Number of electrically separated power-carrying conductors in a power line
This tag can be used to note the number of electrically separated power-carrying conductors (cables in OSM terminology) in a power line (power=line) or a power cable (power=cable). Power transmission and distribution grids typically use three-phase alternating current (AC), so each electrical circuit consists of three conductors. Note however:
- Some circuits use only one or two conductors, including:
- high voltage direct current (HVDC) transmission links,
- single-phase or split-phase AC circuits for:
- single wire earth return (SWER) medium voltage lines sometimes used in rural areas,
- supply to electric railroads (e.g., German traction power network),
- street lighting,
- small end customers (such as individual households).
- terminal branches of the 3-phase distribution grid that carry only 2 of the phases for an immediate connection to a small set of end customers.
- Multiple independent circuits can share the same towers/poles. You may use multiple semicolon-separated values grouped by voltage (for example cables=6;3 for a line having two circuits of the first voltage and one circuit of the second voltage). See also circuits=*.
- Each conductor can be split into multiple sub-conductors (wires in OSM terminology) that are close to each other and electrically connected (this is done to reduce corona losses at high voltages and to increase the AC current carrying capacity of the conductor, as AC current tends to run best near the surface of each wire). See wires=*.
- Do not include cables that do not carry power, such as:
- protective ground cables (also called earth wires),
- passive loop cables (to reduce the magnetic field)
- telephone or other communications cables,
- guy wires (for mechanical support).
- circuits=* Number of electrical circuits of power line or cable connection.
A note on terminology
The names of the keys wires=* and cables=* may have been chosen a little bit unfortunate. The more common term for "cable" is conductor which may be a single conductor (IEV ref 466-10-19) corresponding to wires=single or a conductor bundle (IEV ref 466-10-20) corresponding to wires=double,triple,...