scope:

This publication applies to

- AC transmission, distribution and utilization systems and equipment for use in such systems with standard frequencies 50 Hz and 60 Hz having a nominal voltage above 100 V;

- AC and DC traction systems;

- AC and DC equipment having nominal voltages below 120 V AC or below 750 V DC, the AC voltages being intended (but not exclusively) for 50 Hz and 60 Hz applications; such equipment covers batteries (from primary or secondary cells), other power supply devices (AC or DC), electrical equipment (including industrial and communication), and appliances.

This publication does not apply to voltages representing or transmitting signals or measured values.

This publication does not apply to standard voltages of components and parts used within electrical devices or items of equipment.

This publication has the status of a horizontal standard in accordance with IEC Guide 108. As such, this publication specifies standard voltage values which are intended to serve

− as preferential values for the nominal voltage of electrical supply and utilization systems, and

− as maximum, nominal and minimum reference values for both equipment and power supply in both electricity supply and utilization systems so that product and power system committees can co-ordinate their documents.

NOTE 1 Two main reasons have led to the values specified in this standard:

The values of nominal voltage (or highest voltage for equipment) specified in this standard are mainly based on the historical development of electrical supply systems throughout the world, since these values turned out to be the most common ones, and have achieved worldwide recognition;

The voltage ranges mentioned in this standard have been recognized to be the most appropriate ones as a basis for design and testing of electrical equipment and systems.

NOTE 2 It is nevertheless the task of system and product standards to define appropriate testing values, testing conditions and acceptance criteria.

NOTE 3 National Committees and individual systems can set values that differ from, but still comply with, the reference values in this document provided the values they set lie between the highest voltage for equipment and the lowest supply or utilization voltages in this document. Such variations can be required due to legacy or rating issues.

NOTE 4 To comply with this documentneither the lowest supply or utilization voltage can be lower than the lowest voltage for equipment.

NOTE 5 Some National committees set different nominal values for supply and utilization.