Surface Hardness Analysis of Aged Composite Insulators via Laser-Induced Plasma Spectra Characterization

Silicone rubber composite materials, especially high-temperature vulcanized (HTV) insulators, are widely used in high-voltage transmission lines. Previous studies have shown that the degree of aging of an HTV material is approximately linear with its hardness. The hardness measurement relies on laboratory analysis after sampling, and there is no alternative hardness test available for on-site application. In this paper, the ablation characteristics of HTV materials and the spectral and temperature characteristics of the corresponding plasmas were investigated via laser-induced breakdown spectroscopy (LIBS), thereby laying the foundation for the subsequent use of LIBS technology for on-site hardness characterization. A linear relationship was found between the hardness (either macroscopic or microscopic) of an HTV material and the intensity ratio of the ion line to the atomic line in the spectral data as well as a linear relationship between the hardness and the average plasma temperature corresponding to the aging layer. The results show that LIBS can serve as an effective source of hardness information for an HTV material and is therefore helpful for maintaining the safety of transmission lines.