3. Equipment selection and layout

3.1 Choice of equipment

The components (equipment, sub-assemblies) must comply with the corresponding standards and be suitable for their particular application in terms of the external appearance of the assembly (e.g. open or enclosed), and their electrical and mechanical characteristics.

Some of these characteristics may be affected by their incorporation into an assembly; this is notably the case for fuses, contactors and switches, which may be subject to derating (reduction in their rated current), taking into account the conditions of proximity with other equipment and the internal temperature of the assembly in operation.

The maximum permissible currents of certain devices must also be coordinated with the characteristics of upstream...