Seismic Fragility of Representative High-Voltage Electrical Equipment Considering Joint Ground-Motion and Material Variability

Ground-motion variability and uncertain material properties affect seismic tensile demand in high-voltage equipment. This study examines idealized 550 kV circuit-breaker, current-transformer, and voltage-transformer configurations using finite-element models, joint parameter–record sampling, and elastic first-passage fragility analysis. Bidirectional linear modal responses are combined with fixed gravity stresses; the intensity measure is the geometric mean of horizontal component PGAs. Record metadata, response spectra, available numerical verification, and clustered statistical uncertainty are reported. For the circuit breaker, the lower porcelain post governs all 60 combinations; the fixed-strength fragility median and logarithmic dispersion are 0.528 g and 0.441. For the current transformer, incorporating sampled tensile strength gives a demand-model median of 0.859 g and dispersion of 0.320. For the voltage transformer, direct first-passage capacity medians are 0.144 g, 0.469 g, and 1.551 g from the lower to upper insulating section. Between-record differences account for 99.4% and 99.7% of the observed log-capacity sums of squares in the two transformer ensembles under the adopted 2% material variability. These are conditional elastic tensile-threshold estimates, with uncalibrated material statistics and incomplete device-specific experimental validation; they do not establish a general ranking of equipment types or predict electrical functionality.