Resumo

ESPINOSA DOMINGUEZ, Julio et al. Zero sequence impedance behavior inpower transformers. Analysis of special cases. Energética [online]. 2024, vol.45, n.1, pp. 64-74.  Epub 30-Mar-2024. ISSN 1815-5901.

Sequence networks make it possible to represent the elements of an electrical network during unbalanced faults, according to Fortescue's theorem presented in 1918. In the case of three-phase transformers, the equivalent sequence networks depend on the connection group of the windings and the connection of the neutral tothe ground. This paper carry out a detailed study of zero-sequence networks in power transformers, using mathematical simulation to analyze two special cases, unknown to some electrical protection specialists, in which the zero-sequence impedance can cause significant changes in short-circuit currents. The results have been obtained using theoretical and empirical methods, which have made it possible to demonstrate that transformers can behave as sources of short-circuit contribution in the presence of shunt lines. At the same time, the zero-sequence impedance is different depending on the design of the ferromagnetic core for the same connection group.

Palavras-chave : connection groups; single-phase short-circuit; transformer; zero-sequence impedance;zero-sequence network.

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