scope:

The information in this Guide is applicable to all forms of isolated-phase buses operating in alternating-current power systems. It is not meant to apply to other forms of open or enclosed buses, although some of the material will be useful in most bus applications. Familiarity with Standards applying to metal-enclosed buses is assumed and provisions of those Standards are indicated only when necessary for clarity in describing limiting conditions.

PURPOSE

This Guide is intended for general use in the application of isolated-phase buses. It will serve as a ready reference of pertinent material for those responsible for determining looses and evaluating equipment.

All conductors carrying electric current will produce power losses. This Guide covers methods for calculating conductor and enclosure losses at bus operating temperatures, including skin effect. In making power loss calculations, the I²R losses in the enclosure are considered. Means of determining such losses for various bus configurations are included. If the bus is forced-cooled, "the power requirements of the cooling equipment will be included in the total power loss.

For high-current installations, consideration should be given to the problem of induced magnetic heating and induced circulating current in nearby metallic members such as support beams and reinforcing rods. The Guide also contains references to assist in the estimation of heating effects of adjacent structural members. Such induced currents should be minimized to reduce extraneous losses. Methods of reducing eddy current and hysteresis losses and eliminating losses due to circulating currents are indicated.