3D modeling of winding hot spot temperature in oil-immersed transformers

The temperature of windings hot spot is a factor affecting the load capacity and useful life of power and distribution transformers. It is the hottest point of transformer in terms of design and measurement in all components of the transformer. The temperature of oil and windings of transformers, especially windings hot spots, can accelerate destruction of cellulose paper such that the most common cause of transformer failure is collapse of insulation. In this study, we performed the temperature rise test on a copper distribution transformer with a power of 200 kVA in accordance with the IEC standard in several steps. The accurate sensors recorded the top, bottom oil and ambient temperature. In addition, the ohmic resistance of the windings was measured in the first stage and at the end of the test to calculate the hot spot temperature of windings. Finally, the results were compared according to the Computational fluid dynamics (CFD) method via the three-dimensional drawing of the same transformer by ANSYS Design modeler and its thermal modeling including windings, core, and active part display using ANSYS fluent software. Evaluation of the two analyses revealed that the percentage of relative errors of results was negligible; thus, transformer designers can use the CFD method in their research.