Spectral Analysis of Electrical Discharge in Mineral Oil—Comparison With Air Discharge

This study aims to compare the spectral characteristics of electrical discharges in mineral oil (MO) with those in air. The results demonstrate that electrical discharge channels in MO exhibit a resistive nature, as evidenced by the phase difference, and that discharges in this medium are associated with higher energy levels due to their superior dielectric strength. This necessitates higher voltages for discharge initiation compared to electrical discharges in air, which involve lower energy levels due to air’s lower dielectric properties. Temporal domain analysis shows that electrical discharges in air propagate faster than those in MO. In addition, fast Fourier transform (FFT) analysis reveals that air discharges exhibit a broader spectrum with more high-frequency components, indicating faster propagation than MO discharges. The differences in dielectric properties—such as dielectric strength, breakdown voltage, density, and viscosity—are lower in the air than in MO, significantly influencing discharge characteristics, including current, voltage, power, and energy. These findings offer crucial insights into the nature of discharge channels, energy levels, propagation speeds, and discharge dynamics in air and MO. This contributes to developing more effective insulation monitoring and predictive maintenance strategies in electrical power systems.