Thermal stress analysis of dry-type transformers under short-circuit conditions considering temperature-dependent epoxy properties
46 viewsDOI:
https://doi.org/10.54939/1859-1043.j.mst.113.2026.20-29Keywords:
Dry-type transformer; Amorphous core; Temperature-dependent properties; Thermo-mechanical stress.Abstract
Accurate prediction of temperature rise and hotspot formation is critical for the lifetime and safety of cast-resin dry-type transformers. Conventional thermal design methods typically assume constant thermophysical properties for epoxy insulation, neglecting their nonlinear temperature dependence - an oversimplification that can introduce significant errors under severe operating conditions such as short-circuit faults. This study applies a temperature-dependent thermal modeling approach to a 320 kVA, 22/0.4 kV amorphous-core dry-type transformer, employing coupled Finite Element Method (FEM) and Computational Fluid Dynamics (CFD) to simulate the three-dimensional transient temperature field with temperature-dependent thermal conductivity, diffusivity, and specific heat capacity of epoxy insulation. Results show that the high-voltage winding is the most thermally critical region under short-circuit conditions, and that incorporating temperature-dependent material properties yields higher predicted hotspot temperatures and stronger thermal stress concentration compared to conventional constant-property assumptions. These findings highlight the importance of temperature-dependent modeling in transformer thermal design and provide a more reliable basis for structural optimization and safety assessment.
References
[1]. Bonneville Power Administration, "Dry-type transformer new construction and retrofit energy savings potential," BPA, (2021).
[2]. P. Kumar and P. Verma, "Review paper on diagnostics study of dry transformer," CEUR Workshop Proc., vol. 3058, pp. 1–3, (2021).
[3]. B. Doan Thanh, "Determination of winding destroy limit area for a power series of amorphous core transformers," J. Mil. Sci. Technol., vol. 103, no. 103, pp. 11–21, (2025). DOI: 10.54939/1859-1043.j.mst.103.2025.11-21 DOI: https://doi.org/10.54939/1859-1043.j.mst.103.2025.11-21
[4]. D. S. He et al., "Simulation and experimental analysis of dynamic thermal rise relaxation characteristics for dry-type distribution transformer," Int. J. Emerging Electric Power Syst., vol. 26, no. 2, pp. 419–435, (2025). DOI: 10.1515/ijeeps-2024-0106 DOI: https://doi.org/10.1515/ijeeps-2024-0106
[5]. Z. Guan et al., "Research on the thermal aging characteristics of epoxy resin for high frequency transformers based on activation energy," in Proc. IEEE Int. Conf. Electrical Materials and Power Equipment (ICEMPE), Harbin, China, pp. 1–5, (2025). DOI: 10.1109/ICEMPE66159.2025.11122976 DOI: https://doi.org/10.1109/ICEMPE66159.2025.11122976
[6]. B. D. Thanh, T. H. Le, and V. D. Quoc, "A comparative analysis of axial and radial forces in windings of amorphous core transformers," Int. J. Electr. Eng. Educ., (2024). DOI: 10.5829/ije.2024.37.01a.18 DOI: https://doi.org/10.5829/IJE.2024.37.01A.18
[7]. B. D. Thanh, D. D. Tung, and T.-H. Le, "Computation of electromagnetic forces in the windings of amorphous core transformers," Arch. Electr. Eng., (2023). DOI: 10.24425/aee.2023.145423 DOI: https://doi.org/10.24425/aee.2023.145423
[8]. Y. Sun et al., "Hotspot temperature prediction of dry-type transformers based on particle filter optimization with support vector regression," Symmetry, vol. 13, no. 8, p. 1320, (2021). DOI: 10.3390/sym13081308 DOI: https://doi.org/10.3390/sym13081320
[9]. Y. Wang, C. Feng, R. Fei, and Y. Luo, "Thermal-ageing characteristics of dry-type transformer epoxy composite insulation," High Performance Polym., vol. 32, no. 7, pp. 741–752, (2020). DOI: 10.1177/0954008320906439 DOI: https://doi.org/10.1177/0954008320906439
[10]. B. T. Doan, "Calculation of temperature distribution of air-cooled three-phase dry transformer," J. Sci. Technol. – Univ. Danang, vol. 20, no. 11.2, pp. 38–43, (2022).
[11]. P. H. Hai et al., "Calculation of electromagnetic force and temperature distribution of amorphous transformers in different operating modes by finite element method," CTU J. Innovation Sustainable Dev., vol. 16, no. 1, pp. 66–75, (2024). DOI: 10.22144/ctujsd.2024.269 DOI: https://doi.org/10.22144/ctujoisd.2024.269
[12]. K. Dawood and S. Kul, "Influence of core window height on thermal characteristics of dry-type transformers," Case Stud. Therm. Eng., (2025). DOI: 10.1016/j.csite.2025.105746 DOI: https://doi.org/10.1016/j.csite.2025.105746
[13]. M. S. Seddik, J. Shazly, and M. B. Eteiba, "Thermal analysis of power transformer using 2D and 3D finite element method," Energies, vol. 17, no. 13, p. 3203, (2024). DOI: 10.3390/en17133203 DOI: https://doi.org/10.3390/en17133203
[14]. J. P. Américo, J. V. Leite, and C. F. Mazzola, "Enhanced thermal modeling of three-phase dry-type transformers," Case Stud. Therm. Eng., vol. 58, p. 104445, (2024). DOI: 10.1016/j.csite.2024.104445 DOI: https://doi.org/10.1016/j.csite.2024.104445
[15]. D. S. He, Z. D. Jia, J. X. Wang, J. B. Fu, F. He, and F. Dai, "Investigating temperature rise dynamics at hot-spots within dry-type transformer windings: A comparative analysis across varied loading rates and an extrapolative computational model," Case Stud. Therm. Eng., vol. 60, p. 104699, (2024). DOI: 10.1016/j.csite.2024.104699 DOI: https://doi.org/10.1016/j.csite.2024.104699
[16]. M. De Melo Antunes et al., "Estimation of effective temperature-dependent thermal properties of glass fiber-reinforced polymer for air-core reactor insulation: A case study using an alternative inverse approach," Int. J. Thermophysics, vol. 45, no. 12, (2024). DOI: 10.1007/s10765-024-03468-3 DOI: https://doi.org/10.1007/s10765-024-03468-3
[17]. P. H. Hai et al., "A study on thermal properties of epoxy materials in a dry-type transformer," J. Sci. Technol. – Univ. Danang, vol. 19, no. 7, pp. 29–34, (2021).
[18]. P. H. Hai and L. D. Tung, "Study on the thermal distribution of dry-type transformer with epoxy-cast windings at rated load and partial load," J. Meas., Control Autom., vol. 28, no. 3, pp. 47–52, (2024).
[19]. H. H. Pham, "Nghiên cứu lực ngắn mạch tổng hợp có tính đến ảnh hưởng phân bố nhiệt trong máy biến áp khô có lõi thép vô định hình," Thesis, Hanoi University of Science and Technology, Hanoi, Vietnam, (2021) (in Vietnamese).
