On 15/01/2013 15:31, François Lacombe wrote:
But "aerial line" refers to all the conductors transmitting different
lives/phases whereas underground power cable, at high voltage,
refers to only one phase/conductor.
http://www.nexans.no/eservice/Norway-no_NO/fileLibrary/Download_540199654/Norway/files/Underground_power_cables.pdf
*So, many underground cables are needed to set up a line!*
You may have multi-conductors cables up to 150 kV but you still have
several conductors.
Insulation is mandatory underground because we can't put enough space
between conductors, instead of what is done in the air.
The right question is "*do we map cables separately or lines*"? It's
all about the vocabulary we use.
http://2.bp.blogspot.com/-CnkQkGiPmbs/UFM6M2N0lUI/AAAAAAAAArk/IMZxA3i6SmY/s1600/tunnel.png
If we map cables we must do the same for both aerial and underground
lines and I'm not sure it would be really efficient.
Well, I think we need to properly define what is meant by "power=cable".
The wiki page isn't entirely clear on that matter. I'm usually mapping a
underground cable connection as a single way tagged as "power=cable" and
indicating the number of physical cables with "cables=*" (if it is known
to me). Your interpretation is obviously that each physical cable
should be mapped as "power=cable" (which you can't if you don't know the
number of cables).
Considering that "power=line" and "power=cable" are used so extensively
I think it is a bad idea to redefine the meaning of them as it would
break a lot of things and confuse mappers. The distinction between
'line' for overhead power lines and 'cable' for underground cable
connections is easily understandable by the average non-expert mapper.
My proposal is to clarify both the 'line' and 'cable' wikis as follows:
"power=line" should represent a connection comprising UN-insulated
conductors mounted on towers or other supporting structures, normally
over ground.
"power=cable" should represent a connection consisting of one or more
insulated cables (whether underground, underwater, in a tunnel or
overground).
The number of physical cables for a cable connection should be indicated
by "cables=*" when known. I'm currently drafting a wiki page for a
"circuits" tag to describe the number of electrical circuits, especially
useful for cable connections having an unknown number of cables, see
http://wiki.openstreetmap.org/wiki/Key:circuits.
Ole
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