A Novel Software Tool For Power Quality Diagnosis

This paper focuses on a novel automatic software tool to locate three major power quality disturbances, i.e. voltage sag, transient and harmonic. The software tool developed is to locate the source of these disturbances relative to a monitoring point. The methods employed in the software only require the current and voltage data. For locating the source of voltage sag, the product of the RMS current and the power factor angle at the monitoring point is employed and the complex wavelet-based energy is employed for locating the source of transients. A new method to determine the source of harmonic at the point of common coupling as to whether it is from the upstream or downstream is based on the harmonic Thevenin circuit. The proposed methods are written in MATLAB V. 7 and graphic user interface software is developed to automate the new methods. This new software has been tested using both real and simulation data and it is very fast, simple and accurate to locate the power quality disturbances.