Power quality evaluation indices in three-phase networks

The large use of nonlinear and time-varying single- phase and three-phase loads produces current waveform distortion. Their interactions with the power supply system has made that the industrial electrical consumer systematically need measure equipment to evaluate the electric power quality. The measurements show that the harmonics of the waveforms and the unbalance are variable along with the time due to the changes in the load conditions and in the system configuration. Thus, due to the use of commercial analysers, the electrical users dispose of a great quantity of data from such of the three phases of the supply. Therefore, it is necessary to find a way to characterize this great group of registered data. In this work two indices are proposed: a three-phase total demand distortion index and a total unbalance index. Besides, this paper proposes an easy way to characterize, statistically, the groups of data to simplify their representation. The study carried out is applied to the data registered in an electrical power system.