A Key to Community Earthquake Resilience Is Neglected

The disruption of power systems on community resilience is particularly important because many other lifelines and community functions depend on commercial power. Power systems have been design to be fault tolerant by incorporating a high degree of redundancy in substations and the network. Unlike most power system elements, a damaged transformer cannot be bypassed to restore service and the restoration of transformer bushings, their most vulnerable component, require lengthy restoration times. Limited shake-table test data from a transformer tank indicates that bushings are sensitive to resonance on resonance damage, which the current standard does not assess. This paper describes the need for modifying the standard to address this deficiency. There is a need to have the standard require a dynamic analysis of the transformer-bushing system to assess this vulnerability and assure that mitigation measures are implemented. Testing of fully dressed transformers is needed to support these changes.