Imporvement of New Synthetic Power Quality Indexes: an Original Approach to Their Validation

In the paper the authors propose the improvement of three new power quality indexes presented in a previous work (De Capua, 2004) for exhaustively detecting voltage sags. In fact, during the indices´ experimental assessment, some weak points of the previous presented indices have arisen. After indices´ correction, ANOVA analysis have been performed, in order to investigate indices´ sensibility with regards to sag depth and duration. At this aim a full experimental analysis has been conducted by applying a multilevel multivariable experiment. Through ANOVA analysis, moreover, a cost function has been realized to correlate the indexes values to the effective cost of lost quality for users who need the absolute absence of sag occurrence. Subsequently the indices´ uncertainty has been estimated; a random-fuzzy technique has been preferred, since the ISO guide shows its limits in presence of DSP-based algorithms