Indices for Harmonic Distortion Monitoring of Power Distribution Systems

Among different power quality parameters, the voltage total harmonic distortion is important and often-analyzed category. Different indices have already been suggested to measure and to monitor both the current and the voltage distortion in power systems, but harmonic site characterization still cannot be performed in satisfactory way. The state of the harmonic distortion is difficult to predict due to variability and a large number of unknown, such as detailed consumer and system characteristics. In this paper a new index describing the total harmonic distortion in current measurements, total rated distortion (TRD), is suggested in order to simplify and standardize harmonic current measurements. Another index representing the increase of harmonic voltage distortion with TRD, equivalent harmonic impedance z_eq, is proposed as an efficient way of characterizing a particular site. Finally, extensive harmonic measurements of a real distribution system were performed to prove the usefulness of the proposed indices.