Low-voltage consumers
The most-common LV supplies are within the range 120 V single phase to 240/415 V 3-phase 4-wires.
Loads up to 250 kVA can be supplied at LV, but power-supply organizations generally propose a MV service at load levels for which their LV networks are marginally adequate.
An international voltage standard for 3-phase 4-wire LV systems is recommended by the IEC 60038 to be 230/400 V
In Europe, the transition period on the voltage tolerance to “230V/400V + 10% / 10%” has been extended for another 5 years up to the year 2008.
Low-voltage consumers are, by definition, those consumers whose loads can be satisfactorily supplied from the low-voltage system in their locality.
The voltage of the local LV network may be 120/208 V or 240/415 V, i.e. the lower or upper extremes of the most common 3-phase levels in general use, or at some intermediate level, as shown in Figure C1.
An international voltage standard for 3-phase 4-wire LV systems is recommended by the IEC 60038 to be 230/400 V.
Loads up to 250 kVA can be supplied at LV, but power-supply organizations generally propose a MV service at load levels for which their LV networks are marginally adequate.
| Country | Frequency & tolerance (Hz & %) |
Domestic (V) | Commercial (V) | Industrial (V) |
|---|---|---|---|---|
| Afghanistan | 50 220 (k) |
380/220 (a) | 380/220 (a) | 380/220 (a) |
| Algeria | 50 ± 1.5 | 220/127 (e) 220 (k) |
380/220 (a) 220/127 (a) |
10,000 5,500 6,600 380/220 (a) |
| Angola | 50 | 380/220 (a) 220 (k) |
380/220 (a) | 380/220 (a) |
| Antigua and Barbuda | 60 | 240 (k) 120 (k) |
400/230 (a) 120/208 (a) |
400/230 (a) 120/208 (a) |
| Argentina | 50 ± 2 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
|
| Armenia | 50 ± 5 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Australia | 50 ± 0.1 | 415/240 (a) 240 (k) |
415/240 (a) 440/250 (a) 440 (m) |
22,000 11,000 6,600 415/240 440/250 |
| Austria | 50 ± 0.1 | 230 (k) | 380/230 (a) (b) 230 (k) |
5,000 380/220 (a) |
| Azerbaijan | 50 ± 0.1 | 208/120 (a) 240/120 (k) |
208/120 (a) 240/120 (k) |
|
| Bahrain | 50 ± 0.1 | 415/240 (a) 240 (k) |
415/240 (a) 240 (k) |
11,000 415/240 (a) 240 (k) |
| Bangladesh | 50 ± 2 | 410/220 (a) 220 (k) |
410/220 (a) | 11,000 410/220 (a) |
| Barbados | 50 ± 6 | 230/115 (j) 115 (k) |
230/115 (j) 200/115 (a) 220/115 (a) |
230/400 (g) 230/155 (j) |
| Belarus | 50 | 380/220 (a) 220 (k) 220/127 (a) 127 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Belgium | 50 ± 5 | 230 (k) 230 (a) 3N, 400 |
230 (k) 230 (a) 3N, 400 |
6,600 10,000 11,000 15,000 |
| Bolivia | 50 ± 0.5 | 230 (k) | 400/230 (a) 230 (k) |
400/230 (a) |
| Botswana | 50 ± 3 | 220 (k) | 380/220 (a) | 380/220 (a) |
| Brazil | 60 ± 3 | 220 (k,a) 127 (k,a) |
220/380 (a) 127/220 (a) |
69,000 23,200 13,800 11,200 220/380 (a) 127/220 (a) |
| Brunei | 50 ± 2 | 230 | 230 | 11,000 68,000 |
| Bulgaria | 50 ± 0.1 | 220 | 220/240 | 1,000 690 380 |
| Cambodia | 50 ± 1 | 220 (k) | 220/300 | 220/380 |
| Cameroon | 50 ± 1 | 220/260 (k) | 220/260 (k) | 220/380 (a) |
| Canada | 60 ± 0.02 | 120/240 (j) | 347/600 (a) 480 (f) 240 (f) 120/240 (j) 120/208 (a) |
7,200/12,500 347/600 (a) 120/208 600 (f) 480 (f) 240 (f) |
| Cape Verde | 220 | 220 | 380/400 | |
| Chad | 50 ± 1 | 220 (k) | 220 (k) | 380/220 (a) |
| Chile | 50 ± 1 | 220 (k) | 380/220 (a) | 380/220 (a) |
| China | 50 ± 0.5 | 220 (k) | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
| Colombia | 60 ± 1 | 120/240 (g) 120 (k) |
120/240 (g) 120 (k) |
13,200 120/240 (g) |
| Congo | 50 | 220 (k) | 240/120 (j) 120 (k) |
380/220 (a) |
| Croatia | 50 | 400/230 (a) 230 (k) |
400/230 (a) 230 (k) |
400/230 (a) |
| Cyprus | 50 ± 0.1 | 240 (k) | 415/240 | 11,000 415/240 |
| Czech Republic | 50 ± 1 | 230 | 500 230/400 |
400,000 220,000 110,000 35,000 22,000 10,000 6,000 3,000 |
| Denmark | 50 ± 1 | 400/230 (a) | 400/230 (a) | 400/230 (a) |
| Djibouti | 50 | 400/230 (a) | 400/230 (a) | |
| Dominica | 50 | 230 (k) | 400/230 (a) | 400/230 (a) |
| Egypt | 50 ± 0.5 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
66,000 33,000 20,000 11,000 6,600 380/220 (a) |
| Estonia | 50 ± 1 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Ethiopia | 50 ± 2.5 | 220 (k) | 380/231 (a) | 15 000 380/231 (a) |
| Falkland Islands | 50 ± 3 | 230 (k) | 415/230 (a) | 415/230 (a) |
| Fidji Islands | 50 ± 2 | 415/240 (a) 240 (k) |
415/240 (a) 240 (k) |
11,000 415/240 (a) |
| Finland | 50 ± 0.1 | 230 (k) | 400/230 (a) | 690/400 (a) 400/230 (a) |
| France | 50 ± 1 | 400/230 (a) 230 (a) |
400/230 690/400 590/100 |
20,000 10,000 230/400 |
| Gambia | 50 | 220 (k) | 220/380 | 380 |
| Georgia | 50 ± 0.5 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Germany | 50 ± 0.3 | 400/230 (a) 230 (k) |
400/230 (a) 230 (k) |
20,000 10,000 6,000 690/400 400/230 |
| Ghana | 50 ± 5 | 220/240 | 220/240 | 415/240 (a) |
| Gibraltar | 50 ± 1 | 415/240 (a) | 415/240 (a) | 415/240 (a) |
| Greece | 50 | 220 (k) 230 |
6,000 380/220 (a) |
22,000 20,000 15,000 6,600 |
| Granada | 50 | 230 (k) | 400/230 (a) | 400/230 (a) |
| Hong Kong | 50 ± 2 | 220 (k) | 380/220 (a) 220 (k) |
11,000 386/220 (a) |
| Hungary | 50 ± 5 | 220 | 220 | 220/380 |
| Iceland | 50 ± 0.1 | 230 | 230/400 | 230/400 |
| India | 50 ± 1.5 | 440/250 (a) 230 (k) |
440/250 (a) 230 (k) |
11,000 400/230 (a) 440/250 (a) |
| Indonesia | 50 ± 2 | 220 (k) | 380/220 (a) | 150,000 20,000 380/220 (a) |
| Iran | 50 ± 5 | 220 (k) | 380/220 (a) | 20,000 11,000 400/231 (a) 380/220 (a) |
| Iraq | 50 | 220 (k) | 380/220 (a) | 11,000 6,600 3,000 380/220 (a) |
| Ireland | 50 ± 2 | 230 (k) | 400/230 (a) | 20,000 10,000 400/230 (a) |
| Israel | 50 ± 0.2 | 400/230 (a) 230 (k) |
400/230 (a) 230 (k) |
22,000 12,600 6,300 400/230 (a) |
| Italy | 50 ± 0.4 | 400/230 (a) 230 (k) |
400/230 (a) | 20,000 15,000 10,000 400/230 (a) |
| Jamaica | 50 ± 1 | 220/110 (g) (j) | 220/110 (g) (j) | 4,000 2,300 220/110 (g) |
| Japan (east) | + 0.1 - 0.3 |
200/100 (h) | 200/100 (h) (up to 50 kW) |
140,000 60,000 20,000 6,000 200/100 (h) |
| Jordan | 50 | 380/220 (a) 400/230 (k) |
380/220 (a) | 400 (a) |
| Kazakhstan | 50 | 380/220 (a) 220 (k) 220/127 (a) 127 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Kenya | 50 | 240 (k) | 415/240 (a) | 415/240 (a) |
| Kirghizia | 50 | 380/220 (a) 220 (k) 220/127 (a) 127 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Korea (North) | 60 +0, -5 | 220 (k) | 220/380 (a) | 13,600 6,800 |
| Korea (South) | 60 | 100 (k) | 100/200 (j) | |
| Kuwait | 50 ± 3 | 240 (k) | 415/240 (a) | 415/240 (a) |
| Laos | 50 ± 8 | 380/220 (a) | 380/220 (a) | 380/220 (a) |
| Lesotho | 220 (k) | 380/220 (a) | 380/220 (a) | |
| Latvia | 50 ± 0.4 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Lebanon | 50 | 220 (k) | 380/220 (a) | 380/220 (a) |
| Libya | 50 | 230 (k) 127 (k) |
400/230 (a) 220/127 (a) 230 (k) 127 (k) |
400/230 (a) 220/127 (a) |
| Lithuania | 50 ± 0.5 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Luxembourg | 50 ± 0.5 | 380/220 (a) | 380/220 (a) | 20,000 15,000 5,000 |
| Macedonia | 50 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
10,000 6,600 380/220 (a) |
| Madagascar | 50 | 220/110 (k) | 380/220 (a) | 35,000 5,000 380/220 |
| Malaysia | 50 ± 1 | 240 (k) 415 (a) |
415/240 (a) | 415/240 (a) |
| Malawi | 50 ± 2.5 | 230 (k) | 400 (a) 230 (k) |
400 (a) |
| Mali | 50 | 220 (k) 127 (k) |
380/220 (a) 220/127 (a) 220 (k) 127 (k) |
380/220 (a) 220/127 (a) |
| Malta | 50 ± 2 | 240 (k) | 415/240 (a) | 415/240 (a) |
| Martinique | 50 | 127 (k) | 220/127 (a) 127 (k) |
220/127 (a) |
| Mauritania | 50 ± 1 | 230 (k) | 400/230 (a) | 400/230 (a) |
| Mexico | 60 ± 0.2 | 127/220 (a) 120/240 (j) |
127/220 (a) 120/240 (j) |
4,160 13,800 23,000 34,500 277/480 (a) 127/220 (b) |
| Moldavia | 50 | 380/220 (a) 220 (k) 220/127 (a) 127 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Morocco | 50 ± 5 | 380/220 (a) | 380/220 (a) | 225,000 |
| 220/110 (a) | 150,000 60,000 22,000 20,000 | |||
| Mozambique | 50 | 380/220 (a) | 380/220 (a) | 6,000 10,000 |
| Nepal | 50 ± 1 | 220 (k) | 440/220 (a) 220 (k) |
11,000 440/220 (a) |
| Netherlands | 50 ± 0.4 | 230/400 (a) 230 (k) |
230/400 (a) | 25,000 20,000 12,000 10,000 230/400 |
| New Zealand | 50 ± 1.5 | 400/230 (e) (a) 230 (k) 460/230 (e) |
400/230 (e) (a) 230 (k) |
11,000 400/230 (a) |
| Niger | 50 ± 1 | 230 (k) | 380/220 (a) | 15,000 380/220 (a) |
| Nigeria | 50 ± 1 | 230 (k) 220 (k) |
400/230 (a) 380/220 (a) |
15,000 11,000 400/230 (a) 380/220 (a) |
| Norway | 50 ± 2 | 230/400 | 230/400 | 230/400 690 |
| Oman | 50 | 240 (k) | 415/240 (a) 240 (k) |
415/240 (a) |
| Pakistan | 50 | 230 (k) | 400/230 (a) 230 (k) |
400/230 (a) |
| Papua New Guinea | 50 ± 2 | 240 (k) | 415/240 (a) 240 (k) |
22,000 11,000 415/240 (a) |
| Paraguay | 50 ± 0.5 | 220 (k) | 380/220 (a) 220 (k) |
22,000 380/220 (a) |
| Philippines (Rep of the) | 60 ± 0.16 | 110/220 (j) | 13,800 4,160 2,400 110/220 (h) |
13,800 4,160 2,400 440 (b) 110/220 (h) |
| Poland | 50 ± 0.1 | 230 (k) | 400/230 (a) | 1,000 690/400 400/230 (a) |
| Portugal | 50 ± 1 | 380/220 (a) 220 (k) |
15,000 5,000 380/220 (a) 220 (k) |
15,000 5,000 380/220 (a) |
| Qatar | 50 ± 0.1 | 415/240 (k) | 415/240 (a) | 11,000 415/240 (a) |
| Romania | 50 ± 0.5 | 220 (k) 220/380 (a) |
220/380 (a) | 20,000 10,000 6,000 220/380 (a) |
| Russia | 50 ± 0.2 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Rwanda | 50 ± 1 | 220 (k) | 380/220 (a) | 15,000 6,600 380/220 (a) |
| Saint Lucia | 50 ± 3 | 240 (k) | 415/240 (a) | 11,000 415/240 (a) |
| Samoa | 400/230 | |||
| San Marino | 50 ± 1 | 230/220 | 380 | 15,000 380 |
| Saudi Arabia | 60 | 220/127 (a) | 220/127 (a) 380/220 (a) |
11,000 7,200 380/220 (a) |
| The Solomon Islands | 50 ± 2 | 240 | 415/240 | 415/240 |
| Senegal | 50 ± 5 | 220 (a) 127 (k) |
380/220 (a) 220/127 (k) |
90,000 30,000 6,600 |
| Serbia and Montenegro | 50 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
10,000 6,600 380/220 (a) |
| Seychelles | 50 ± 1 | 400/230 (a) | 400/230 (a) | 11,000 400/230 (a) |
| Sierra Leone | 50 ± 5 | 230 (k) | 400/230 (a) 230 (k) |
11,000 400 |
| Singapore | 50 | 400/230 (a) 230 (k) |
400/230 (a) | 22,000 6,600 400/230 (a) |
| Slovakia | 50 ± 0.5 | 230 | 230 | 230/400 |
| Slovenia | 50 ± 0.1 | 220 (k) | 380/220 (a) | 10,000 6,600 380/220 (a) |
| Somalia | 50 | 230 (k) 220 (k) 110 (k) |
440/220 (j) 220/110 (j) 230 (k) |
440/220 (g) 220/110 (g) |
| South Africa | 50 ± 2.5 | 433/250 (a) 400/230 (a) 380/220 (a) 220 (k) |
11,000 6,600 3,300 433/250 (a) 400/230 (a) 380/220 (a) |
11,000 6,600 3,300 500 (b) 380/220 (a) |
| Spain | 50 ± 3 | 380/220 (a) (e) 220 (k) 220/127 (a) 127 (k) |
380/220 (a) 220/127 (a) (e) |
15,000 11,000 380/220 (a) |
| Sri Lanka | 50 ± 2 | 230 (k) | 400/230 (a) 230 (k) |
11,000 400/230 (a) |
| Sudan | 50 | 240 (k) | 415/240 (a) 240 (k) |
415/240 (a) |
| Swaziland | 50 ± 2.5 | 230 (k) | 400/230 (a) 230 (k) |
11,000 400/230 (a) |
| Sweden | 50 ± 0.5 | 400/230 (a) 230 (k) |
400/230 (a) 230 (k) |
6,000 400/230 (a) |
| Switzerland | 50 ± 2 | 400/230 (a) | 400/230 (a) | 20,000 10,000 3,000 1,000 690/500 |
| Syria | 50 | 220 (k) 115 (k) |
380/220 (a) 220 (k) 200/115 (a) |
380/220 (a) |
| Tadzhikistan | 50 | 380/220 (a) 220 (k) 220/127 (a) 127 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Tanzania | 50 | 400/230 (a) | 400/230 (a) | 11,000 400/230 (a) |
| Thailand | 50 | 220 (k) | 380/220 (a) 220 (k) |
380/220 (a) |
| Togo | 50 | 220 (k) | 380/220 (a) | 20,000 5,500 380/220 (a) |
| Tunisia | 50 ± 2 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
30,000 15,000 |
| 10,000 380/220 (a) | ||||
| Turkmenistan | 50 | 380/220 (a) 220 (k) 220/127 (a) 127 (k) |
380/220 (a) 220 (k) |
380/220 (a) |
| Turkey | 50 ± 1 | 380/220 (a) | 380/220 (a) | 15,000 6,300 380/220 (a) |
| Uganda | + 0.1 | 240 (k) | 415/240 (a) | 11,000 415/240 (a) |
| Ukraine | + 0.2 / - 1.5 | 380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
380/220 (a) 220 (k) |
| United Arab Emirates | 50 ± 1 | 220 (k) | 415/240 (a) 380/220 (a) 220 (k) |
6,600 415/210 (a) 380/220 (a) |
| United Kingdom (except Northern Ireland) |
50 ± 1 | 230 (k) | 400/230 (a) | 22,000 11,000 6,600 3,300 400/230 (a) |
| United Kingdom (Including Northern Ireland) |
50 ± 0.4 | 230 (k) 220 (k) |
400/230 (a) 380/220 (a) |
400/230 (a) 380/220 (a) |
| United States of America Charlotte (North Carolina) |
60 ± 0.06 | 120/240 (j) 120/208 (a) |
265/460 (a) 120/240 (j) 120/208 (a) |
14,400 7,200 2,400 575 (f) 460 (f) 240 (f) 265/460 (a) 120/240 (j) 120/208 (a) |
| United States of America Detroit (Michigan) |
60 ± 0.2 | 120/240 (j) 120/208 (a) |
480 (f) 120/240 (h) 120/208 (a) |
13,200 4,800 4,160 480 (f) 120/240 (h) 120/208 (a) |
| United States of America Los Angeles (California) |
60 ± 0.2 | 120/240 (j) | 4,800 120/240 (g) |
4,800 120/240 (g) |
| United States of America Miami (Florida) |
60 ± 0.3 | 120/240 (j) 120/208 (a) |
120/240 (j) 120/240 (h) 120/208 (a) |
13,200 2,400 480/277 (a) 120/240 (h) |
| United States of America New York (New York) |
60 | 120/240 (j) 120/208 (a) |
120/240 (j) 120/208 (a) 240 (f) |
12,470 4,160 277/480 (a) 480 (f) |
| United States of America Pittsburg (Pennsylvania) |
60 ± 0.03 | 120/240 (j) | 265/460 (a) 120/240 (j) 120/208 (a) 460 (f) 230 (f) |
13,200 11,500 2,400 265/460 (a) 120/208 (a) 460 (f) 230 (f) |
| United States of America Portland (Oregon) |
60 | 120/240 (j) | 227/480 (a) 120/240 (j) 120/208 (a) 480 (f) 240 (f) |
19,900 12,000 7,200 2,400 277/480 (a) 120/208 (a) 480 (f) 240 (f) |
| United States of America San Francisco (California) |
60 ± 0.08 | 120/240 (j) | 277/480 (a) 120/240 (j) |
20,800 12,000 4,160 277/480 (a) 120/240 (g) |
| United States of America Toledo (Ohio) |
60 ± 0.08 | 120/240 (j) 120/208 (a) |
277/480 (c) 120/240(h) 120/208 (j) |
12,470 7,200 4,800 4,160 480 (f) 277/480 (a) 120/208 (a) |
| Uruguay | 50 ± 1 | 220 (b) (k) | 220 (b) (k) | 15,000 6,000 220 (b) |
| Vietnam | 50 ± 0.1 | 220 (k) | 380/220 (a) | 35,000 15,000 10,000 6,000 |
| Yemen | 50 | 250 (k) | 440/250 (a) | 440/250 (a) |
| Zambia | 50 ± 2.5 | 220 (k) | 380/220 (a) | 380 (a) |
| Zimbabwe | 50 | 225 (k) | 390/225 (a) | 11,000 390/225 (a) |
Circuit diagrams
![[a] Three-phase star; Four-wire: Earthed neutral](/enw/images/3/3a/DB422070a.svg)
[a] Three-phase star; Four-wire: Earthed neutral
![[b] Three-phase star: Three-wire](/enw/images/3/37/DB422070b.svg)
[b] Three-phase star: Three-wire
![[c] Three-phase star; Three-wire:Earthed neutral](/enw/images/6/63/DB422070c.svg)
[c] Three-phase star; Three-wire:Earthed neutral
![[d] Three-phase star; Four-wire:Non-earthed neutral](/enw/images/4/4e/DB422070d.svg)
[d] Three-phase star; Four-wire:Non-earthed neutral
![[e] Two-phase star;Three-wire: Earthed neutral](/enw/images/6/64/DB422070e.svg)
[e] Two-phase star;Three-wire: Earthed neutral
![[f] Three-phase delta: Three-wire](/enw/images/0/02/DB422070f.svg)
[f] Three-phase delta: Three-wire
![[g] Three-phase delta; Four-wire: Earthed mid point of one phase](/enw/images/a/a5/DB422070g.svg)
[g] Three-phase delta; Four-wire: Earthed mid point of one phase
![[h] Three-phase open delta; Four-wire: Earthed mid point of one phase](/enw/images/1/19/DB422070h.svg)
[h] Three-phase open delta; Four-wire: Earthed mid point of one phase
![[a] Three-phase star; Four-wire: Earthed neutral](/enwiki/File:DB422070a.svg)
![[b] Three-phase star: Three-wire](/enwiki/File:DB422070b.svg)
![[c] Three-phase star; Three-wire:Earthed neutral](/enwiki/File:DB422070c.svg)
![[d] Three-phase star; Four-wire:Non-earthed neutral](/enwiki/File:DB422070d.svg)
![[e] Two-phase star;Three-wire: Earthed neutral](/enwiki/File:DB422070e.svg)
![[f] Three-phase delta: Three-wire](/enwiki/File:DB422070f.svg)
![[g] Three-phase delta; Four-wire: Earthed mid point of one phase](/enwiki/File:DB422070g.svg)
![[h] Three-phase open delta; Four-wire: Earthed mid point of one phase](/enwiki/File:DB422070h.svg)
![[i] Three-phase open delta: Earthed junction of phases](/enw/images/3/34/DB422070i.svg)
[i] Three-phase open delta: Earthed junction of phases
![[j] Single-phase; Three-wire: Earthed mid point](/enw/images/8/84/DB422070j.svg)
[j] Single-phase; Three-wire: Earthed mid point
![[k] Single-phase; Two-wire: Earthed end of phase](/enw/images/c/c2/DB422070k.svg)
[k] Single-phase; Two-wire: Earthed end of phase
![[l] Single-phase; Two-wire Unearthed](/enw/images/0/07/DB422070l.svg)
[l] Single-phase; Two-wire Unearthed
![[m] Single-wire: Earthed return (swer)](/enw/images/1/16/DB422070m.svg)
[m] Single-wire: Earthed return (swer)
![[n] DC: Three-wire: Unearthed](/enw/images/9/9a/DB422070n.svg)
[n] DC: Three-wire: Unearthed
![[i] Three-phase open delta: Earthed junction of phases](/enwiki/File:DB422070i.svg)
![[j] Single-phase; Three-wire: Earthed mid point](/enwiki/File:DB422070j.svg)
![[k] Single-phase; Two-wire: Earthed end of phase](/enwiki/File:DB422070k.svg)
![[l] Single-phase; Two-wire Unearthed](/enwiki/File:DB422070l.svg)
![[m] Single-wire: Earthed return (swer)](/enwiki/File:DB422070m.svg)
![[n] DC: Three-wire: Unearthed](/enwiki/File:DB422070n.svg)
Residential and commercial consumers
The function of a LV “mains” distributor is to provide service connections (underground cable or overhead line) to a number of consumers along its route.
The current-rating requirements of distributors are estimated from the number of consumers to be connected and an average demand per consumer.
The two principal limiting parameters of a distributor are:
- The maximum current which it is capable of carrying indefinitely, and
- The maximum length of cable which, when carrying its maximum current, will not exceed the statutory voltage-drop limit
These constraints mean that the magnitude of loads which utilities are willing to connect to their LV distribution mains, is necessarily restricted.
For the range of LV systems mentioned in the second paragraph of this sub-clause (1.1) viz: 120 V single phase to 240/415 V 3-phase, typical maximum permitted loads connected to a LV distributor might[1] be (see Fig. C2):
| System | Assumed max. permitted current per consumer service | kVA |
|---|---|---|
| 120 V 1-phase 2-wire | 60 A | 7.2 |
| 120/240 V 1-phase 3-wire | 60 A | 14.4 |
| 120/208 V 3-phase 4-wire | 60 A | 22 |
| 220/380 V 3-phase 4-wire | 120 A | 80 |
| 230/400 V 3-phase 4-wire | 120 A | 83 |
| 240/415 V 3-phase 4-wire | 120 A | 86 |
Practices vary considerably from one power supply organization to another, and no “standardized” values can be given.
Factors to be considered include:
- The size of an existing distribution network to which the new load is to be connected
- The total load already connected to the distribution network
- The location along the distribution network of the proposed new load, i.e. close to the substation, or near the remote end of the distribution network, etc
In short, each case must be examined individually.
The load levels listed above are adequate for all normal residential consumers, and will be sufficient for the installations of many administrative, commercial and similar buildings.
Medium-size and small industrial consumers (with dedicated LV lines direct from a utility supply MV/LV substation)
Medium and small industrial consumers can also be satisfactorily supplied at low-voltage.
For loads which exceed the maximum permitted limit for a service from a distributor, a dedicated cable can usually be provided from the LV distribution fuse- (or switch-) board, in the power utility substation.
Generaly, the upper load limit which can be supplied by this means is restricted only by the available spare transformer capacity in the substation.
In practice, however:
- Large loads (e.g. > 300 kVA) require correspondingly large cables, so that, unless the load centre is close to the substation, this method can be economically unfavourable
- Many utilities prefer to supply loads exceeding 200 kVA (this figure varies with different suppliers) at medium voltage
For these reasons, dedicated supply lines at LV are generally applied (at 220/380 V to 240/415 V) to a load range of 80 kVA to 250 kVA.
Consumers normally supplied at low voltage include:
- Residential dwellings
- Shops and commercial buildings
- Small factories, workshops and filling stations
- Restaurants
- Farms, etc
Notes
- ^ The Figure C2 values shown are indicative only, being (arbitrarily) based on 60 A maximum service currents for the first three systems, since smaller voltage drops are allowed at these lower voltages, for a given percentage statutory limit. The second group of systems is (again, arbitrarily) based on a maximum permitted service current of 120 A.
