This review is focused on the research of dielectric fluids, especially commonly used power transformer oils enhanced by nanoparticles, i.e., nanofluids. There are differences between various combinations of base fluids and nanoparticles prepared in different ways. The main goal of this review was to present recent research in this field sorted by the used nanoparticles. Nanofluids based on mineral oils, natural, or synthetic esters were investigated in terms of the nature of nanoparticles, particularly Al₂O₃, TiO₂, Fe₂O₃, Fe₃O₄, graphene, fullerene, and others. The combinations of environmentally friendly oils and nanoparticles were presented. Finally, the article focused on the description of current dielectric fluids usable in power transformers and the possibilities of improving new and existing fluids with nanoparticles, especially their physical, dielectric, and chemical properties, but with regard to environmental aspects.

According to the latest research, nanofluids as a possible future substitution for high-voltage equipment insulation have the potential to enhance the heat transfer and insulation properties of their base fluids. Dielectric properties are represented by breakdown strength (AC, DC, lightning) and dielectric performance as a set of quantities including dissipation factor, permittivity, and volume resistivity. In this study, natural and synthetic esters were mixed with C₆₀ nanoparticles. Samples were examined for dissipation factor, relative permittivity, and volume resistivity at temperatures between 25 °C and 140 °C to monitor changes in dielectric performance with rising temperature, in accordance with IEC 60247. In addition, the samples were tested for AC breakdown voltage (using mushroom-like electrodes with a gap distance of 1 mm) and evaluated using the Weibull distribution statistical method. These measurements allowed complex evaluation of the examined mixtures and the determination of optimal concentration for each ester-based nanofluid.

Due to the constant increase in the number of electronic devices, there is a long-term impact of the electromagnetic field (EMF) on human health. In addition, on the other hand, the operation of electronic devices will be affected if the radiation level is too high. Shielding is used to reduce radiation exposure. The aim of this paper is therefore to examine the shielding effectiveness (SE) of concrete depending on the change of its relative permittivity. The paper performs simulations through a waveguide in the Ansys software. The investigated material "concrete" was placed in the middle of a waveguide with a thickness of 10 cm. The frequency range is from 1.6 GHz to 5 GHz. During the experiment, the shielding of wet and dry concrete were determined.

Further research and development in the field of microgrids and related modelling and testing will be necessary for successful application in practice, which will require various model elements. It will be possible to create near-real test microgrids to help better understand the behaviour of such grids. For this reason, it is necessary to develop elements of independent parts that appear in distribution networks that will experience conversion to microgrids in the future. Therefore, this article will describe and propose models of basic protection relays, whose potential for application in microgrids is high. The article will additionally provide models of some power supplies that will be found in such reconstructed new grids.