Study of the presence of pro-oxidative properties in phenolic oxidation inhibitors in relation to modern transformer oils

ACTUALITY. In the community of Russian specialists servicing oil-filled transformers, there is an established opinion that when the concentration of the phenolic oxidation inhibitor Ionol (DBPC) in the oil drops below 0.1% (wt.), the transformer oil begins to oxidize faster than in the absence of Ionol. This is the so-called “pro-oxidizing effect” described in 1968. Modern hydrocracking transformer oils differ significantly from the former oils in terms of hydrocarbon composition, but the opinion about the pro-oxidizing properties of Ionol remains, despite the lack of such information in foreign studies. OBJECTIVE. To reveal the presence or absence of pro-oxidative action of phenolic antioxidants, Ionol and 2,6-DTBP, when their concentration in transformer oil is reduced. METHODS. Two series of oil samples were prepared for the study: with Ionol and 2,6-DTBP additive. The concentration of additives: 0; 0.05; 0.1 and 0.2 % (wt.). VG grade oil produced by hydrocracking technology was used as a base mineral oil. All oils were subjected to accelerated thermal degradation at elevated temperature. Destructive changes in the hydrocarbon base of oils were analyzed by IR absorption spectra. Changes in the relative content of degradation products dissolved in the oil were analyzed using UV-visible absorption spectra. RESULTS. On the basis of the analysis of optical spectra of both series of oils, it was obtained that as the initial concentration of any of the phenolic oxidation inhibitors in the oil decreases, the intensity of thermodestructive changes in the hydrocarbon composition of the oils consistently increases. It is shown that in transformer oils produced by hydrocracking technology both additives in the concentration range of 0.05÷0.1 % do not show pro-oxidizing properties. It is concluded that the widespread idea about pro-oxidizing effect of Ionol at its concentration in transformer oil less than 0.1 % should be considered as not corresponding to reality.

1. Lukenda N. Not all mineral oils are equal. Transformers Magazine. 2019. 6(4):112-117.

2. MIDEL 7131 - premium performance since the 1970s. – URL: https://www.midel.com/midelrange/midel-7131/ (дата обращения: 01.09.2024)

3. Rozga P., Beroual A, Przybylek P., Jaroszewski M. et al. A Review on Synthetic Ester Liquids for Transformer Applications. Energies. 2020; 13(23):6429. https://doi.org/10.3390/en13236429

4. Rapeseed natural ester dielectric fluid. – URL: https://www.cargill.com/bioindustrial/dielectricfluids/fr3r-fluid (дата обращения: 01.09.2024).

5. Rao U.M., Fofana I., N’cho J.S. On Some Imperative IEEE Standards for Usage of Natural Ester Liquids in Transformers. IEEE Access. 2020;8:145446-145456. doi: 10.1109/ACCESS.2020.3014600.

6. Shen Z., Wang F., Wang Z., Li J. A critical review of plant-based insulating fluids for transformer: 30-year development. Renewable and Sustainable Energy Reviews. 2021;141. 110783. https://doi.org/10.1016/j.rser.2021.110783

7. Transformer oils market. Analytical review. URL: https://www.marketsandmarkets.com/Market Reports/transformer-oil-market-967.html/ (дата обращения: 01.09.2024

8. Lyutikova M.N., Korobeynikov S.M., Rao U.M. Fofana I. Mixed Insulating Liquids With Mineral Oil for High-Voltage Transformer Applications: A Review. IEEE Transactions on Dielectrics and Electrical Insulation. 2022;29(2):454-461. doi: 10.1109/TDEI.2022.3157908.

9. Lyutikova M., Korobeynikov S., Konovalov A. Evaluation of the Properties of Mixtures of Aromatic Mineral Oil and Synthetic Ester for High-Voltage Equipment. IEEE Transactions on Dielectrics and Electrical Insulation. 2021; 28(4):1282-1290. doi: 10.1109/TDEI.2021.009636

10. Rouabeh J., M’barki L., Hammami A., et. al. Studies of different types of insulating oils and their mixtures as an alternative to mineral oil for cooling power transformers. Heliyon. 2019;5(3). doi: 10.1016/j.heliyon.2019.e01159.

11. Hao J., Zhang J., Ye W., et. al. Development of Mixed Insulation Oil as Alternative Liquid Dielectric: A Review. CSEE Journal of Power and Energy Systems. 2024; 10(3):1242-1258. doi: 10.17775/CSEEJPES.2023.05960

12. Lipshtein R.A., Shakhnovich M.I. Transformatornoe maslo. Moscow: Ehnergoatomizdat, 1983. (In Russ).

13. Roginskii V.A. Fenol'nye antioksidanty: Reaktsionnaya sposobnost' i effektivnost'. – Moscow: Nauka; 1988. (In Russ).

14. Lipshtein R.A. O mekhanizme deistviya ingibitorov okisleniya. Prisadki k maslam: Trudy Vtorogo Vsesoyuznogo nauch.-tekhn. soveshchaniya. Moscow: Khimiya Publ., 1968. 169-177. (In Russ).

15. S.P. Vysogorets, “Improvement of the methodology of physical and chemical diagnostics of oil filled transformer equipment”: D. thesis for the degree of Doctor of Technical Sciences. 05.14.12, St. Petersburg, 2020. 423 p.

16. Lizunov SD, Lokhanin AK, editors. Silovye transformatory. Spravochnaya kniga. Moscow: Energoatomizdat; 2004. (In Russ).

17. Atanasova-Höhlein I. IEC 60296 (Ed. 5) – a standard for classification of mineral insulating oil on performance and not on the origin. Transformers magazine. 2021; 8(1):86-91.

18. Turanov A.N. Analiz metodov diagnostiki doli aromaticheskikh grupp v sostave transformatornykh masel. Elektrichestvo. 2022; 4: 72-77. (In Russ).

19. N’cho J.S., Fofana I., Hadjadj Y., et al. Review of Physicochemical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers. Energies. 2016;9(5):367. doi: https://doi.org/10.3390/en9050367

20. Emanuel' N.M., Denisov E.T., Maizus Z.K. Tsepnye reaktsii okisleniya uglevodorodov v zhidkoi faze. M.: Nauka; 1965. (In Russ).

21. Ivanov K.I. Promezhutochnye produkty i promezhutochnye reaktsii avtookisleniya uglevodorodov. M.;-L.: Gostoptekhizdat; 1949. (In Russ).

22. Waters W.A. Mechanism of oxidation of organic compounds. New York: Wiley, 1964. (Russ. ed.: Uoters U.A. Mekhanizm okisleniya organicheskikh soedinenii. Moscow: Mir Publ., 1966; 175 р.)

23. Krishchenko V.P. Blizhnyaya infrakrasnaya spektroskopiya. Moscow: KRONA-PRESS; 1997. (In Russ).

24. Jerry Workman, Jr. The Handbook of Organic Compounds: NIR, IR, Raman, and UV-Vis Spectra Featuring Polymers and Surfactants. 1st ed. Elsevier; 2000.

25. Garifullin M.Sh. Ispol'zovanie metodov opticheskoi spektroskopii dlya diagnostiki mineral'nykh izolyatsionnykh masel. Fundamental'nye issledovaniya. 2013;10: 3299-3304. (In Russ).

26. Garifullin M.Sh., Solobodina Y.N., Bikzinurov A.R., et al. Control of the degradation of the mineral transformer oils hydrocarbon base. E3S Web of Conferences. 2020;216(01055). DOI: https://doi.org/10.1051/e3sconf/202021601055

27. Garifullin M.Sh., Slobodina Y.N., Bikzinurov A.R., et al. Investigation of the content of unsaturated hydrocarbons in transformer oils using IR spectroscopy. Power engineering: research, equipment, technology. 2023;25(5):3-19. (In Russ). doi: https://doi.org/10.30724/1998-9903-2023-25-5-3-19

28. Lyutikova M.N., Nekhoroshev S.V., Kuklina V.M., et al. Identification of Impurities of Unknown Composition in Insulating Oil by Gas Chromatography-Mass Spectrometry (GC-MS). Power Technology and Engineering. 2020;54(4). doi: 10.1007/s10749-020-01257-0.

29. Ågren P., Lillhonga T., Melzer L. Identification and Improved Quantification of Inhibitors in Mineral Insulating Oils using FTIR Spectroscopy and Partial Least Squares Regression: 48 CIGRE Session; 23-28 Aug 2020; Paris, France; 2020. Paper D1-103.

30. Muratova V.M., Nekhoroshev S.V., Gadzhieva A.S., et al. Determination of phenolic-type antioxidant additives in fresh insulating oils by IR spectrometry on a liquid express analysis attachment. Analytics and Control. 2023; 27(2):113-121. (In Russ). doi: 10.15826/analitika.2023.27.2.005

31. Lyutikova M.N., Konovalov A.A., Korobeinikov S.M., et al. Control of the Antioxidant Additive (Ionol) Content in Liquid Insulation of High-Voltage Equipment in Electric Grid Companies Using Modern Instrumental Methods. Power Technology and Engineering. 2019;53(1): 118-125.

32. Garifullin M.Sh., Kozlov V.K. Pribor dlya spektral'nykh issledovanii izolyatsionnykh masel v diapazone 600-1100 nm. Power engineering: research, equipment, technology. 2001; 9-10: 114-116. (In Russ).