Evaluation of Moisture Content in Insulating Oil of Cable Terminals Utilizing Terahertz Technology

The insulating oil in oil-filled high-voltage cable terminals is critical for operational safety, yet moisture ingress over time can degrade its insulation properties. This study explores terahertz time-domain spectroscopy (THz-TDS) as a non-destructive method for detecting moisture in insulating oil. Five silicone oil samples with varying moisture levels were prepared through natural absorption. THz-TDS was employed to analyze their time-domain and frequency-domain spectra, and key parameters, including extinction coefficient, absorption coefficient, and dielectric constant, were derived using the Fresnel formula. Traditional methods were used to validate the THz-TDS results, ensuring accuracy. The findings demonstrate that THz-TDS effectively detects moisture content changes in insulating oil, offering a potential solution for real-time, online monitoring in high-voltage cable systems. This approach provides a rapid, reliable, and non-invasive diagnostic tool for maintaining cable integrity and preventing insulation failures.