FEM and CFD analysis of a hybrid cooling system design in oil-type transformers

Year 2022, , 611 - 619, 18.07.2022

Murat Toren

https://doi.org/10.28948/ngumuh.1122317

Abstract

Oil-type transformers (YTT) are electrical machines with high usage in the transmission and distribution process of electrical energy. These transformers are widely used due to their low production costs and wide usage area. In the distribution system of electrical energy, approximately 80-85% of transformers consist of YTT. When these data are taken into account, the importance of the operation, performance parameters and the cooling systems that affect them come to the fore increasingly. The cooling of YTT is generally provided with naphtanic / paraffinic based oils, also called transformer oil. The use of oils for cooling purposes in YTT causes environmental pollution and requires high costs for operation, maintenance-repair activities. Today, current and interdisciplinary researches are carried out for the cooling of transformers with alternative methods. In this study, with a hybrid system, the heat generated during operation at 5kVA YTT is provided to cool the enclosure volume by using water and oil fluids at certain rates. The designed hybrid cooling system is analyzed with the finite element method (FEM) and computational fluid dynamics (CFD), and it is examined from the results that the YTT life cycle can be increased up to 5.48 - 166.6 hours.

Keywords

Oil type Transformer, FEM, CFD, Hybrid Cooling, Life Cycle

Yağlı tip transformatörlerde hibrit bir soğutma sistem tasarımının FEM ve CFD analizleri

Abstract

Yağlı tip transformatörler(YTT), elektrik enerjisinin iletim ve dağıtım sürecinde yüksek kullanıma sahip elektrik makineleridir. Bu transformatörler üretim maliyetlerinin düşük olması ve kullanım alanının geniş olması nedeniyle yaygın olarak kullanılmaktadır. Elektrik enerjisinin dağıtım sistemi içerisinde transformatörlerin yaklaşık % 80-85’i YTT den oluşmaktadır. Bu veriler dikkate alındığında yağlı tip transformatörlerin çalışmaları, performans paramet-releri ve bunları etkileyen soğutma sistemlerinin önemi de artan ölçüde ön plana çıkmaktadır. YTT’nin soğutulması genel olarak trafo yağı da denilen naftanik / parafinik bazlı yağlarla sağlanmaktadır. YTT’de soğutma amaçlı olarak yağların kullanılması, çevre kirliliğine neden olduğu gibi işletme, bakım-onarım faaliyetleri için yüksek maliyet gerektirmektedir. Günümüzde, transformatörlerin alternatif yöntemler ile soğutulması için, güncel ve disiplinler arası araştırmalar yapılmaktadır. Bu çalışmada ise 5kVA YTT’de çalışma sırasında oluşan ısının hibrit bir sistemi ile mahfaza hacminin belirli oranlarda su ve yağ akışkanları kullanılarak soğutulması sağlanmaktadır. Tasarlanan hibrit soğutma sistemi sonlu elemanlar metodu (FEM) ve hesaplamalı akışkanlar dinamiği(CFD) ile analiz edilerek sonuçlardan YTT faydalı ömrünün 5.48 – 166.6 saate kadar arttırılabileceği incelenmektedir.

Keywords

Yağlı tip Transformatör, FEM, CFD, Hibrit soğutma, Faydalı Ömür

References

• I. Iskender, A. Mamizadeh, Nonlinear Thermal Modeling of Indoor and Outdoor Oil – Immersed Power Transformers, J. Electr. Eng., 60, 321–327, 2009.
• D. Aşkın, Kuru Tip Transformatörlerin Sargı Sıcaklık Davranışının Yapay Sinir Ağları Kullanarak Modellenmesi.Yüksek Lisans Tezi, Gazi Üniversitesi, Ankara, Türkiye, 2011.
• E. Rahimpour, D. Azizian, Analysis of temperature distribution in cast-resin dry-type transformers, Electr. Eng.,89, 301–309, 2007. https://doi.org/10.1 007/s00202-006-0008-4.
• X. Huang, L. Zhou, G. Wu, Q. Du, Simulation models of transformer hot-spot temperature, in: Proc. IEEE Int. Conf. Prop. Appl. Dielectr. Mater., 2012. https://doi.org/10.1109/ICPADM.2012.63189 43.
• Y.Z. Lv, Y. Zhou, C.R. Li, Q. Wang, B. Qi, Recent Progress in Nanofluids Based on Transformer Oil: Preparation and Electrical Insulation Properties, 2014. https://doi.org/10.1109/MEI.2014.6882597.
• J. Liu, L. Zhou, G. Wu, Y. Zhao, P. Liu, Q. Peng, Dielectric frequency response of oil-paper composite insulation modified by nanoparticles, IEEE Trans. Dielectr. Electr. Insul.,19, 510–520, 2012. https://doi.org/10.1109/TDEI.2012.6180245.
• G. Yaman, R. Altay, R. Yaman, Validation of computational fluid dynamic analysis of natural convection conditions for a resin dry-type transformer with a cabin, Therm. Sci., 2019. https://doi.org/10.2298/TSCI180919327Y.
• L. Garelli, G.A. Ríos Rodriguez, K. Kubiczek, P. Lasek, M. Stepien, J. Smolka, M. Storti, F. Pessolani, M. Amadei, Thermo-magnetic-fluid dynamics analysis of an ONAN distribution transformer cooled with mineral oil and biodegradable esters, Therm. Sci. Eng. Prog., 23 100861, 2021. https://doi.org/10.1016/J.TSEP.2021. 100861.
• O. Kaymaz, G. Kalkan, A. Erek, Flow and heat transfer characterıstıcs of dıfferent transformer oıls ın one sectıon of transformer radıator, Mühendis ve Makina., 56 , 53–63, 2015.
• R. Liao, J. Hao, L. Yang, S. Liang, J. Yin, Improvement on the anti-aging properties of power transformers by using mixed insulating oil, in: 2010 Int. Conf. High Volt. Eng. Appl. ICHVE 2010, 588–591,2010. https://doi.org/10.1109/ICHVE.2010.56 40772.
• Y. Yuan, R. Liao, A novel nanomodified cellulose insulation paper for power transformer, J. Nanomater,2014. https://doi.org/10.1155/2014/ 510 864.
• T.W. Park, S.H. Han, Numerical analysis of local hot-spot temperatures in transformer windings by using alternative dielectric fluids, Electr. Eng. 97, 261–268, 2015. https://doi.org/10.1007/s00202-015-0335-4.
• T. Committee, IEEE C57.91-1995 Guide for Loading Mineral-Oil- Immersed Transformers, 1995. https://doi.org/10.1109/IEEESTD.1996.7966 5.
• J. Rouabeh, L. M’barki, A. Hammami, I. Jallouli, A. Driss, Studies of different types of insulating oils and their mixtures as an alternative to mineral oil for cooling power transformers, Heliyon., 5 ,e01159, 2019. https://doi.org/10.1016/j.heliyon.2019.e0115 9.
• M. Toren, M. Celebi, Comparative implementation of graphene sheet insulation heat effect in dry-type transformers, Therm. Sci. Eng. Prog., 26,101131, 2021. https://doi.org/10.1016/j.tsep.2021.101131.
• Parts of a Transformer and Basics Explained. http://www.apogeeweb.net/article/1997.html#viii-test-and-transportation-of-the-transfomer, Accessed 27 May 2022.
• F.P. Incropera, D.P. DeWitt, T.L. Bergman, A.S. Lavine, heat and mass transfer - Incropera 6e, Fundam. Heat Mass Transf.,John Wiley and Sons, 2007. https://doi.org/10.1016/j.applthermaleng.20 11.03.022.
• L.W. Pierce, Predicting hottest spot temperatures in ventilated dry type transformer windings, IEEE Trans. Power Deliv., 9, 1160–1172, 1994. https://doi.org/10.1109/61.296303.
• Miyatake Osamu;Fujii Tetsu, Natural Convectıve Heat Transfer Between Vertıcal Parallel Plates Wıth Unequal Heat Fluxes., Heat Transf. - Japanese Res. 3 ,29–33, 1972.
• M. Fujii, S. Gima, T. Tomimura, X. Zhang, Natural convection to air from an array of vertical parallel plates with discrete and protruding heat sources, Int. J. Heat Fluid Flow., 17, 483–490, 1996. https://doi. org/ 10.1016/0142-727X(96)00051-3.