Semi-conductive buffer layer for the conductor-insulator interface of HVDC GIS/GIL

In high voltage direct current (HVDC) gas-insulated switchgear (GIS) and gas-insulated transmission lines (GIL), epoxy resin and its composites serve as the primary insulating components. However, the inherent mismatch in mechanical properties at the interface between the metal conductor and epoxy-based insulator gives rise to weak points during production and operation, leading to potential issues like physical cracking or electric field distortion. In this work, these challenges are addressed by introducing a semi-conductive buffer layer with rationally modulated electrical and mechanical properties at the conductor/insulator interface. Carbon black nanofillers are incorporated into a polyether-amine cured epoxy matrix for optimal performance. The application of such a buffer layer significantly improves the bonding strength between the epoxy-based insulator and the aluminum conductor, which also effectively inhibits charge injection from metal conductors to GIS/GIL insulators. To ensure industrial applicability, storage modulus, glass transition temperature and coefficient of thermal expansion of the semi-conductive materials are systematically investigated. The design of semi-conductive buffer layer provides a feasible approach to enhancing the mechanical and electrical performance of HVDC GIS/GIL systems.