IEEE C37.81

Description / Abstract: This guide provides requirements and guidance for the seismic qualification of metal-enclosed power switchgear assemblies including switching, interrupting, control, instrumentation, metering, and protective and regulating devices mounted therein.

This guide may be used by equipment manufacturers to establish procedures that will yield data to substantiate performance or by equipment users to evaluate and verify performance of representative devices and assemblies as part of an overall qualification effort.

As used in this guide, the word switchgear shall mean metal-enclosed power switchgear assemblies with the requirements as defined in IEEE Std C37.20.1™, IEEE Std C37.20.2™, IEEE and Std C37.20.3™.^2,3,4 By definition, metal-enclosed power switchgear assemblies include metal-clad switchgear, metal-enclosed interrupter switchgear, and low-voltage power circuit breaker switchgear. This guide does not cover metalenclosed bus or control switchboards.

Metal-enclosed power switchgear assemblies fall into the category of complex devices as described in IEEE Std 344™. Therefore, basic seismic qualification is dependent on test data. Switchgear assemblies have many different types and arrangements of devices and components. It is neither practical nor necessary to test each unique configuration of devices and components, nor is it necessary to test a given configuration for every possible seismic environment. However, it is essential that each switchgear assembly used in Seismic Category I and Seismic Category II applications be seismically qualified for its environment, and Seismic Category I qualification must be based on data obtained by test. Analysis may be used in data reduction, reconciling response spectra, evaluation of changes and Seismic Category II qualification.

A method of combined test and analysis may also be used in justifying seismic qualification of equipment similar to the tested sample. A combination of testing and analysis may also be used to justify the seismic qualification of equipment with removable elements and drawout-mounted devices in various positions (connect, test, disconnect, and removed).

Devices, such as relays, instruments, circuit breakers, and control switches, are qualified for use on a switchgear assembly by demonstrating that their seismic withstand capabilities as determined by seismic tests equal or exceed the seismic environment of the location on the switchgear assembly where they will be mounted.

Four standard Generic Response Spectra (GRS) have been developed to cover the seismic requirements for most locations. The GRS have been developed as a composite of a number of Required Response Spectra (RRS) proposed for nuclear generating stations throughout the US, and cover approximately 75% of the locations sampled. The GRS establish standard seismic ratings, and any switchgear assembly that has been demonstrated by test to have met a rating will therefore be seismically qualified for any user application where the RRS is enveloped by the GRS.

If the standard GRS do not apply to a particular application, specific seismic information must be furnished by the user and used as the basis for qualification

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³The IEEE standards or products referred to in this clause are trademarks of the Institute of Electrical and Electronics Engineers, Inc.

⁴Information on references can be found in Clause 2.