IEEE Recommended Practice for Seismic Design of Substations

Fault line where earthquakes may happen and safety guidelines outlined in IEEE 693

IEEE 693-2018 is the IEEE Recommended Practice For Seismic Design Of Substations.

In ancient Greece, an earthquake was said to occur when Poseidon was in a bad mood. Enraged, the god of the sea would strike the ground with his trident, bringing forth a slew of calamities. Throughout history, other peoples across the globe have attributed seismic activity to similar actions of the divine. Even today, ground shaking and surface faulting driven by mantle convection seem to carry a preternaturally-extreme power.

In society, there is a need and demand for structures to withstand the tremendous forces that seismic activity can inflict, both for the integrity of those buildings and the safety of their occupants. For electrical substations, which act as part of the electrical generation, transmission, and distribution system, the sudden release of energy from rupture of geological faults in the earth’s crust should be addressed with unique seismic considerations.

As discussed in IEEE 693-2018, substations are unique in that they need to maintain functionality, are composed of unique materials (such as porcelain and composites), have relatively low damping and high frequency dynamic characteristics, and maintain the interconnection of equipment via electrical conductors. While earthquake engineering for substations was initially based on practices used for conventional structures, these idiosyncrasies, paired with the demand of electrical service in any post-earthquake environment, warranted a specific focus.

IEEE 693-2018 considers these concerns for substations, as well as numerous associated factors. The recommended practice addresses buildings, foundations, station service, and telecommunication equipment, in addition to various subjects in its annexes, such as circuit breakers, transformers, disconnect switches, and capacitors.

Overall, IEEE 693-2018 provides minimum guidelines for the seismic design of substations and the seismic qualification of equipment, with an emphasis on electrical equipment and its anchorage. For the ease of the user, the standard features a section on the document’s instructions.

 IEEE 693-2018 is a revision of IEEE 693-2005. The current edition was changed in the following ways:

  • “Shake-table test requirements” for qualification of bushings were modified.
  • Conductor seismic loading effects are now explicitly included as part of the qualification of certain equipment.
  • Time history shake-table testing at the Performance Level is now needed for most equipment that need to be qualified by the time history test method.
  • Seismic loads for the design of anchorages of inherently acceptable equipment were increased.

IEEE 693-2018: IEEE Recommended Practice For Seismic Design Of Substations is available on the ANSI Webstore.

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