Damage to devices installed in electrical substations, which have shown vulnerability during strong earthquakes in recent decades, can jeopardize energy supply during and after an earthquake emergency. Within the scope of seismic risk assessment of electrical networks, defining the fragility functions of electrical equipment is crucial.

However, in current literature, the availability of fragility models for specific components of electrical substations, including measurement transformers, is relatively limited. This gap motivated experimental and numerical research. Two voltage transformers and two current transformers, operating at different system voltage levels (respectively in the HV and EHV ranges), underwent shake table tests. Experimental results were used to calibrate corresponding 3D numerical models developed in OpenSees. Numerous nonlinear dynamic analyses conducted using multi-stripe analysis (MSA) resulted in 16 fragility curves for the four transformers under two different conditions (with and without base support), considering two types of soil.

Based on the derived curves, it is predicted that one of the voltage transformers will sustain minor or negligible damage during seismic shaking due to its high resonance frequencies (and thus stiffness), while the other three devices may experience moderate damage under medium-strong shaking; however, their seismic risk is effectively mitigated by the base support used. Comparison with models available in the literature provided valuable reassurance regarding the adequacy of the methodology used and the reliability of the derived fragility curves.