A Power-Quality Measure

A power-quality (PQ) measure is introduced in this paper. The proposed measure, based on the Shannon's entropy, expresses the deviation of the examined voltage cycle from the ideal one. Two entropy concepts are introduced—the spectral and the probabilistic entropy. The two entropies, calculated for every voltage cycle, are properly combined to provide the PQ measure. The PQ measure is represented graphically on a 2-D Cartesian coordinate system. The PQ measure is calculated for the most common PQ disturbances. The graphical representation of the calculated PQ measurements leads to the definition of an area of acceptable PQ on the PQ measure 2-D diagram. The PQ of a power system may be evaluated by the proposed measure, by implementing voltage measurements during predetermined time periods in selected network nodes. The produced electricity price may be configured in terms of the measured PQ.