The selection of busbar trunking systems is very straightforward, using the data provided by the manufacturer. Methods of installation, insulation materials, correction factors for grouping are not relevant parameters for this technology making the selection of busways much more straightforward than the sizing of a traditional distribution with cables. The cross section area of any given model has been determined by the manufacturer based on: The rated current, An ambient air temperature equal to 35 °C, 3 loaded conductors.
The rated current can be calculated taking account of: The layout, The current absorbed by the different loads connected along the trunking system.
A correction factor has to be applied for temperature higher than 35 °C. The correction factor applicable is provided by the busway manufacturer. As an example, for Schneider Electric medium and high power range (up to 4000 A) the correction factor is given in .
Correction factor
1
0.97
0.93
0.90
0.86
Where 3rd harmonic currents are circulating, the neutral conductor may be carrying a signiďŹ cant current and the corresponding additional power losses must be taken into account. represents the maximum admissible phase and neutral currents (per unit) in a high power busbar trunking system as functions of 3 rd harmonic level. For more information, see Chapter E - paragraph 2.3 "Harmonic currents in the selection of busbar trunking systems (busways)".
Schneider Electric - Electrical installation guide 2015