility test of the nanofluid with kraft paper was investigated. • Nanofluid has no pronounce effects on the dielectric properties of kraft paper. Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO 2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO 2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO 2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied. [ABSTRACT FROM AUTHOR]