Investigating High Intensity Thermal Faults in Ester-Based Transformer Oil: A Dissolved Gas Analysis Approach
Received: 22 September 2025 | Revised: 3 November 2025 | Accepted: 9 November 2025 | Online: 12 December 2025
Corresponding author: Manjusha S. Nambiar
Abstract
Dissolved Gas Analysis (DGA) is a significant diagnostic tool for assessing transformer conditions, especially for detecting thermal faults. These faults, stemming from heightened thermal and electrical stresses on liquid insulation and cellulosic materials, generate various gases dissolved in oil. With the rise of environmental concerns, ester-based liquid insulation, like natural and synthetic esters, is an alternative to Mineral Oil (MO) in transformers. However, interpreting DGA data for ester-based oils requires an understanding of the distinct fault gas profiles they exhibit. In the current study, high intensity thermal faults were generated and analyzed by DGA in three different types of transformer oils: MO, natural ester, and synthetic ester, utilizing a novel method of inducing/which induces high intensity thermal stress. The results revealed differences in fault gas generation and concentrations among the three oil types, highlighting the importance of tailored interpretation methods. Since standard DGA interpretation methods are not available for ester filled transformers, these results were validated using established DGA interpretation techniques of MOs. While traditional methods may not fully capture fault conditions in natural and synthetic esters, the present study proposes Duval Triangles and Pentagons for accurate interpretation, shedding light on fault types and their implications for transformer health. The critical role of DGA in assessing transformer health is underscored, particularly in the context of evolving insulation technologies towards a greener future.
Keywords:
Dissolved Gas Analysis (DGA), thermal fault, natural ester, synthetic ester, interpretation techniques, duval triangles and pentagonsDownloads
References
Y. Shirasaka, H. Murase, S. Okabe, and H. Okubo, "Cross-sectional comparison of insulation degradation mechanisms and lifetime evaluation of power transmission equipment," IEEE Transactions on Dielectrics and Electrical Insulation, vol. 16, no. 2, pp. 560–573, Apr. 2009. DOI: https://doi.org/10.1109/TDEI.2009.4815192
J. S. N’cho, I. Fofana, Y. Hadjadj, and A. Beroual, "Review of Physicochemical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers," Energies, vol. 9, no. 5, May 2016, Art. no. 367. DOI: https://doi.org/10.3390/en9050367
M. Rafiq, M. Shafique, A. Azam, M. Ateeq, I. A. Khan, and A. Hussain, "Sustainable, Renewable and Environmental-Friendly Insulation Systems for High Voltages Applications," Molecules, vol. 25, no. 17, Jan. 2020, Art. no. 3901. DOI: https://doi.org/10.3390/molecules25173901
C. Li et al., "Experimental study of ignition process caused by poor electrical contact of connecter," Process Safety and Environmental Protection, vol. 189, pp. 1517–1526, Sept. 2024. DOI: https://doi.org/10.1016/j.psep.2024.07.006
V. Babrauskas, "Electrical Fires," in SFPE Handbook of Fire Protection Engineering, M. J. Hurley, D. Gottuk, J. R. Hall, K. Harada, E. Kuligowski, M. Puchovsky, J. Torero, J. M. Watts, and C. Wieczorek, Eds. New York: Springer, 2016, pp. 662–704. DOI: https://doi.org/10.1007/978-1-4939-2565-0_22
C. Aj, M. A. Salam, Q. M. Rahman, F. Wen, S. P. Ang, and W. Voon, "Causes of transformer failures and diagnostic methods – A review," Renewable and Sustainable Energy Reviews, vol. 82, pp. 1442–1456, Feb. 2018. DOI: https://doi.org/10.1016/j.rser.2017.05.165
S. Tenbohlen, S. Coenen, M. Djamali, A. Müller, M. H. Samimi, and M. Siegel, "Diagnostic Measurements for Power Transformers," Energies, vol. 9, no. 5, May 2016, Art. no. 347. DOI: https://doi.org/10.3390/en9050347
J. Faiz and R. Heydarabadi, "Diagnosing power transformers faults," Russian Electrical Engineering, vol. 85, no. 12, pp. 785–793, Dec. 2014. DOI: https://doi.org/10.3103/S1068371214120207
S. Kim, H. Seo, and J. Jung, "Advanced dissolved gas analysis method with stray gassing diagnosis," in 2016 International Conference on Condition Monitoring and Diagnosis, Xi’an, China, Sept. 2016, pp. 522–525. DOI: https://doi.org/10.1109/CMD.2016.7757877
J. Torres, J. M. Guerrero, W. Leones, and C. A. Platero, "Implementation of a Condition Monitoring Software for Mineral Oil-Immersed Transformers via Dissolved Gas In-Oil Analysis," in 2021 IEEE International Conference on Environment and Electrical Engineering and 2021 IEEE Industrial and Commercial Power Systems Europe, Bari, Italy, Sept. 2021, pp. 1–6. DOI: https://doi.org/10.1109/EEEIC/ICPSEurope51590.2021.9584615
S. Singh and M. N. Bandyopadhyay, "Dissolved gas analysis technique for incipient fault diagnosis in power transformers: A bibliographic survey," IEEE Electrical Insulation Magazine, vol. 26, no. 6, pp. 41–46, Nov. 2010. DOI: https://doi.org/10.1109/MEI.2010.5599978
J. Dai, H. Song, G. Sheng, and X. Jiang, "Dissolved gas analysis of insulating oil for power transformer fault diagnosis with deep belief network," IEEE Transactions on Dielectrics and Electrical Insulation, vol. 24, no. 5, pp. 2828–2835, Oct. 2017. DOI: https://doi.org/10.1109/TDEI.2017.006727
C57.104-2019 - IEEE Guide for the Interpretation of Gases Generated in Mineral Oil-Immersed Transformers. IEEE, 2019.
C. Xiang, Q. Zhou, J. Li, Q. Huang, H. Song, and Z. Zhang, "Comparison of Dissolved Gases in Mineral and Vegetable Insulating Oils under Typical Electrical and Thermal Faults," Energies, vol. 9, no. 5, May 2016, Art. no. 312. DOI: https://doi.org/10.3390/en9050312
M. Danikas and R. Sarathi, "Alternative Fluids – with a Particular Emphasis on Vegetable Oils – as Replacements of Transformer Oil: A Concise Review," Engineering, Technology & Applied Science Research, vol. 10, no. 6, pp. 6570–6577, Dec. 2020. DOI: https://doi.org/10.48084/etasr.3943
D. Hanson et al., "Understanding dissolved gas analysis of ester liquids: An updated review of gas generated in ester liquid by stray gassing, thermal decomposition and electrical discharge," in 2016 IEEE Electrical Insulation Conference, Montreal, QC, Canada, June 2016, pp. 138–144. DOI: https://doi.org/10.1109/EIC.2016.7548611
K. N. Koutras, I. A. Naxakis, A. E. Antonelou, V. P. Charalampakos, E. C. Pyrgioti, and S. N. Yannopoulos, "Dielectric strength and stability of natural ester oil based TiO2 nanofluids," Journal of Molecular Liquids, vol. 316, Oct. 2020, Art. no. 113901. DOI: https://doi.org/10.1016/j.molliq.2020.113901
A. J. Amalanathan, R. Sarathi, S. Prakash, A. K. Mishra, R. Gautam, and R. Vinu, "Investigation on thermally aged natural ester oil for real-time monitoring and analysis of transformer insulation," High Voltage, vol. 5, no. 2, pp. 209–217, 2020. DOI: https://doi.org/10.1049/hve.2019.0178
IEC 60599:2022 - Mineral oil-filled electrical equipment in service - Guidance on the interpretation of dissolved and free gases analysis. Switzerland: IEC, 2022.
E. Dörnenburg and W. Strittmatter, "Monitoring oil-cooled transformers by gas-analysis," Brown Boveri Review, vol. 61, pp. 238–247, 1974.
M. Duval and L. Lamarre, "The new Duval Pentagons available for DGA diagnosis in transformers filled with mineral and ester oils," in 2017 IEEE Electrical Insulation Conference, Baltimore, MD, USA, June 2017, pp. 279–281. DOI: https://doi.org/10.1109/EIC.2017.8004683
M. Duval and L. Lamarre, "The duval pentagon-a new complementary tool for the interpretation of dissolved gas analysis in transformers," IEEE Electrical Insulation Magazine, vol. 30, no. 6, pp. 9–12, Nov. 2014. DOI: https://doi.org/10.1109/MEI.2014.6943428
Downloads
How to Cite
License
Copyright (c) 2025 Manjusha S. Nambiar, C. N. Murthy, Nitin Shingne
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors who publish with this journal agree to the following terms:
- Authors retain the copyright and grant the journal the right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) after its publication in ETASR with an acknowledgement of its initial publication in this journal.
