Impactos do dimensionamento da corrente de magnetização de transformadores na coordenação de funções de proteção de sistemas elétricos

Abstract

The impact of transformers’ inrush currents on overcurrent protection functions is evaluated in this work. To do so, simulation tests are carried out in power systems reported in the literature as well as in real distribution networks located in the region of Petrolina– PE. Basically, the power grids are simulated in the ANAFAS software, in which the three-phase and single line to ground fault currents are computed. These short circuit current values are used as input data in the OCTAVE software to set the instantaneous- and the time-overcurrent protection functions, as well as the transformer’s inrush cur- rent. The overcurrent functions outputs are provided to the user as the utility and consumer time-characteristic curves, indicating also the respective inrush current point in the same plot. From the obtained results, the transformer’ inrush current can directly impact on the overcurrent protection coordination, affecting the protection studies of companies fed by transformer units. In these cases, the incorrect set of such magne- tizing current influence on the protection system reliability, and it may also lead to the protection study disapproval by the utility.