About Delta-Unibus

 


Isolated phase bus and associated equipment is manufactured to ANSI Standard C37.20: Switchgear Assemblies including metal Enclosed Bus. Section 8 of this standard deals specifically with metal enclosed buses. Metal enclosed buses have three basic types of construction, namely non-segregated phase, segregated phase and isolated phase. These are defined as follows:
 
Standards and Definitions
Forced Air Cooling
Ratings
Dimensional Data

 
Metal Enclosed Bus (ANSI definition 20-2.1.4)
An Assembly of rigid conductors with associated connections, joints and insulating supports with a grounded metal enclosure.

Non-Segregated Phase Bus (ANSI definition 20-2.1.4.1)
One in which all phase conductors are in a common metal enclosure without barriers between phases. (When associated with metal-clad switchgear the primary bus conductors and connections are covered with insulating material throughout).

Segregated Phase Bus (ANSI definition 20-2.1.4.2)
One in which all phase conductors are in a common metal enclosure, but are segregated by metal barriers between phases.

Isolated Phase Bus (ANSI definition 20-2.1.4.3)
One in which each phase conductor is enclosed by an individual metal housing separated from adjacent conductor housings by an air space. (The bus may be self-cooled or force-cooled by means of circulating air, gas or liquid).

This site specifically describes the application of isolated phase bus as main generator leads in power plants and in circuits where a high degree of reliability is required.
Isolated phase bus is also governed by a related ANSI Standard C37.23: Guide for Calculating Losses in Isolated Phase Bus. This standard also recognizes two design variations of isolated phase bus, namely, non-continuous enclosure design and continuous enclosure design or no-flux design.