Fourier Series Analysis of Periodic Electrical Signals in Power Systems in Imo State

This study applies Fourier series analysis to characterise periodic electrical signals in distribution-level power systems serving communities in Imo State, South East Nigeria, with the objective of identifying harmonic distortion components that degrade power quality and damage electrical equipment. Power quality deterioration is a serious concern in Nigerian electricity distribution networks, where harmonic distortions introduced by nonlinear loads such as variable speed drives, fluorescent lighting ballasts, and electronic switching equipment are insufficiently monitored and regulated. Voltage and current waveforms are sampled at three distribution transformer substations in the Owerri metropolitan area using a calibrated power quality analyser operating at a sampling rate of 10 kilohertz over a 72-hour monitoring window. Fourier series decomposition is performed on the recorded waveforms to extract harmonic components from the third to the twenty-fifth order, and total harmonic distortion indices are computed for each measurement point. Results are evaluated against the IEEE Standard 519-2022 harmonic distortion limits and the standards promulgated by the Nigerian Electricity Regulatory Commission. Findings indicate that total harmonic distortion in voltage waveforms at two of the three substations exceeds regulatory thresholds during periods of peak commercial activity, primarily attributable to concentrations of single-phase nonlinear loads in adjacent market areas. The study recommends the installation of passive harmonic filters and the implementation of a systematic power quality monitoring programme by the Imo State distribution company. Keywords: Fourier series, harmonic distortion, power quality, electrical signals, Imo State