Research on Fluorescent Penetrant Inspection and Plasma Modification of Surface Microcracks in Silicone Rubber Composite Insulators

ABSTRACT

Surface microcracks in silicone rubber composite insulators can cause electric field distortion, which may ultimately lead to insulation failure. To address the strong subjectivity and susceptibility to environmental interference associated with traditional inspection methods such as manual patrols, ultrasonic testing, and infrared detection, this study proposes a microcrack fluorescent penetrant inspection (FPI) method combined with image recognition. A water‐based fluorescent penetrant was sprayed onto the sample surfaces to construct a self‐built dataset, which was then used to train a YOLOv5 model. After 100 training epochs, the precision for microcrack recognition reached 93%. To mitigate the adverse effects of the penetrant and microcracks on surface insulation performance, plasma jet treatment was applied to modify the microcracked regions of the samples. After 3 min of Ar/HMDSO plasma treatment, the flashover voltage increased from 7.46 to 8.89 kV, representing an improvement of 16.4 % compared with the untreated condition. Meanwhile, the water contact angle increased from 113.5° to 142.9 ± 0.2°, corresponding to an enhancement of 25.9 %. XPS and optical emission spectroscopy analyses indicate that plasma modification introduces low‐polarity silicon‐containing groups, such as Si‐O‐Si and Si‐(CH ₃ ) _x , which reduce the surface energy of the material and thereby promote improved hydrophobicity.