A database has been developed that documents the performance of substation equipment in 12 California earthquakes. The equipment in the database is owned by the Pacific Gas and Electric Company, the Los Angeles Department of Water and Power, Southern California Edison and the California Department of Water Resources. The majority of data relates to equipment operating at 220/230 kV and 500 kV. The database is organized into an Excel 5.0 spreadsheet with 68 data fields describing earthquake location, ground motion, site location and conditions, equipment characteristics, performance of equipment, failure mode, and restoration time. Each record represents a single piece of damaged equipment or several pieces of similar undamaged equipment.
Ground motions in the database are based on recordings if the site was instrumented. In other cases, ground motions are based on event-specific attenuation relationships developed by Somerville and Smith (1999).
The purpose of the database is to provide a basis for developing or improving equipment vulnerability functions. The probabilities of failure are calculated by dividing the number of damaged items by the total number of items of that type at each site. Using peak ground acceleration as the ground motion parameter, failure probabilities are compared with opinion-based fragility curves for a few selected equipment classes. Comparisons are somewhat crude in that the calculated failure probabilities do not include information about the mode of failure. The comparisons indicate that some of the existing fragility curves provide reasonable matches to the data and others should be modified to better reflect the data.
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