High-Stability graphene/copper conductors with enhanced electrical and mechanical performance for transformer windings

Graphene/copper (Gr/Cu) composite conductors are promising alternatives to conventional copper in transformer windings, yet their long-term reliability in insulating oils remains insufficiently explored. In this work, Gr/Cu conductors fabricated by chemical vapor deposition were subjected to accelerated thermal aging at 130[Formula: see text]C for 800 h in mineral oil, with complementary tests in natural ester oil and air. Key performance indicators, including electrical conductivity, tensile strength, and elongation, were systematically evaluated using Cu conductors as a reference. The Gr/Cu conductors maintained high conductivity (104.79–119.41% IACS, average 109.87%), stable tensile strength (230.26–236.71 MPa), and elongation up to 39.10%, significantly outperforming Cu counterparts. Microstructural analyses showed that the dislocation density of Gr/Cu after aging (1.51 × 10[Formula: see text]m[Formula: see text]) remained lower than Cu (2.09 × 10[Formula: see text]m[Formula: see text]), and the reduction in the full width at half maximum of the Cu (200) crystallographic diffraction peak was smaller (0.020[Formula: see text] versus 0.033[Formula: see text]), confirming that graphene effectively suppressed dislocation accumulation and grain coarsening. These mechanisms collectively enhanced electrical retention, mechanical stability, and interfacial reliability under coupled thermal-oxidative stresses. The findings highlight the strong potential of Gr/Cu conductors for next-generation high-reliability transformer applications.