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Public-images-osm logo.svg voltage
Symbole voltmetre.png
For describing the voltage of power lines, cables, and substations. Edit or translate this description.
Group: Power
Used on these elements
may be used on nodesmay be used on waysmay be used on areasshould not be used on relations
Useful combination
Status: in use

The nominal voltage of a power line, cable, substation, or rail. Voltages can sometimes be safely determined from signage on the support structures (or signs on sites where underground cables run). Alternatively, they can be deduced from the length of insulators, conductor spacing, or other characteristics, in combination with some general knowledge of the power system.

Values should be entered in volts without the unit or thousand delimiter. For example, for a 15 kV line, the value should be voltage=15000, not “15 kV”, nor “15,000” or combinations of this.

When multiple voltages are in use, for example on a power line carrying two circuits, or a substation converting between two voltages, the voltages should be separated by semicolons with the highest voltage listed first: voltage=275000;132000.

This tag should not be used for transformers - the voltage:primary=* and voltage:secondary=* tags should be used instead.

OpenInfraMap shows power lines colour coded by voltage range and its exact value, allowing for quick analysis of the OSM data.

Nominal, rated, and maximum voltages

There is some disagreement between system operators about "nominal" line voltages. A line which is classified 400 kV in the UK and a one which is classified as 420 kV in continental Europe may be carrying very similar levels of voltage in practice - it is only the nominal voltage designation which is different.

In some areas the "nominal" voltage published may actually be the maximum continuous rated voltage, especially as methods for regulating voltage improve so lines can be run closer to their theoretical maximum.

There's no easy way of finding out the actual levels of voltage, so the system operator's designation should be used, but it should be noted that these "nominal" voltages aren't directly comparable between countries.

IEC 60038 defines a number of voltage ranges, which may be useful for voltage classification.

List of min/max AC voltages as defined by IEC 60038, and typical values used by each operator/country (kV)
Nominal Max Nominal Max Belgium Canada Great
Ireland Indonesia Norway Philippines Taiwan United States
Alberta BC Hydro Manitoba Hydro Hydro-Québec
Series 1 Series 2
3 3.6
4.16 4.40 4.16 4.16
6 7.2 6
6.6 6.9
10 12 10
11 10 11
12.47 13.20 12.47 12.47 12.47
13.20 13.97 13.2
13.80 14.52 13.8 13.8
15 17.5 15
20 24 20
20 20 22 23
24.94 26.47 24.94 24.94 24.94 24.94
30 36 36 33 33
34.50 36.50 34.5 34.5
35 40.5 38
45 52 45
66 72 70 69 (AltaLink, ENMAX)
72 (ATCO Electric, EPCOR)
69 69 66 70 66 69 69 69
110 123 115 115
110 110 115 115
132 145 138 (AltaLink, ENMAX)
144 (ATCO Electric)
138 138 132 132 138 138
150 170 150 161 150 161 161
220 245 220 230 (Montana-Alberta Transmission Line only)
230 230 230 220 230 230
275 300 300 287 315 275 275 275 300 287
330 362 360 345 345
380 420 380 400 400 420
500 550 500 500 500 500 500 500
735 765 735
765 800 765

HVDC systems

Some HVDC systems use the earth or a grounded conductor as return. Not only monopolar HVDC schemes use such a device, it can be also found at many bipolar HVDC schemes in order to allow an operation of the scheme in monopolar mode, however in most cases with reduced power. The grounded conductor must be always installed with insulators on the support structures as uncontrolled ground currents lead to undesired electrochemical corrosion. The grounding must be performed therefore with specially designed grounding electrodes, situated and designed so, that no electrochemical corrosion occurs.

The grounded conductor, which is called electrode line, when it runs from a converter plant to a grounding electrode, can but must not be mounted on the towers carrying the high-voltage poles of the HVDC scheme. It can also run on a separate line or fixed on towers of AC lines. As it runs into a ground electrode, it can serve as ground wire, whereby the insulators must be equipped with lighting arrestors.

If the towers of an HVDC line carry also a conductor used as grounded return, the voltage must be described with "HVDC voltage ; 0", if not than set just the HVDC voltage. For AC-lines carrying a grounded return conductor of an HVDC-scheme, set as voltage "AC voltage(s) ; 0" and as frequency "AC frequencies ; 0".

Ground return conductors of HVDC-schemes must be always considered at cable count.

The voltage value 0 for such lines is strictly spoken not correct. In fact, it shows a voltage against ground which is equal to the product of the line current and the sum of ground resistance and resistance of line to grounding point, but as the current value depends on the load and resistance values are often not available, the value 0 is a good choice as it implies, it is grounded.


A high-voltage transmission line carrying two circuits with a voltage of 110 kV would use the following keys and values:

A transmission line carrying two circuits at 110 kV and one at 66 kV:

An electrified railway track in Germany with overhead power supply:

Nearly the same for a subway with separate rail for power supply:

A street with overhead wires for trolley buses:

A distribution substation, stepping down the voltage from 11kV to 400V for use by houses:

See also