Purpose ‐ The purpose of this paper is to compare the accuracy of tracking the amplitude and frequency changes of non-stationary electric signals. Design/methodology/approach ‐ Short-time fourier transform (STFT) and S-transform algorithms were applied to analyze non-stationary signals originating from switching of capacitor banks in a power system. Findings ‐ The S-transform showed possibilities of sharp localization of the basic component, and allowed improvement of tracking dynamism the transient components in comparison to STFT. Practical implications ‐ S-transform is a better tool for the analysis of non-stationary waveforms in power systems and its properties can be used for diagnostic and power quality applications. Originality/value ‐ The dynamic tracking of the changes in time and frequency of real-like signals originating from a power system are investigated in this paper.