Numerical and experimental validation of variation of power transformers’ thermal time constants with load factor

Thermal time constants (TTC) of a thermal dynamic model reflect the change rate of temperature, which are affected by many factors such as load current, oil temperature, etc. In this study, relative thermal time constants (RTTC) are introduced and formulated to describe the variation of thermal time constants with load current. It is verified through extensive case studies based on computational fluid dynamic (CFD) simulation and field measurements. Specific for CFD simulation, the polyhedral meshing was applied to mesh division of 3D model due to narrow part such as discs in transformer. The proposed relative thermal time constants can be integrated with dynamic thermal model to estimate the hot-spot temperature of transformers, especially in overload situations. Accuracy and adequacy metrics are used to quantify the accuracy of presented thermal model with proven thermal model.

[1]  M. Lehtonen,et al.  Dynamic thermal modelling of power transformers , 2004, IEEE Transactions on Power Delivery.

[2]  Jacek Smolka,et al.  Experimental validation of the coupled fluid flow, heat transfer and electromagnetic numerical model of the medium-power dry-type electrical transformer , 2008 .

[3]  D. J. Tylavsky,et al.  Acceptability of Three Transformer Hottest-Spot Temperature Models , 2012, IEEE Transactions on Power Delivery.

[4]  Vitaly A. Yatsevsky.  Hydrodynamics and heat transfer in cooling channels of oil-filled power transformers with multicoil windings , 2014 .

[5]  James L. Kirtley,et al.  An improved transformer top oil temperature model for use in an on-line monitoring and diagnostic system , 1997 .

[6]  Mario Alberto Storti,et al.  Numerical and experimental thermo-fluid dynamic analysis of a power transformer working in ONAN mode , 2017 .

[7]  Alistair Revell,et al.  Numerical prediction of local hot-spot phenomena in transformer windings , 2012 .

[8]  F. Torriano,et al.  Numerical study of parameters affecting the temperature distribution in a disc-type transformer winding , 2010 .

[9]  L. W. Pierce.  Predicting liquid filled transformer loading capability , 1992, [1992] Record of Conference Papers Industry Applications Society 39th Annual Petroleum and Chemical Industry Conference.

[10]  Jacek Smolka,et al.  CFD-based 3-D optimization of the mutual coil configuration for the effective cooling of an electrical transformer , 2013 .

[11]  Erik Etien,et al.  Improving thermal model for oil temperature estimation in power distribution transformers , 2017 .

[12]  Thomas Redel,et al.  Tetrahedral vs. polyhedral mesh size evaluation on flow velocity and wall shear stress for cerebral hemodynamic simulation , 2011, Computer methods in biomechanics and biomedical engineering.

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

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

[15]  S. Ho,et al.  A Novel Approach to Investigate the Hot-Spot Temperature Rise in Power Transformers , 2015, IEEE Transactions on Magnetics.

[16]  L. F. Blume,et al.  Transformer Engineering : A Treatise on the Theory, Operation, and Application of Transformers , 1938 .

[17]  Hui Ma,et al.  Moisture-Dependent Thermal Modelling of Power Transformer , 2016, IEEE Transactions on Power Delivery.

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

[20]  W.H. Tang,et al.  A simplified transformer thermal model based on thermal-electric analogy , 2004, IEEE Transactions on Power Delivery.

[21]  H. Nordman,et al.  Temperature Responses to Step Changes in the Load Current of Power Transformers , 2002, IEEE Power Engineering Review.

[22]  Ires Iskender,et al.  An improved thermal model for distribution transformer under unbalanced voltage conditions , 2016 .

[23]  G.N. Wu,et al.  Thermal Overshoot Analysis for Hot-spot Temperature Rise of Transformer , 2007, IEEE Transactions on Dielectrics and Electrical Insulation.

[24]  F. Torriano,et al.  Numerical investigation of 3D flow and thermal effects in a disc-type transformer winding , 2012 .