Epoxy/impregnated-paper multilayer composites serve as the primary insulation in UHV/EHV resin-impregnated- paper (RIP) bushings

yet the dielectric properties of the impregnated-paper layer cannot be measured directly and accurately

severely constraining frequency-domain dielectric analyses under temperature-gradient conditions. From the perspective of the complex electric modulus

this paper identifies a dual-relaxation process in the epoxy/impregnated- paper composite at temperatures above 60 °C. Using a dual Havriliak-Negami (HN) model that incorporates DC conduction

this paper fits the dielectric data and clarify that the dielectric relaxation comprises σ-polarization associated with the crepe paper and interfacial polarization. By constructing a parallel RC equivalent-circuit model for the multilayer composite and combining it with image-based volume-fraction recognition

this paper accurately determines the frequency-domain dielectric parameters of the impregnated- paper layer. On this basis

a temperature-frequency decoupling modeling method for the dielectric-parameter dependence in epoxy/impregnated- paper is proposed

and the internal electric-field distribution and frequency-domain dielectric response of a multilayer composite model across different temperature-gradient ranges are simulated. The results indicate that the electric-field jump across the epoxy/impregnated-paper interface on the high-temperature side is the largest

and that this discontinuity becomes increasingly pronounced as the frequency decreases. This work overcomes the limitations of traditional measurement methods and enables precise analysis of dielectric properties and electric-field distributions in multilayer composite insulation under temperature-gradient conditions.