The paper presents the questions of the accuracy of electric waveforms (current and voltage) by their spectrum, determined in accordance with the standards dedicated to the analysis of current quality. There has been also presented the voltage waveform, recreated from the spectrum that was obtained in accordance with the norm. It has been shown that for 3 different system frequencies, determined by the norm spectrum cutoff of up to 50 components may lead to the elimination of harmonics of significant values. Moreover, the volume of inter-harmonics and their impact on the voltage waveform has been analyzed. Exemplary results of measurements done with power quality analyzer in the laboratory have been presented.

Keywords: Harmonics, Inter-harmonics, Power quality analyzer, Measurements, Standards, Fourier transform