Harmonic power flow determination using the fast Fourier transform

Multichannel data acquisition systems and commercially available digital signal processing software packages make the determination of harmonic power flow possible provided the limitations of the analysis techniques are understood. The authors describe how data from a typical acquisition system can be processed using the fast Fourier transform and discuss possible errors (e.g. those due to leakage) and how to avoid them using techniques such as skewing correction and windowing. Guidelines on the practical application of the transform in analyzing measured data are presented. The analysis method has been used successfully to analyze data obtained at a traction (railway supply) substation which had a sixth-harmonic resonance caused by the interaction of a harmonic filter and the only supply system