Uma proposição de novos protocolos de medição sob a ótica da qualidade da energia elétrica

Abstract

Nowadays most of the problems in electrical engineering are related to Power Quality concerning subjects. Usually, several measures are adopted in power devices to produce and maintain alternating voltages and currents as close as possible to sinusoidal waveforms. However, a number of causes tend to distort these signals. Rectification of alternating current and other kind of non-linear load produces a non-sinusoidal current. The presence of non-linear loads in the networks also distorts voltages across the terminals of linear elements, producing non-linear voltage drops in the power distribution systems. Further, despite the usual employed efforts, the utilities are not able to keep the voltages balanced. The load unbalance usually deteriorates the performance of the electrical systems. In the circumstances in which these two undesirable power phenomena happen, this doctorate thesis deals with the definition of apparent power in three phase systems and its active and non-active power components. It is shown a no conventional solution to take in account how the power factor is affected by no linearity and unbalance; in the presence of non-sinusoidal waveforms and unbalanced signals, the global power factor can be defined as a product of three terms: displacement power factor, the distortion power factor and the unbalance power factor. In order to evaluate the technical feasibility of the proposed measurement method and to verify the validity of the theoretical considerations, a prototype has been assembled. The behavior of the prototype was the expected and results of the measurements were in agreement with the results of the simulation by means of the MatLab program.