5. Forming and Filtration of Measurement Waveforms

This chapter, the processes of forming and filtration of measurement waveforms are described. The measurement waveform processing was performed in the following stages: determination of generator power angle, calculation of axial components of generator stator currents and voltages, determination of base quantities and quantities in relative units (including field voltage and current), waveform filtration, change in sampling frequency, calculation of mean values of waveforms in steady state for the synchronous generator XT model, scaling of the field current and voltage waveforms so that their relative values are equal to each other in steady state. Due to the non-periodic nature of measurement dynamic waveforms, their analysis in terms of determining a useful signal band and selecting filter parameters was carried out using a short-time (windowing) Fourier transform. Finally, linear-phase digital low-pass FIR filters available in the Matlab Filter Design Toolbox package were used for zero phase filtration of the measured and recorded dynamic waveforms. The parameters of the designed filters were each time individually selected for the recorded measurement waveforms.