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Comparative study of dielectric properties of mineral oil, synthetic ester and natural ester
*Miloš Šárpataky
Department of Electric Power Engineering, Faculty of Electrical Engineering and Informatics, Technical University of Košice
Juraj Kurimský
Department of Electric Power Engineering, Faculty of Electrical Engineering and Informatics, Technical University of Košice
Michal Rajňák
Slovak Academy of Sciences
Michal Krbal
Department of Electrical Power Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology
Luděk Pelikán
Department of Electrical Power Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology
Last modified:
2022-06-20
Abstract
The current research of insulating oils for high-voltage applications focuses mainly on biodegradable oils that are in line with sustainable development. Mineral oils may in the future be replaced by more environmentally friendly materials with similar properties. One of the probable options as substitutes in the future will be synthetic or natural esters. This paper presents a comparative experimental study of mineral oil, natural ester, and synthetic ester and their dielectric properties, specifically AC breakdown voltage, lightning breakdown voltage, and thermal dependence of dissipation factor, volume resistivity, and permittivity. Measurements of AC and lightning breakdown voltage were performed according to IEC 60156 with a horizontally positioned sphere–sphere electrode system. Synthetic ester reached the mean value of AC breakdown voltage 60.2 kV, lightning breakdown voltage with positive polarity 144.3 kV, and with negative polarity 148.6 kV. Natural ester showed a mean value of AC breakdown voltage 58.4 kV, the lightning breakdown voltage of positive and negative polarity was 149.5 kV and 151.5 kV, respectively. Measurement of dissipation factor, volume resistivity, and permittivity was executed in accordance with IEC 60247 2004. The dissipation factor moved from 0.0031 at 20°C to 0.3119 at 140°C for synthetic ester and from 0.0011 at 20°C to 0.0331 at 140°C for natural ester. These results are compared with the dielectric properties of mineral oil. The challenging problem of potential oil substitution in power transformers is discussed.
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