|Number of electrical circuits in a power line, cable or connection|
|Used on these elements|
|Status: in use|
|Tools for this tag|
Use circuits=* to note the number of electrical circuits (601-02-28) of any power line, cable or connection. The tag was primarily intended for underground cable connections where the number of physical cables is unknown or has no simple relationship with the number of circuits and is now used on any line.
In power transmission a circuit (as defined in Electropedia 601-02-28) consists of required conductors to allow current to flow from a power source to the load and back to the source. Think of a battery and a load such as a light bulb connected by two wires. Current will physically flow from the battery to the load via the negative wire and return to the battery via the positive wire. For three-phase AC power transmission things are slightly more complex as three different AC currents flow in the three conductors forming a circuit. The currents flowing in the three phase conductors will tend to cancel out one another and unless there is an additional neutral conductor the net current will be zero.
One-phase AC transmission systems are also known. One example is traction power systems for railways using two-conductor one-phase transmissions. Sometimes one-phase systems require just one metallic conductor by using earth as the return conductor. Examples are Single Wire Earth Return systems used in some rural areas and monopole HVDC connections using earth or seawater as the return path.
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When to use
Note that this tag should not replace the cables=* tag.
The circuits=* tag should be used in the following situations.
- Underground or underwater cable sections (power=cable). Even if cables=* is still relevant to describe physical layer, it may be useless for calculating the number of circuits here since the number of physical cables per circuit varies (typically 1, 3 or 6 independent cables per circuit). The amount of cables can be seen at section extremities when it comes overground and be unknown to mappers once underground/underwater.
- Overhead power lines (power=line or power=minor_line) in the following situations:
- The physical line supports several circuits (whatever how many cables compose a single circuit)
- Several apparent circuits (2 * 3 cables for instance on a continental three-phases network) are operated as one effective circuit. This means that the several apparent circuits are wired in parallel and connected to a single bay in the substation.
How do you know the number of circuits?
The amount of cables can be seen at section extremities when it comes overground and be unknown to mappers once underground/underwater.
When a link between two substations is entirely underground the data may sometimes be available in public information from the grid operator. However, always verify that such information is available under a license that is compatible with the ODbL license before using it!
|Power line transition to underground cable section. The overhead line clearly appears to support 2 circuits.