| IEC voltage range | AC | DC | defining risk |
|---|---|---|---|
| High voltage (supply system) | > 1000 Vrms | > 1500 V | electrical arcing |
| Low voltage (supply system) | 25–1000 Vrms | 60–1500 V | electrical shock |
| Extra-low voltage (supply system) | < 25 Vrms | < 60 V | low risk |
International Standard IEC 60038 defines a set of standard voltages for use in low voltage and high voltage AC electricity supply systems.
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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.
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.