Compatibility Testing of New Insulating Fluids and Materials in Distribution Transformer

Pavel Trnka (), Jaroslav Hornak, Magdalena Trnkova, Ondrej Michal, Zdislava Mokra, Pavel Slama, Jiri Kopriva, Pavel Prosr, Jan Leffler and Zdenek Frana
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Pavel Trnka: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Jaroslav Hornak: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Magdalena Trnkova: Independent Researcher, 331 52 Horni Bela, Czech Republic
Ondrej Michal: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Zdislava Mokra: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Pavel Slama: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Jiri Kopriva: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Pavel Prosr: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Jan Leffler: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic
Zdenek Frana: Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 301 00 Pilsen, Czech Republic

Energies, 2025, vol. 18, issue 7, 1-18

Abstract: The introduction of a new insulating oil or, for instance, a new type of insulation or sealing into a transformer necessitates tests for material compatibility. Compatibility tests of liquids with the structural internal materials of transformers are conducted to prevent undesired interactions between insulating fluids and the formation of products that could lead to the generation of undesirable ions, sediments, or chemical compounds that result in a reduction in the dielectric property performance of the fluid. This includes chemical reactions (hydrolysis, hydrogenation, oxidation, formation of sulfates or sulfides, etc.) and degradation, the formation of conductive suspensions, the generation of undesirable condensation, and alterations in other fluid properties, such as interfacial tension between oil and water, viscosity, flashpoint, etc. Changes must also not occur in the strength and hardness of gasket material, which could result in undesirable fluid leakage. This paper describes the novel methodology and results of several proposed tests, including the impact on oil viscosity, material hardness, FT-IR analysis of oils, partial discharges in different oils, dielectric properties, and more, conducted during compatibility and aging tests at 120 °C and 140 °C performed on materials used in particular distribution transformers being prepared for natural ester use. The results show notable differences in the behavior of insulating fluids and aged submerged materials. While mineral oils exhibit lower dissipation factors compared to natural esters, the latter demonstrate slower and less severe hardening effects on gaskets during high-temperature aging (e.g., Shore 35.25 in mineral oil vs. 21–22.5 in natural esters). The tensile strength of the tested cable ties decreased significantly (from 260 to approx. 60 N) in mineral oil but increased in natural ester (320 N/120 °C exposition). This study also highlights a novel insight into partial discharge mechanisms, where differences in viscosity, conductivity phenomena, and dielectric constants result in presented differences in inception voltages and prebreakdown activity.

Keywords: biodegradable fluid; compatibility; insulating liquid; property test; transformer (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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