Influence of Different Turret-Tank Connection Types on Transformer Turret Eddy Currents

摘要

All metal parts of the transformer tank are usually electrically connected and grounded in order to prevent the possibly hazardous floating potential from emerging. The magnetic field of transformer leads and bushings' conductors induces eddy currents on nearby metal parts such as tank top and bushing turrets. Since the above-mentioned electrical connections can form the unwanted conducting path loops, the type of these connections can help in restricting the eddy currents and consequently the losses in metal parts and the heat generated in them. This is especially true for high-current power transformers such as generator step-up units. This research presents calculated and measured results of the influence of different bushing turret-tank connection types on the induced eddy current values. The simulation results were obtained using the finite element method based software. Comparison against the measurements shows that these eddy currents can be adequately modelled and predicted using calculations which can prove useful in the design phase of the transformer manufacturing process. By carefully choosing the connection type and the location of the shorting element, the eddy current conducting path loops can be restricted and therefore the values of these currents can be limited as well. This can, in turn, lead to lower local losses and reduced heating of the metal parts, all of which can be easily shown using Rogowski coils for current measurements and thermal imaging systems for thermography measurements, respectively.