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In this research, a vegetable-based oil blend has been subjected to thermal ageing for different time periods before and after being dispersed with graphene oxide nanoparticles and its dielectric breakdown is investigated and compared with the newly developed unaged samples. Results show that at peak values, the ac breakdown voltage of nanofluids decreases by just 2.6% after ageing when compared to the base oil for which the ac breakdown voltage decreases by 8.4% after ageing. Similarly, at peak value, the impulse breakdown voltage of nanofluid decreases by just 2.9% after ageing as compared to the base oil for which the impulse breakdown voltage decreases by 7.3%. Thus, the developed nanofluid can be potentially used in transformers with successful operation after analyzing the physio-thermal properties. [ABSTRACT FROM AUTHOR]

Graphene oxide is one of the latest in- trend nanomaterials in the field of nanotechnology which is being studied in various engineering fields. Yet, its effects on the transformer solid insulation remain unexplored. In this research, the transformer pressboard and Kraft paper are impregnated with nonconductive graphene oxide dispersed vegetable ester-based insulating nanofluid and the behavior of impregnated solid insulation is studied under different thermal aging conditions. The results show that after 60 days of aging, the crystallinity of nanofluid impregnated pressboard is 24.9% more than that of the base oil-blend (OB) impregnated pressboard whereas the crystallinity of nanofluid impregnated Kraft paper is 3.8% more than that of the base OB impregnated Kraft paper. In terms of dielectric properties, the ac breakdown voltage (BDV) of nanofluid impregnated pressboard and Kraft paper is 29.5% and 41% more than the OB impregnated pressboard and Kraft paper, respectively. The dielectric stress is more uniform in nanofluid-based insulation system as compared to the base OB-based insulation system leading to a better design clearance. Therefore, graphene oxide dispersed ester oil (EO)-based nanofluid impregnated solid insulation has better mechanical and dielectric properties, thus leading to an increased lifespan of the transformer. [ABSTRACT FROM AUTHOR]

In this work, graphene oxide nanoparticles are dispersed in different concentrations in a soyabean extracted natural ester-based oil-blend having mineral oil as secondary oil and the resulting nanofluids are tested for various dielectric and physio-thermal properties. The results show that with the addition of nanoparticles, the breakdown voltage of nanofluids increases up to 42% as compared to pure mineral oil, 17% as compared to pure ester oil and 15% as compared to the base oil-blend. Relative permittivity and dissipation factor parameters follow a similar trend as well. Thus, the prepared nanofluids can be used as alternative insulating oils in place of the conventional mineral oil in oil-filled transformers. [ABSTRACT FROM AUTHOR]

• Bio-degradable vegetable-based oils are 3rd generation insulating fluids in order to replace conventional mineral oil. • Dispersion of TiO 2 and ZnO results in enhancement of dielectric properties of vegetable oil based oil-blends. • Detailed statistical analysis of Weibull data regarding the failure probabilities confirms the experimental results. • TiO 2 and ZnO dispersed vegetable oils can be used as insulating fluids to improve the rating of transformers. Mineral oil being the most extensively used oil in transformers still has some associated drawbacks like non-biodegradability and low fire point. Bio-degradable, non-toxic and fire-resistant vegetable-based ester oils are considered as second-generation insulating fluids. These oils are continuously being tested in order to replace the conventional mineral oil for insulation purposes. The dielectric properties of these vegetable oils are further improved by adding various types of nanomaterials. This paper focuses on preparing a mixture of natural ester oil and mineral oil blend as a base fluid and studying the dielectric behavior of this fluid after being dispersed with TiO 2 and ZnO nanoparticles. Results indicated that dispersion of both nanomaterials resulted in an overall enhancement in the dielectric properties of nanofluids. The breakdown voltage of TiO 2 dispersed nanofluid is reported to be about 30% greater than pure mineral oil, 24% greater than pure ester oil, and 17% greater than the oil-blend. Likewise, the breakdown voltage of ZnO dispersed nanofluid is observed to be around 28% greater than pure mineral oil, 19% greater than pure ester oil, and 16% greater than the oil-blend. Moreover, in terms of cooling, TiO 2 dispersed oil-blend shows better performance as a coolant. Thus, both types of nanofluids can be used as insulating oils in the transformer depending upon the requirements expected to be met by the transformers. [ABSTRACT FROM AUTHOR]