Exact Voltage Unbalance Assessment Without Phase Measurements

Abstract

In this letter, it is shown that the positive- and negative-sequence components of a three-phase, sinusoidal and unbalanced voltage system can be calculated exactly without the application of the Fortescue transformations in the complex plane, while only the root mean square (RMS) line-to-line voltages are required, and without having to measure the phase relationships between these voltages. This results in a convenient procedure to assess voltage unbalance in the field. The phase relationships between the sequence and line components can also be calculated. Moreover, if the RMS values of the line-to-neutral voltages are known, the zero-sequence component can be calculated exactly as well, again, without the application of complex mathematics.