Frequency-Domain Analysis of Contaminant Effects on Leakage Current and Harmonic Distortion for Transmission Line Diagnostics

Environmental contaminants such as dust, moss, and flashover residue significantly impact the performance of highvoltage ceramic insulators by altering dielectric properties and increasing leakage current (LC). This study investigates the effect of natural contamination using Fast Fourier Transform (FFT) and harmonic analysis on insulators exposed to realworld conditions in Payakumbuh Koto Panjang. The results indicate that dominant frequencies remain near 50 Hz, with minor shifts (49.95 Hz for moss, 50.06 Hz for dust), highlighting their sensitivity to environmental variations. Magnitude analysis reveals that dust contamination exhibits the highest dominant magnitude (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.54 \times 10^{-4}$</tex>), indicating stronger energy retention, while harmonic analysis up to the fifth order shows that dust contamination induces the most significant distortions. Flashover residue exhibits a unique harmonic decay pattern due to carbonization effects. Total Harmonic Distortion (THD) analysis confirms that contamination leads to increased harmonic interference, suggesting its potential as an early indicator of insulation degradation. These findings contribute to the development of predictive maintenance strategies for highvoltage transmission systems, enhancing insulation reliability in extreme environmental conditions.