Conditional Root-Stress Exceedance of a 220 kV Disconnect Switch Under Dynamic Slurry–Boulder Debris-Flow Loading

Distributed slurry pressure and local boulder pulses can induce transient stresses in outdoor disconnect switches. This study evaluates conditional root-stress exceedance in an idealized 220 kV disconnect-switch model with prescribed geometry, tied connections, fixed bases, equivalent linear-elastic materials, and separately imposed load histories. Four fixed screening levels of 165, 235, 282, and 375 MPa were considered. The original coarse-mesh (N1) archive contains 213 distinct loading cases, including 100 combined-load cases at four prescribed heights and matched component, height, and load-model checks. The primary demand is the maximum von Mises invariant of the tensor averaged at the original monitored root point. The same 100 combined-load cases were evaluated on the G3H3 and G4H4 meshes in a paired comparison. From G3H3 to G4H4, the median absolute point-demand change was 4.87%, the maximum relative change in the fitted median exceedance velocity was 2.45%, and the largest same-velocity exceedance-probability difference was 21.85 percentage points. The primary curves exceeded the proposed numerical sensitivity targets. The point demands increased by 23.43–27.72% from N1 to G4H4, demonstrating the mesh dependence of the original results. A fixed-volume tensor response was more stable, but remains supplementary and does not validate the point metric. The pressure-redistribution checks used two selected scenarios, and the component comparisons at the two greater heights used eight matched cases per height. These checks illustrate numerical sensitivity and case-specific differences within the N1 reference model; they do not constitute a comprehensive uncertainty analysis or establish physical failure probabilities. This exploratory numerical case study quantifies stress-screening sensitivity within the adopted idealization rather than reconstructing a specific installed unit. No mesh-independent local peak, calibrated physical damage state, or site-specific failure probability is established.