Seismic Design of Substations—IEEE Standard 693 Gets a Major Update

Over the past several years, large magnitude earthquakes have inflicted significant damage on lifeline infrastructure, including electric power systems. These events serve as reminders of the importance of implementing good seismic design practices in order to deploy resilient systems that sustain limited damage and can be restored within reasonable time frames. IEEE Std. 693, Recommended Practice for the Seismic Design of Substations is the standard of choice for the seismic qualification and design of substation equipment and their supports. At the time of this writing, the new edition of the standard was in the final stages of approval. This paper discusses basic concepts of IEEE Std. 693 and describes the most significant changes expected in the approved version. These changes include guidance for the use of seismic protective systems (e.g., base isolators and dampers), qualification of DC equipment, insulator seismic strength criteria, the explicit consideration of conductor load effects in equipment qualification procedures, guidance for nonlinear dynamic analysis of equipment/supports, revised procedures for developing input time histories for testing and analysis, and changes to transformer bushing shake table test protocols. Improved consistency and coordination with IEEE Std. 1527 (Design of Bus Work in Seismically Active Areas) and ASCE Manual of Practice 113 (Design of Substation Structures) have also been built into the revised IEEE Std. 693.