CALHEIROS JUNIOR, Eduardo Jorge.
Résumé:
Analysis of suitability of equipment are indispensable for the electric sector companies
meet the conditions in which they operate, thus ensuring the performance of the
company's assets and its availability in the National Interconnected System (Sistema
Interligado Nacional). The power transformers are included among the analyzed
equipment due to its high cost and importance for the electrical system. Most faults in
power transformers is of dielectric origin, related to insulation damage due to
mechanical deformations, caused by the high short-circuit currents in the windings,
reducing the life of the equipment. Then, it was proposed to evaluate the internal
electromechanical efforts to some power transformers present in the CHESF system,
through computer simulations, in the event of a three-phase short circuit. The
methodology for the simulations consisted to select the transformers to parse and collect
the necessary technical information provided by the manufacturers. Later, certain
systemic conditions in which the transformers would be subjected were defined, it was
obtained the resulting short circuit levels and then was performed the simulations
themselves. The results of the computer simulations showed the electromechanical
efforts estimated at four power transformers in operation in the CHESF electrical
system, resulting from the dynamic effect of three-phase short-circuit current that run
through the windings of the transformer, considering different systemic configurations.
The conclusions of the analysis results indicated possible cases of overruns of
permissible limits and reveal the importance of the transformers constructive aspects in
their ability to withstand the mechanical stress caused by short circuits.
