Oil Immersed Distribution Transformer HST Reduction using Vegetable Oils and ONAN Cooling

Document Type : Research Paper


Department of Engineering, Imam Khomeini International University, Qazvin, Iran


Today, the use of electricity sources is increasing as cities are growing. With the increasing use of mineral oils for transformers cooling in the distribution network, due to the problems encountered using these oils, an alternative fluid should be used inside the transformers instead of mineral oils. Therefore, mineral oils should be replaced with fluids that are more compatible with nature due to the environmental hazards and high costs. Hence, vegetable oils can be used as suitable alternatives for the mineral oils in transformers due to their low risk and the renewability. On the other hand, compared to the mineral oils that have a fire point of about 151 Celsius degrees, vegetable oils have fire points higher than 311 Celsius degrees. As a result, from this viewpoint, they are considered as harmless fluids. Vegetable oils are simply degraded in the nature, and due to their different chemical structures compared to the mineral oils, they can increase the life of the equipment. Besides, the most important point is that they improve the transformer cooling performance, in terms of thermal analysis. Thus, in this paper, the distribution transformer electromagnetic-thermal analysis and conjugate heat transfer, in presence of different types of vegetable oils, and different types of cores such as grain-oriented silicon steel, amorphous and vitroperm alloy are investigated. Afterwards, the obtained results, especially hot spot temperature, are compared with distribution transformer containing mineral oil. ANSYS software has also been used for simulations.


Main Subjects

Publisher’s Note Shahid Chamran University of Ahvaz remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

[1] Rajab, A., Sulaeman, A., Sudirham, S., Suwarno, S., A comparison of dielectric properties of palm oil with mineral and synthetic types insulating liquid under temperature variation, Journal of Engineering and Technological Sciences, 43(3), 2001, 191-208.
[2]  McShane, C.P., Relative properties of the new combustion-resist vegetable-oil-based dielectric coolants for distribution and power transformers, IEEE Transactions on Industry Applications, 37(4), 2001, 1132–1139.
[3] Bashi, S.M., Abdullahi, U.U., Yunus, R., Nordin, A., Use of natural vegetable oils as alternative dielectric transformer coolants, Journal - The Institution of Engineers, Malaysia, 67(2), 2006, 4-9.
[4] Dasgupta, I., Design of transformers, McGraw-Hill, 2002.
[5] Kulkarni, S.V., Khaparde, S.A., Transformer Engineering; Design and Practice, CRC Press, 2004.
[6] IEC 60076-7, Power Transformers-Part 7: loading guide for oil-immersed power transformers, 2005.
[7] Fernández, I., Ortiz, A., Delgado, F., Renedo, C., Perez, S., Comparative evaluation of alternative fluids for power transformers, Electric Power Systems Research, 98, 2013, 58-69.
[8] Rafiq, M., Lv, Y.Z., Zhou, Y., Ma, K.B., Wang, W., Li, C.R., Wang, Q., Use of vegetable oils as transformer oils – a review, Renewable and Sustainable Energy Reviews, 52, 2015, 308-324.
[9] Martin, D., Wang, Z.D., Statistical analysis of the AC breakdown voltages of ester based transformer oils, IEEE Transactions on Dielectrics and Electrical Insulation, 15(4), 2008, 1044-1050.
[10] Tenbohlen, S., Koch, M., Aging performance and moisture solubility of vegetable oils for power transformers, IEEE Transactions on Power Delivery, 25(2), 2010, 825-830.
[11] Oommen, T.V., Vegetable oils for liquid-filled transformers, IEEE Electrical Insulation Magazine, 18(1), 2002, 6-11.
[12] Martin, D., Saha, T., Mcpherson, L., Condition monitoring of vegetable oil insulation in in-service power transformers: some data spanning 10 years, IEEE Electrical Insulation Magazine, 33(2), 2017, 44-51.
[13] Feil, D.L.P, Silva, P.R., Bernardon, D.P., Marchesan, T.B., Sperandio, M., Medeiros, L.H., Development of an efficient distribution transformer using amorphous core and vegetable insulating oil, Electric Power Systems Research, 144, 2017, 268-279.
[14] Zhang, J., Li, X., Oil cooling for disk-type transformer windings—Part II: parametric studies of design parameters, IEEE Transactions on Power delivery, 21(3), 2006, 1326-1332.
[15] Rahimpour, E., Barati, M., Schäfer, M., An investigation of parameters affecting the temperature rise in windings with zigzag cooling flow path, Applied Thermal Engineering, 27, 2007, 1923-1930.
[16] Taghikhani, M.A., Gholami, A., Estimation of hottest spot temperature in power transformer windings with NDOF and DOF cooling, Scientia Iranica, Transactions D: Computer Science & Engineering and Electrical Engineering, 16(2), 2009, 163-170.
[17] Torriano, F., Chaaban, M., Picher, P., Numerical study of parameters affecting the temperature distribution in a disc-type transformer winding, Applied Thermal Engineering, 30, 2010, 2034-2044.
[18] Taghikhani, M.A., Modeling of heat transfer in layer-type power transformer, Przeglad Elektrotechniczny, 87(12), 2011, 121-123.
[19] Skillen, A., Revell, A., Iacovides, H., Wu, W., Numerical prediction of local hot-spot phenomena in transformer windings, Applied Thermal Engineering, 36, 2012, 96-105.
[20] Coddé, J., Veken, W.V.D, Baelmans, M., Assessment of a hydraulic network model for zig-zag cooled power transformer windings, Applied Thermal Engineering, 80, 2015, 220-228.
[21] Liu, C., Ruan, J., Wen, W., Gong, R., Liao, C., Temperature rise of a dry-type transformer with quasi-3D coupled-field method, IET Electric Power Applications, 10(7), 2016, 598–603.
[22] Silva, J.R.D., Bastos, J.P.A., On-line evaluation of power transformer temperatures using magnetic and thermodynamics numerical modeling, IEEE Transactions on Magnetics, 53(6), 2017, 8106104.
[23] Das, A.K., Chatterjee, S., Finite element method-based modelling of flow rate and temperature distribution in an oil-filled disc-type winding transformer using COMSOL multiphysics, IET Electric Power Applications, 11(4), 2017, 664–673.
[24] Garelli, L., Ríos Rodriguez, G.A., Kubiczek, K., Lasek, P., Stepien, M., Smolka, J., Storti, M.,  Pessolani, F., Amadei, M., Thermo-magnetic-fluid dynamics analysis of an ONAN distribution transformer cooled with mineral oil and biodegradable esters, Thermal Science and Engineering Progress, 23, 2021, 100861.
[25] de  Melo, A.S., Calil, W.V., Salazar, P.D.P., Liboni, L.H.B., Costa, E.C.M., Flauzino, R.A., Applied methodology for temperature numerical evaluation on high current leads in power transformers, International Journal of Electrical Power and Energy Systems , 131, 2021, 107014.
[26] Herrera, S., Bonkers about biofuels, Nature Biotechnology, 24, 2006, 755-760.
[27] Qiu, F., Li, Y., Yang, D., Li, X., Sun, P., Biodiesel production from mixed soybean oil and rapeseed oil, Applied Energy, 88(6), 2011, 2050-2055.
[28] Sitorus, H.B.H., Beroual, A., Setiabudy, R., Bismo, S., Pre-breakdown phenomena in new vegetable oil-based Jatropha Curcas seeds as substitute of mineral oil in high voltage equipment, IEEE Transactions on Dielectrics and Electrical Insulation, 22(5), 2015, 2442-2448.
[29] Mariprasath, T., Kirubakaran, V., A critical review on the characteristics of alternating liquid dielectrics and feasibility study on pongamia pinnata oil as liquid dielectrics, Renewable and Sustainable Energy Reviews, 65, 2016, 784-799.
[30] Raeisian, L., Niazmand, H., Ebrahimnia-Bajestan, E., Werle, P., Feasibility study of waste vegetable oil as an alternative cooling medium in transformers, Applied Thermal Engineering, 151, 2019, 308-317.
[31] Usman, M.A., Olanipekun, O.O., Henshaw, U.T., A comparative study of soya bean oil and palm kernel oil as alternatives to transformer oil, Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS), 3(1), 2012, 33-37.
[32] Taghikhani, M.A., Afshar, M.R., Fans arrangement analysis in oil forced air natural cooling method of power transformer radiator, Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 235(4), 2021, 904-913.
[33] Taghikhani, Z., Taghikhani, M.A., Gharehpetian, G.B., Mineral oil based CuO nanofluid-immersed transformers analysis concerning the efficacy of nanocrystalline alloy core in reduction of losses and HST, Journal of Magnetism and Magnetic Materials, 537, 2021, 168184.
[34] Stebel, M., Kubiczek, K., Rodriguez, G.R., Palacz, M., Garelli, L., Melka, B., Haida, M., Bodys, J., Nowak, A.J, Lasek, P., Stepien, M., Pessolani, F., Amadei, M., Granata, D., Storti, M., Smolka, J., Thermal analysis of 8.5 MVA disk-type power transformer cooled by biodegradable ester oil working in ONAN mode by using advanced EMAG–CFD–CFD coupling, International Journal of Electrical Power and Energy Systems, 136, 2022, 107737.
[35] Smolka, J., Nowak, A.J., Experimental validation of the coupled fluid flow, heat transfer and electromagnetic numerical model of the medium-power dry-type electrical transformer, International Journal of Thermal Sciences, 47(10), 2008, 1393-1410
[36] Heidary, A., Taghikhani, M.A., Electromagnetic-mechanical-thermal amorphous core transformer simulation compare to conventional transformers using FEM, Modares Mechanical Engineering, 18(3), 2018, 95-106. (in Persian)
[37] Paramane, B., Veken, W.V.D., Sharma, A., A coupled internal–external flow and conjugate heat transfer simulations and experiments on radiators of a transformer, Applied Thermal Engineering, 103, 2016, 961-970.