Uma contribuição ao estudo de sobretensões em sistemas elétricos de pequeno porte contendo cargas não - lineares

Abstract

Outsourcing of Brazilian industrial park has resulted in the proliferation of small size companies fed in medium voltage levels. These companies have generally nonlinear loads, especially alternate current to direct current converters. Low power factor resulting of this leads to the need of installing capacitors which could inversely produce over-voltages in the electric network. This work analyzes a case taken at an industry, in which was found through several measuring the low power factor as well as the current harmonics. It is shown the calculation of the capacitors rating for improvement of the power factor and the analysis of overvoltages resulting from capacitor location. For the calculation of overvoltages a method has been developed, in which the system is represented by its equivalent circuit. Using this circuit, differential equations has been established and is represented its behavior in time domain. The particular solution for this equation system yields the value of voltage for every system busbar at steady state.