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On 3 Sep 2009 04:41:30 -0400, Warp <war### [at] tag povrayorg> wrote:
> It feels like everybody is writing like power cables were bare metal wires
>with nothing covering them. Why?
Because they are uninsulated.
http://en.wikipedia.org/wiki/Electric_power_transmission
--
Regards
Stephen
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Stephen <mcavoysAT@aoldotcom> wrote:
> Because they are uninsulated.
> http://en.wikipedia.org/wiki/Electric_power_transmission
I don't get it. Is that rubber around the cables a non-insulator?
I don't see bare copper here:
http://en.wikipedia.org/wiki/File:Electric_transmission_lines.jpg
--
- Warp
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> It feels like everybody is writing like power cables were bare metal
> wires
> with nothing covering them.
That's how they are actually:
"While overhead lines are usually bare conductors, rarely overhead insulated
cables are used, usually for short distances (less than a kilometer)."
from
http://en.wikipedia.org/wiki/Overhead_power_line
Insulating them for longer runs just needlessly reduces the amount of
current they can take without overheating.
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>> Rain water isn't chemically pure. (Depending on pollution levels.) Once
>> the pylon gets wet, it's entire surface is covered in a continuous sheet
>> of water, which also covers all of the cables. So why don't they short out?
>
> There are insulators between the cables and pylons so there is no path for the
> electricity to flow there.
Indeed. This is why it works when they're dry.
However, when those insulators are covered with a continuous layer of
water...
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On 3 Sep 2009 04:56:16 -0400, Warp <war### [at] tagpovrayorg> wrote:
>Stephen <mcavoysAT@aoldotcom> wrote:
>> Because they are uninsulated.
>
>> http://en.wikipedia.org/wiki/Electric_power_transmission
>
> I don't get it. Is that rubber around the cables a non-insulator?
>I don't see bare copper here:
>http://en.wikipedia.org/wiki/File:Electric_transmission_lines.jpg
You won't see copper as aluminium is used. KISS I assume that rubber or a man
made insulator would deteriate over time in such exposed conditions. Also as
Scott said the cables are under a lot of tension that would add to the cost of
connecting them without dammaging the insulation.
I have worked on underwater equipment (not power transmission) and I can tell
you that it is not easy to keep water out of things. So it is much simplier and
cheaper for overhead cables to be left bare and make sure that there is a lot of
space between them.
--
Regards
Stephen
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On Thu, 03 Sep 2009 10:06:46 +0100, Invisible <voi### [at] devnull> wrote:
>>> Rain water isn't chemically pure. (Depending on pollution levels.) Once
>>> the pylon gets wet, it's entire surface is covered in a continuous sheet
>>> of water, which also covers all of the cables. So why don't they short out?
>>
>> There are insulators between the cables and pylons so there is no path for the
>> electricity to flow there.
>
>Indeed. This is why it works when they're dry.
>
>However, when those insulators are covered with a continuous layer of
>water...
Look at the insulators, they are a strange shape. That shape ensures that they
are not covered with a continuous layer of water. Magic, isn't it :)
--
Regards
Stephen
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scott <sco### [at] scottcom> wrote:
> > It feels like everybody is writing like power cables were bare metal
> > wires
> > with nothing covering them.
> That's how they are actually:
> "While overhead lines are usually bare conductors, rarely overhead insulated
> cables are used, usually for short distances (less than a kilometer)."
Ok, maybe it's just different here (and basically everywhere else I have
been), or they are really good at making it *look* like the cables are
covered in black rubber. I certainly was fooled.
Do they paint them like that?
--
- Warp
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scott wrote:
>> I was thinking more of when everything has been covered in a
>> continuous layer of water...
>
> Are you sure that every part between the pylon structure and the cable
> can get wet to form a continuous path? It seems to me like part of the
> design of the insulator is to keep other parts dry:
>
> http://en.wikivisual.com/images/3/33/Pylon.detail.arp.750pix.jpg
How do you figure that?
> Even if it does *all* get wet, it's going to be a really thin layer of
> water, and even non-pure water is not a particularly good conductor, if
> you do the math the resistance probably comes out pretty huge.
You're aware that those cables are carrying several *million* volts?
Still, perhaps all that current would just vapourise the water - and
then it wouldn't be there any more...
> BTW, that photo also shows the dampers attached on the cables either
> side of the fixing point.
Well, this stuff clearly works - it's just a mystery to me *why* it
works. ;-)
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> Ok, maybe it's just different here (and basically everywhere else I have
> been), or they are really good at making it *look* like the cables are
> covered in black rubber. I certainly was fooled.
>
> Do they paint them like that?
It's just the dull grey of aluminium oxide you are seeing on the outer
surface. If you looked close and polished them a bit you'd see nice shiny
aluminium :-)
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>> I mean, seriously. Any moron can write a bunch of gibberish that doesn't
>> make sense. But where's the entertainment in that?!
>
> I don't think everybody can write scripts of that quality. It requires
> expertise and talent.
It takes expertise and talent to write scripts which *make sense* and
are *interesting*. The X-Files lacks both of these qualities in spades.
[OK, you can argue about whether or not something is "interesting". But
whether something makes sense or not is pretty objective. It's hard to
find something interesting when it's unintelligable gibberish.]
> And some people like fiction for entertainment. If you don't like it,
> that doesn't mean nobody else souldn't like it either.
Sure, fair enough. I'm just puzzled as to why such a low-quality show
was so absurdly popular.
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