Rapid Detection Method for Moisture Mass Fraction in XLPE Main Insulation Layer of Cable Joints

A near-infrared spectroscopy method was proposed to detect moisture mass fraction in cross-linked polyethylene (XLPE) cable joints, addressing the long-standing lack of an on-site detection method in cable operation and maintenance. Experiments were conducted using 10 kV XLPE three-core cable samples with service life ranging from 5 to 20 years. Moisture mass fraction was determined using evaporation weighing method, providing reference values for establishing the standard curve. Near-infrared spectra were collected using a Fourier-transform near-infrared spectrometer and a dedicated spectral sampling accessory. Based on an in-depth spectral analysis, a standard curve was established using the first-order differential value of hydroxyl group at 1450 nm and the moisture mass fraction. Results showed that coefficient of determination for the standard equation was 0.90958, and relative deviation of predicted values from the new method was less than 4% compared with evaporation weighing method. The new method is simple to operate, requires a short testing time, and is suitable for on-site detection. It has significant practical value in improving the efficiency of cable joint replacement and reducing cable operation costs.