Effectiveness and Robustness Design of 500 kV HVDC Presaturated Iron-Core Fault Current Limiters

This paper presents a novel full-scale compact design of $500\ {\text{kV}}$ HVDC, with rated pre-fault steady-state and fault currents of $2\ {\text{kA}}$ and $10\ {\text{kA}}$, respectively, presaturated core fault current limiter (PFCL) through connecting two series units rated $250\ {\text{kV}}$ each. It can replace the conventionally used PFCL in the form of a bulk CI (letters: CI) iron-core by a much smaller six CI iron-core units arranged on the six sides of a regular hexagon. The PFCL design and performance improvement are carried out through three-dimensional (3D) finite-element (FE) simulation using COMSOL Multiphysics. The time-varying fault inductance value significantly depends on the line coil generated magnetomotive force (mmf). The PFCL line coils are subdivided and wound by $500\ {\text{kV}}$ cross-linked polyethylene (XPLE) cables. The total high induced voltage across the presaturation coil is eliminated by subdividing it into subcoils orthogonally distributed around the iron core and differentially connected in series. A laboratory-scale PFCL is developed to validate FE simulation results of the time-varying current at different presaturation current, and a good agreement is found between both of them. The design capability can be extended by adding more CI-core units located on the sides of both regular octagonal and regular decagonal, or by increasing the design dimensions by an overall geometry scale factor. This modular topology gives substantial reduction in the iron-core volume (cost-effective design), superior performance, enhanced longevity, reliability, and flexibility in controllability and upgrading.