Characterization of unbalanced and distorted distribution systems from experimental data

The basic concepts for assessing the characteristics of unbalance and harmonic distortion in the general case of a distribution system operating in unbalanced conditions and with distorted waveforms have been introduced by the authors in a specific symmetrical component-based (SCB) framework. The adoption of the indicators defined in the SCB framework allows obtaining effective results by measuring the electrical waveforms according to the measurement criteria indicated in the standard IEC 61000-4-7. In particular, starting from the waveforms measured on a real low-voltage distribution feeder, it is shown how the total phase distortion (TPD) indicator introduced in the SCB framework provides results equivalent to the use of weighted total harmonic distortion indicators assuming the squared RMS phase currents as weights.