The thermal dynamics of windings in oil-immersed transformers are crucial for ensuring operational safety and extending service life. Excessive winding temperatures accelerate insulation degradation, amplify energy dissipation, and may precipitate critical failures. Therefore, a comprehensive examination of winding temperature dynamics under diverse operating conditions is imperative for optimizing transformer thermal management and enhancing reliability. This study formulates a magneto-thermal-fluid coupling model, merging the finite volume method (FVM) with computational fluid dynamics (CFD) to systematically investigate the thermal characteristics of windings under three representative conditions: normal operation, overload, and oil circuit blockage. Under normal conditions, the principal attributes of winding temperature distribution are delineated, with particularly focusing on the interaction between oil flow dynamics and thermal gradients. Under overloaded states, the thermal response of windings at varying overload levels is simulated, elucidating the evolution of hot-spot temperatures and the variability in temperature gradients. In the event of oil circuit blockage, the study rigorously assesses the repercussions of restricted oil flow on heat dissipation, focusing on the mechanisms that lead to localized overheating. The research findings provide theoretical guidance for refining thermal management strategies for oil-immersed transformers, and lay the groundwork for evaluating overload tolerance and for the advancement of early fault detection and diagnostic techniques.
 

Oil-immersed power transformer, Local overheating, Winding inter-turn fault.