International Standard IEC 60038, IEC standard voltages, defines a set of standard voltages for use in low voltage and high voltage AC and DC electricity supply systems.

Low voltage

Where two voltages are given below separated by "/", the first is the root-mean-square voltage between a phase and the neutral connector, whereas the second is the corresponding root-mean-square voltage between two phases (exception: the category shown below called "One Phase", where 240 V is the root-mean-square voltage between the two legs of a split phase). The three-phase voltages are for use in either four-wire (with neutral) or three-wire (without neutral) systems.

Three-phase 50 Hz

• 230 V / 400 V (formerly 220/380 V)
• 400 V / 690 V (formerly 380/660 V)
• 1000 V phase to phase (3 wire)

Suppliers using 220 V / 380 V or 240 V / 415 V systems were expected by the standard to migrate to the recommended value of 230 V / 400 V by the year 2003. This migration has already been largely completed, at least within the European Union.

Voltage conversion schedule

Three-phase 60 Hz

• 120 V / 208 V
• 240 V
• 230 V / 400 V
• 277 V / 480 V
• 480 V
• 347 V / 600 V
• 600 V / 1000 V

One-phase, three-wire 60 Hz (American split-phase)

• 120 V / 240 V

Table 3 1 kV to 35 kV

Table 3 of IEC 60038 lists nominal voltages above 1 kV and not exceeding 35 kV. There are two series, one from 3 kV up to 35 kV

Table 4 35 kV - 230 kV

Table 4 shows nominal voltages above 35 kV and not exceeding 230 kV.

Table 5 245 - 1,200 kV

Table 5 is systematically different, as the highest voltage for equipment is the characteristic value exceeding 245 kV. The enumeration begins at 300 kV and ends with 1200 kV.