A Method to Separate Harmonic Current Flows According to the Directions of their Sources in a Distribution Substation

Abstract

It is necessary to detect sources of harmonic currents in order to reduce harmonic voltage distortion in an electric power distribution system. For this purpose, it is very important to judge the direction of a harmonic current flow, so far, there is no method to judge the direction of flows precisely, This report presents a method to separate transformer currents at a distribution substation into two elements quantitatively; one that flows into a distribution system due to harmonic voltages in a higher voltage system, and the other that flows to a higher voltage system due to sources of harmonic currents in a distribution system. The conventional method to judge the direction of flows using phase angles between harmonic voltages and harmonic currents may not be accurate. By using the newly developed method, the direction of harmonic current flows can be analyzed quantitatively and more accurately than the results by the conventional method. Measured values in both a business area and a residential area are analyzed to verify the new method and the results clearly show the difference of the characteristics of the two areas.