Estimação computacional dos esforços eletromecânicos em transformadores de potência no sistema CHESF.

Abstract

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.