New power-quality assessment criteria for supply systems under unbalanced and nonsinusoidal conditions

Power-quality monitoring is a very complex task and recently it is assuming a growing importance because of the large diffusion of nonlinear and time-varying single-phase and three-phase loads and their interactions with the power supply system. A set of two indexes capable of evaluating the power quality at the point of common coupling (PCC) in terms of harmonic distortion and unbalance is proposed in this paper. By means of these new performance parameters, which are based on voltage and current waveform measurements at the PCC, it is possible not only to evaluate separately unbalance and distortion, but also to localize polluting loads and separate the responsibilities of distributors and customers. Numerical simulations and experimental tests prove the effectiveness of the presented indexes and their low sensitivity to the network voltage conditions compared with the traditional ones.