Abstract:The paper is focused on the possibility of replacing petroleum-based oils used as electro-insulating fluids in high voltage machinery. Based on ten years of study the candidate base oil for the central European region is rapeseed (Brassica napus) oil. Numerous studies on the elementary properties of pure natural esters have been published. An advantage of natural ester use is its easy biodegradability, tested according to OECD-301D (Organisation for Economic Co-operation and Development) standard, and compliance with sustainable development visions. A rapeseed oil base has been chosen for its better resistance to degradation in electric fields and its higher oxidation stability. The overall ester properties are not fully competitive with petroleum-based oils and therefore have to be improved. Percolation treatment and oxidation inhibition by a phenolic-type inhibitor is proposed and the resulting final properties are discussed. These resulting fluid properties are further improved using titanium dioxide (TiO 2 ) nanoparticles with a silica surface treatment. This fluid has properties suitable for use in sealed distribution transformers with the advantage of a lower price in comparison with other currently used biodegradable fluids.
Interesting electrical properties represent the epoxy nanocomposites, because the addition of nanofillers to a pure epoxy resin demonstrate several advantages opposite to pure epoxy resin without nanofillers. In the last 20 years, the dielectric properties (the complex permittivity and dissipation factor) of epoxy nanocomposites had been evaluated and the results clearly show that they are lower than that of base epoxy and microcomposites when insulating oxides were used as the fillers. Nowadays the epoxy and epoxy based composites are preferred insulating materials for many electrical applications. The influence of the various concentrations of ZnO nanoparticles in epoxy resin Vukol 022 on the changes of the complex permittivity and dissipation factor has been measured at the temperature range from 20 °C to 120 °C by a capacitance method in the frequency ranges from 1 mHz to 1 MHz. In this contribution, we present a study of the influence of 1,0 wt.% and 5,0 wt. % concentrations of ZnO nanofillers on the dielectric properties of the epoxy resin. From the frequency dependence of dissipation factor, α-relaxation process and its shift to lower frequencies with ZnO fillers were observed.
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