Definition of voltage ranges
From Electrical Installation Guide
As per 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 | |
| - | 240 | - | |
| 230/400(1) | 277/480 | - | |
| 400/690 (1) | 480 | - | |
| - | 347/600 | - | |
| 1000 | 600 | - | |
Fig. A1: Standard voltages between 100 V and 1000 V (IEC 60038 Edition 6.2 2002-07)
(1) The nominal voltage of existing 220/380 V and 240/415 V systems shall evolve toward the recommended value of 230/400 V. The transition period should be as short as possible and should not exceed the year 2003. During this period, as a first step, the electricity supply authorities of countries having 220/380 V systems should bring the voltage within the range 230/400 V +6 %, -10 % and those of countries having 240/415 V systems should bring the voltage within the range 230/400 V +10 %, -6 %. At the end of this transition period, the tolerance of 230/400 V ± 10 % should have been achieved; after this the reduction of this range will be considered. All the above considerations apply also to the present 380/660 V value with respect to the recommended value 400/690 V.
| Series I | Series II | |||
| Highest voltage for equipment (kV) | Nominal system voltage (kV) | Highest voltage for equipment (kV) | Nominal system voltage (kV) | |
| 3.6 (1) | 3.3 (1) | 3 (1) | 4.40 (1) | 4.16 (1) |
| 7.2(1) | 6.6 (1) | 6 (1) | - | - |
| 12 | 11 | 10 | - | - |
| - | - | - | 13.2 (2) | 12.47 (2) |
| - | - | - | 13.97 (2) | 13.2 (2) |
| - | - | - | 14.52 (1) | 13.8 (1) |
| (17.5) | - | (15) | - | - |
| 24 | 22 | 20 | - | - |
| - | - | - | 26.4(2) | 24.94 (2) |
| 36 (3) | 33 (3) | - | - | - |
| - | - | - | 36.5 | 34.5 |
| 40.5(3) | - | 35(3) | - | - |
Fig. A2: Standard voltages above 1 kV and not exceeding 35 kV (IEC 60038 Edition 6.2 2002-07)
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.
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.
(1) These values should not be used for public distribution systems.
(2) These systems are generally four-wire systems.
(3) The unification of these values is under consideration.
