Electric Field Strength and Spray Thickness Effect on Frequency Domain Dielectric Properties of Epoxyimpregnated Paper

This study systematically investigates the frequency domain spectroscopy properties variation patterns of epoxyimpregnated paper coated with epoxy varnish under different temperatures, AC voltage, and spray painting thickness conditions. The experimental results indicate that under high electric field strength, partial discharge and charge migration phenomena are significantly enhanced, leading to a nonlinear increase in dielectric constant and dielectric loss--tan <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\delta$</tex>, which suggests a potential threat to the material's insulation performance under high electric field conditions. Additionally, an increase in spray painting thickness improves the surface insulation performance of the material, reducing surface charge accumulation and local electric field concentration, thereby significantly decreasing dielectric loss. Furthermore, as the temperature rises, the imaginary part and tan <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\delta$</tex> of the epoxy-impregnated paper increase notably, primarily due to intensified molecular thermal motion and enhanced polarization capability within the material at elevated temperatures. High temperatures may also induce material aging, further exacerbating energy loss. Through comprehensive experimental analysis, this study reveals the synergistic mechanism of temperature, electric field strength, and spray painting thickness on the frequency domain spectroscopy properties and dielectric loss of epoxy-impregnated paper, providing crucial experimental evidence for optimizing material design and practical applications. These results not only contribute to a deeper understanding of the variation patterns of the insulation performance of epoxy-impregnated paper but also offer scientific guidance for the selection and maintenance of insulation materials in electrical equipment.