Research on the principle of measuring the relative permittivity of glass insulators based on laser-induced breakdown spectroscopy

In response to the demand for online detection of insulator insulation strength in power systems, we investigates the principle of relative permittivity <i>ε_r</i> detection for SiO₂-based glass insulators using laser-induced breakdown spectroscopy (LIBS). The influence of relative permittivity on ablation and radiation spectra is explored by a nanosecond pulsed laser ablation radiation model for the SiO₂ material. With the relative permittivity varying from 1.49 to 2.25, the reflection of SiO₂ to the incident laser is enhanced. The laser energy deposited on the surface of the target decreases, resulting in a linear decrease in ablation depth and surface temperature. During the expansion and ionization of the plasma plume, the peak temperature of the plume decreases by approximately 3000 K, and the peak electron density decreases by 6×10²³ m^-3 at t=150 ns. The simulation of LIBS emission spectra at the edge of the plume reveals that both line peak intensity and Stark broadening decrease with the relative permittivity <i>ε_r</i>. We found that the net peak intensity of characteristic spectral lines O I 615.818 nm, O I 645.598 nm, Si I 672.185 nm, and Si 697.652 nm decreased monotonically with the increase of relative permittivity ε_r. The research findings presented in this paper provide theoretical support for utilizing LIBS technology to achieve detection of insulation strength in SiO₂-based glass insulators.