Experimental validation of the coupled fluid flow, heat transfer and electromagnetic numerical model of the medium-power dry-type electrical transformer

This paper presents experimental validation of a numerical model of coupled processes within a three-phase medium-power dry-type electrical transformer. The analysis carried out employed a multi-disciplinary approach involving heat, fluid flow and electromagnetics. The thermal and fluid flow analysis was coupled with an electromagnetic model in order to examine the specific power losses within the coils and the core. The thermal boundary conditions, i.e. the local and temperature-dependent heat fluxes, were computed by considering a numerical model of the surrounding internal and external air. Moreover, separate numerical and analytical models were considered in order to obtain the anisotropic thermal conductivities for different types of coils and also for laminated cores. To validate the numerical model, experimental transformer temperature tests in the short-circuit, open-circuit, and under nominal parameters according to the current European Standards for dry-type transformers were performed. During the tests, temperatures were measured at selected points on elements of the transformer using thermocouples and thermometers, while on the external tank walls an infrared thermography was employed. The obtained numerical results showed that the prediction of the temperature distribution within the analyzed transformers and their surroundings was very accurate.

[1]  E. Snelling.  Soft ferrites: properties and applications , 1969 .

[2]  J. Anderson,et al.  Computational fluid dynamics : the basics with applications , 1995 .

[3]  Amin Behzadmehr,et al.  Low Reynolds number mixed convection in vertical tubes with uniform wall heat flux , 2003 .

[4]  K. Preis,et al.  FEM analysis of eddy current losses in nonlinear laminated iron cores , 2005, IEEE Transactions on Magnetics.

[5]  M. Ozisik.  Heat Transfer: A Basic Approach , 1984 .

[6]  Scott J. Ormiston,et al.  THEORETICAL DETERMINATION OF ANISOTROPIC EFFECTIVE THERMAL CONDUCTIVITY IN TRANSFORMER WINDINGS , 2003 .

[7]  Christophe Le Niliot,et al.  Infrared thermography applied to the resolution of inverse heat conduction problems: recovery of heat line sources and boundary conditions , 1998 .

[8]  Ho-Myung Chang,et al.  Cryogenic cooling system of HTS transformers by natural convection of subcooled liquid nitrogen , 2003 .

[9]  G. Swift,et al.  A fundamental approach to transformer thermal modeling. I. Theory and equivalent circuit , 2001 .

[10]  Eric Van den Bulck,et al.  Modelling of the mass flow distribution around an array of rectangular blocks in-line arranged and simulating the cross-section of a winding disc-type transformer , 2001 .

[11]  G. Olivier,et al.  3-D computation of transformers overheating under nonlinear loads , 2005, IEEE Transactions on Magnetics.

[12]  N. Narayana Rao,et al.  Elements of engineering electromagnetics , 1977 .

[13]  R. D. De Doncker,et al.  Calculation of losses in ferro- and ferrimagnetic materials based on the modified Steinmetz equation , 1999, Conference Record of the 1999 IEEE Industry Applications Conference. Thirty-Forth IAS Annual Meeting (Cat. No.99CH36370).

[14]  Andrei G. Fedorov,et al.  Turbulent natural convection heat transfer in an asymmetrically heated, vertical parallel-plate channel , 1997 .

[15]  Mathew Kinyanjui,et al.  Numerical study of free convection turbulent heat transfer in an enclosure , 2004 .

[16]  Jacek Smolka,et al.  Numerical modelling of thermal processes in an electrical transformer dipped into polymerised resin by using commercial CFD package fluent , 2004 .

[17]  Risto Mikkonen,et al.  Effective thermal conductivity in HTS coils , 2000 .

[18]  S. Maksimovic,et al.  Non-stationary thermal model of indoor transformer stations , 2002 .

[19]  K. Preis,et al.  Thermal-electromagnetic coupling in the finite-element simulation of power transformers , 2006, IEEE Transactions on Magnetics.

[20]  K. Hanjalić,et al.  Application of infrared thermography to the evaluation of local convective heat transfer on arrays of cubical protrusions , 1997 .

[21]  Derek B. Ingham,et al.  Enhanced numerical model of performance of an encapsulated three-phase transformer in laboratory environment , 2007 .

[22]  S. Ryder,et al.  A Simple Method for Calculating Winding Temperature Gradient in Power Transformers , 2002, IEEE Power Engineering Review.

[23]  K. Preis,et al.  On the use of the magnetic vector potential in the finite-element analysis of three-dimensional eddy currents , 1989 .

[24]  Saffa Riffat,et al.  Accuracy of CFD for predicting pressure losses in HVAC duct fittings , 1995 .

[25]  Jiri Blazek,et al.  Computational Fluid Dynamics: Principles and Applications , 2001 .

[26]  Eric Van den Bulck,et al.  Modelling of the mixed convection in the windings of a disc-type power transformer , 2000 .

[27]  S. R. Mathur,et al.  Finite Volume Method for Radiative Heat Transfer Using Unstructured Meshes , 1998 .

[28]  B. Launder,et al.  Application of the energy-dissipation model of turbulence to the calculation of flow near a spinning disc , 1974 .

[29]  G. Raithby,et al.  COMPUTATION OF RADIANT HEAT TRANSFER ON A NONORTHOGONAL MESH USING THE FINITE-VOLUME METHOD , 1993 .