Voltage unbalance monitoring in CEB systems

Although the subject power quality has been treated by specialists of the area, it´s incipient the number of investigation works referring to voltage unbalance. In this interim, the purpose of this work is to analyze, quantify and qualify the voltage unbalance, so that the results obtained here should be useful not only minimize harmful effects on the power system, as well as making a database containing valuable information about amplitudes and the behavior of the voltage unbalance. Initially, the 4 existing methods are described for the calculation of the voltage imbalance (K factor). From numeric results and from the profile of the K factor, a comparison of the methods is made. The behavior of K is analyzed when the modules and angles of the voltage phasors are variated. After that, the quantification and qualification of the K factor are made, according to the main norms (standards) word wise known for several measured places. Of the foregoing analyses, it can be concluded that the period of measurement of 1-week day is enough for the study of the K factor. Additionally, the method of CIGRE is recommended when voltage angles can´t be measured.