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 (TiO2) 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.
Highlights
When designing a modern electrical machine, the technical aspects of the matter are not the only important ones—the environmental compatibility of the materials has become more important.Natural ester fluids have potential for industrial usage due to their good biodegradability
This environmental property is an advantage in some technical solutions where devices require a liquid medium for their operation and where there is a potential risk of soil contamination in the event of leakage [2]
This liquid is expected to be competitive in its price and overall properties to the mineral-typically based electroinsulating liquids used in medium voltage transformers
Summary
When designing a modern electrical machine, the technical aspects of the matter are not the only important ones—the environmental compatibility of the materials has become more important. A good biodegradable substance according to the standard is a substance which in the case of the contamination of soil, is naturally degraded by at least seventy percent by the soil bacteria in 28 days This environmental property is an advantage in some technical solutions where devices require a liquid medium (for example, for cooling or to create a potential barrier to an electric field) for their operation and where there is a potential risk of soil contamination in the event of leakage [2]. They can be produced with a competitive final price from local natural sources These facts are the basic idea behind the preparation of a new electro-insulating liquid based on rapeseed oil. The lower of measured characteristics for each insulation system used, as the slope value serves as measured statistical thethe experimental results of the electric stress test.
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