Hierarchical Sub-Modeling for Electromagnetic Performance Analysis of a 550 kV Mobile HGIS

The 550 kV mobile hybrid gas-insulated switchgear (HGIS) has severe difficulties for electromagnetic performance evaluations due to its highly integrated and compact structure. To address this issue, this paper proposes a hierarchical sub-modeling framework. A simplified global model of a 550 kV mobile HGIS retaining the complete main-circuit topology is first established for the macroscopic electrostatic screening of insulation weak zones. Then, high-precision sub-models of the circuit breaker and disconnector switch are then extracted for refined verification. By combining a differentiated meshing strategy with a two-step dynamic solution scheme, transient electric-field evolution of the HGIS is coupled with steady-state and short-circuit transient thermal–fluid simulations. The study reveals that the insulation weak points are explicitly classified into static-structural and dynamic-motion types and identifies that the dynamic closing is the governing condition for insulation verification in the HGIS. The work further shows role reversal of the SF6 gas between a steady-state overload current and limit short-circuit current condition. The proposed hierarchical modeling for the HGIS significantly reduces the simulation complexity while preserving accuracy, providing efficient analysis guidance and a quantitative basis for the performance validation and structural optimization of compact ultra-high-voltage switchgear.