Evaluation of Power Transformer Thermal Performance and Optical Sensor Positioning Using CFD Simulations and Temperature Rise Test

The internal temperatures and the ability to dissipate the heat from active part influence the windings' insulation deterioration and determine how long power transformers are able to remain in operation. Due to the great importance of this equipment for the electrical system, studies to avoid failures and early aging are needed. This article presents an evaluation of thermal performance of power transformers and the optical fiber sensor positioning to temperature monitoring. For this, an experimental and numerical methodology is performed, comparing the measurements during the temperature rise test of single-phase prototype power transformer, under oil directed and air natural (ODAN) cooling system conditions equipped with 20 optical fiber sensors along its windings, to the obtained results of computational fluid dynamics (CFD) simulations performed in ANSYS Fluent software. It was verified that the punctual temperature measured by optical sensors may not accurately represent the critical temperatures along transformers' windings, and the windings' arrangements impact on oil flow and temperature distribution, as the number and positioning of block washers being necessary to be considered in previous studies for a better positioning of the sensors and temperature monitoring.