IEEE 693. The IEEE 693: Recommended Practice for Seismic Design of Substations. is a Institute of Electrical and Electronics Engineers standard. This standard is recognized also by American National Standards Institute, and is used mainly in the American Continent.  

The goal of the standard is to provide a single set of rules and regulations that cover the seismic design of both new and existing electrical substations, hence leading to standardization. The standard provides the minimum requirements that the design of an electrical substation (except nuclear power plants) must adhere to. The norm includes the design of circuit breakers, transformers, disconnect and grounding switches, instrument transformers, circuit switches, surge arresters, and other equipment.

Contents 
The norm contains the 8 chapters named below:
 Overview
 Normative references
 Definitions, acronyms, and abbreviations
 Instructions
 General
 Specifying this recommended practice in user's specification
 Standardization of criteria
 Selection of qualification level
 Witnessing of shake-table testing
 Optional qualification methods
 Qualifying equipment by group
 Inherently acceptable equipment
 Shake-table facilities
 Equipment too large to be tested in its in-service configuration
 Report templates
 Installation considerations
 General
 Equipment assembly
 Site response characteristics
 Soil-structure interaction
 Support structures
 Base isolation
 Suspended equipment
 Anchorage
 Conductor induced loading
 Interconnections with adjacent equipment
 Observed component displacements
 Decoupling equipment through flexible bus-work
 Conductor installation
 Short-circuit loads
 Wind and ice loads
 Qualification methods: an overview
 General
 Analysis methods
 Static analysis
 Static coefficient analysis
 Response spectrum dynamic analysis
 Time history dynamic analysis
 Testing methods
 Special test cases
 Qualification method for specific equipment
 Functionality of equipment
 Qualification by seismic experience data
 Response spectra
 Damping
 Design considerations
 Structural supports, excluding foundations
 Foundation analysis
 Station service
 Emergency power systems
 Telecommunication quipment
 Seismic performance criteria for electrical substation equipment
 Introduction
 Objective
 Seismic qualification levels
 High seismic level
 Moderate seismic level
 Low seismic level
 Projected performance
 Performance levels
 High 
 Moderate
 Low
 Seismic qualification
 High and moderate seismic qualification levels
 Low seismic qualification level
 Selecting the seismic level for seismic qualification
The norm specifies 3 seismic qualification levels (high, medium, low). The Zero Period Acceleration (ZPA) (a.k.a. Peak Ground Acceleration) for the high and the medium qualifications levels are set to be 0.5g and 0.25 respectively (no calculation is required for equipment with "low" qualification), where g stands for acceleration due to gravity. The Peak Acceleration (i.e. the peak of the Response Spectrum) at 2% damping is lower than 1.65g and 0.85g for high and medium qualification respectively, with the cutoff frequency defined as 33Hz.    

The qualification is allowed through one of the following:

 Shake Table Testing
 Calculations
 Experience

The norm suggests that most equipment in the same area be given the same qualification level (for interchangeability and redundancy).

Annex 
There are a total of 22 annexes in the standard, 19 of which are normative, and the other 3 are informative.

History 
The first version of the standard was released in 1997, with a revised version released in 2005 and later in 2018.

References 

Institute of Electrical and Electronics Engineers