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Definition of voltage ranges

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IEC voltage standards and recommendations

Three-phase four-wire or three-wire systems Nominal voltage (V)

Single-phase three-wire systems Nominal voltage (V)

50 Hz 60 Hz 60 Hz
- 120/208 120/240[d]
230[c] 240[c] -
230/400[a] 230/400[a] -
- 277/480 -
- 480 -
- 347/600 -
- 600 -
400/690[b] - -
1000 - -

[a]  The value of 230/400 V is the result of the evolution of 220/380 V and 240/415 V systems which has been completed in Europe and many other countries. However, 220/380 V and 240/415 V systems still exist.
[b]  The value of 400/690 V is the result of the evolution of 380/660 V systems which has been completed in Europe and many other countries. However, 380/660 V systems still exist.
[c]  The value of 200 V or 220 V is also used in some countries.
[d]  The values of 100/200 V are also used in some countries on 50 Hz or 60 Hz systems.
Note:
* the lower values in the first and second columns are voltages to neutral and the higher values are voltages between phases. When one value only is indicated, it refers to three-wire systems and specifies the voltage between phases. The lower value in the third column is the voltage to neutral and the higher value is the voltage between lines.
* voltages in excess of 230/400 V are intended for heavy industrial applications and large commercial premises.
* concerning supply voltage range, under normal operating conditions, the supply voltage should not differ from the nominal voltage of the system by more than ±10 %.

Fig. A1Standard voltages between 100 V and 1000 V (IEC 60038 Edition 7.0 2009-06)

Series I Series II
Highest voltage for equipment (kV) Nominal system voltage (kV) Highest voltage for equipment (kV) Nominal system voltage (kV)
3.6[b] 3.3[b] 3[b] 4.40[b] 4.16[b]
7.2[b] 6.6[b] 6[b] - -
12 11 10 - -
- - - 13.2[c] 12.47[c]
- - - 13.97[c] 13.2[c]
- - - 14.52[b] 13.8[b]
(17.5) - (15) - -
24 22 20 - -
- - - 26.4[c][e] 24.94[c][e]
36[d] 33[d] 30[d] - -
- - - 36.5[c] 34.5[c]
40.5[d] - 35[d] - -

[a]  These systems are generally three-wire systems, unless otherwise indicated. The values indicated are voltages between phases. The values indicated in parentheses should be considered as non-preferred values. It is recommended that these values should not be used for new systems to be constructed in future.
[b]  These values should not be used for new public distribution systems.
[c]  These systems are generally four-wire systems and the values indicated are voltages between phases. The voltage to neutral is equal to the indicated value divided by 1.73.
[d]  The unification of these values is under consideration.
[e]  The values of 22.9 kV for nominal voltage and 24.2 kV or 25.8 kV for highest voltage for equipment are also used in some countries.
Note 1: It is recommended that in any one country the ratio between two adjacent nominal voltages should be not less than two.
Note 2: In a normal system of Series I, the highest voltage and the lowest voltage do not differ by more than approximately ±10 % from the nominal voltage of the system. In a normal system of Series II, the highest voltage does not differ by more then +5 % and the lowest voltage by more than -10 % from the nominal voltage of the system.

Fig. A2AC 3 phases Standard voltages above 1 kV and not exceeding 35 kV (IEC 60038 Edition 7.0 2009)[a]