Electromagnetic-thermal evaluation of different non-magnetic material configurations for power transformer tank cover

This study investigates the effectiveness of non-magnetic materials used in the cover plates of power and distribution transformers. In transformers with large nominal power ratings, the current flowing through the low voltage (LV) windings can reach values in the thousands of amperes. This substantial current generates a strong magnetic field within the transformer tank and cover plate. A common method to mitigate the associated ohmic losses, known as stray losses, is the application of magnetic shunts. However, due to the geometric complexity of the cover plate, the use of magnetic shunts is not feasible for this component. Alternatively, a practical approach to reduce stray losses and prevent overheating of the cover plate is the incorporation of non-magnetic materials between the LV bushings on the cover plate. It is important to note that the stray losses discussed here primarily arise from eddy currents induced in nearby metallic structures, not from ohmic losses within the LV windings themselves. This research proposes five different design scenarios involving non-magnetic segments, commonly used in transformer manufacturing, to be integrated into the cover plate. These scenarios are simulated and analyzed using the Finite Element Method (FEM). Both the ohmic losses induced by magnetic flux penetration in the cover plate and the resulting temperature distributions are thoroughly examined and compared across all cases. The findings demonstrate that the use of non-magnetic material segments significantly reduces stray losses and lowers the temperature of the cover plate. Among the proposed designs, the rectangular-shaped non-magnetic segment, positioned over the high-current region of the cover plate, exhibited the most favorable performance compared to the other configurations. • Power Transformer. • Energy Efficiency. • Transformer Stray Losses. • Transformer Cover Plate.