scope:

This design guide provides direction for the substation engineer in the design of air insulated substations. This guide provides users with information on typical bus arrangements including various criteria necessary to develop bus arrangement decisions. The guide is applicable to both rigid bus and strain bus designs for outdoor and indoor, air-insulated, alternating current substations. This guide includes a method to calculate ampacity for electrical bus and ampacity tables for typical bus types and sizes. This guide also provides design criteria and a method to calculate electromechanical forces on insulators and bus resulting from gravity, wind, ice, short circuit forces, and thermal expansion. This guide does not consider the following:

a) The electrical criteria for the selection of insulators (see IEEE Std 1313.2 ^TM)

b) The seismic forces to which the substation may be subjected (see IEEE Std 693^TM and IEEE Std 1527^TM)

c) The design of mounting structures (see ASCE 113)

d) Design considerations for contaminated environments (see IEEE Std 1313.2 ^TM)

e) Installation methods

f) Design of direct current bus

g) Fault loads other than between conductors such as in the presence of other magnetic fields (e.g. air core reactors)

Purpose

Substation rigid and strain bus structure design involves electrical, mechanical, and structural considerations. It is the purpose of this guide to integrate these considerations into one document. Special considerations are given to fault current force calculations.