Enhancing electrical insulation of epoxy composites by suppressing charge injection and subsequently electric field distortion

Epoxy composites with flame-retardant fillers are key electrical insulation materials for dry-type high-voltage (HV) transformers, but the ionic structure nature of the flame-retardant fillers can lead to the deterioration of the insulation performance, limiting the reliability of HV power systems. This study systematically examines how flame-retardant filler introduction and interface structure evolution impact charge transport within composites, aiming to refine the design principles of flame-retardant electrical insulation materials. Composites with uniformly dispersed fillers and ideal interfacial bonding with the matrix exhibit improved resistivity (1.41 × 10 16  Ω cm), attributed to the dense cross-linked network that limits impurity ion movement. More importantly, the behavior of space charge accumulation and dissipation within the composites indicates that the interfacial structure affects the internal energy level distribution, thereby influencing charge carrier transport characteristics. By optimizing the interfacial structure, the suppression of electrode charge injection and reduction of electric field distortion (from 15.1 % to 8.5 %) enhance the electrical insulation reliability of epoxy composites. These findings deepen the understanding of structure-property relationships in epoxy composites, offering critical insights for designing advanced flame-retardant HV electrical insulation materials.