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> Does voltage even matter in this case? Isn't amperage the important bit?
The current (amperage) in the cable is pretty meaningless if we're talking
about accidents when someone or something touches the cable. Whether there
is zero or ten million amps going along the cable, when you (or some object)
touches it, it is the voltage of the cable that will determine the severity
of the outcome.
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scott wrote:
>> But trees encroach on power lines all the time. I can look out my
>> window and see half a dozen...
>
> You have one of these outside your window? o_O
>
> http://www.idonohoe.com/biking/gallery/pylon.jpg
Ah, no, although I know of some within a few miles of here.
No, I mean the stuff that runs down your street and branches to every house.
> If you mean the low voltage cables on wooden poles that are much closer
> to the ground, then maybe those ones are insulated (we don't have many
> of those here, the cables mostly go underground once they come off the
> pylons)? They don't have to go long distances so the extra cost is
> probably justified by the high risk of stuff hitting them.
OK, so the local stuff is probably insulated due to risk, while the high
voltage stuff used for long-distance transmission is left uninsulated.
That makes sense.
...Chambers
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> No, I mean the stuff that runs down your street and branches to every
> house.
Ah ok, yes that would need to be insulated! I don't think we have cables
like that anywhere here (or if we do it's really uncommon), it's all
underground apart from the high voltage long distance stuff. I remember
when I visited Japan they had crazy amounts of cable in the air, with
transformers at the top of poles etc, I'd never seen anything like it:
http://img1.photographersdirect.com/img/11943/wm/pd540134.jpg
I guess once you start putting power and telephone above-ground, things get
very messy very quickly in heavily populated areas. Underground I suspect
you have the same, it's just hidden from sight!
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On 09/07/09 02:24, scott wrote:
>> Does voltage even matter in this case? Isn't amperage the important bit?
>
> The current (amperage) in the cable is pretty meaningless if we're
> talking about accidents when someone or something touches the cable.
> Whether there is zero or ten million amps going along the cable, when
> you (or some object) touches it, it is the voltage of the cable that
> will determine the severity of the outcome.
Not really. It's also the amount of available charge. If you get a 10
kV shock, but the supply had very few Coulombs in it, you'll barely feel it.
But if you get a 100 V shock with an almost limitless supply of
Coulombs, you certainly will feel it, and in rare occasions, die because
of it.
Current *is* a factor. Certainly: Voltage will dictate an upper bound
on the current. However, if there's not enough charge to maintain that
upper bound, then voltage becomes irrelevant because it can't sustain
that current.
--
"I find you guilty!", said the judge with conviction.
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> Not really. It's also the amount of available charge. If you get a 10 kV
> shock, but the supply had very few Coulombs in it, you'll barely feel it.
I was kind of assuming that the power station grid could spare the extra 100
mA or so needed to kill you :-) But yes, if you find a 10 kV supply with
very limited current sourcing capability (like the ones used in small CCFLs
in old LCDs) it's difficult to kill yourself because of the very limited
current sourcing capability.
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scott wrote:
> http://img1.photographersdirect.com/img/11943/wm/pd540134.jpg
A lot of that is phone wires, yes.
> I guess once you start putting power and telephone above-ground, things
> get very messy very quickly in heavily populated areas.
Only when it's poorly planned. You can have nice above-ground stuff that
just has one set of power cables and one set of phone cables running down
the street and branching once for each house.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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Darren New wrote:
> Only when it's poorly planned. You can have nice above-ground stuff that
> just has one set of power cables and one set of phone cables running
> down the street and branching once for each house.
>
>
As with almost all things, a lack of planning can lead to "ugly", or
poor functionality.
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Mr. Art wrote:
> As with almost all things, a lack of planning can lead to "ugly", or
> poor functionality.
Of course, planning well can be difficult when you're trying to guess the
best technology for 50 years in the future, or when you're trying to guess
how many customers will be using your service in 30 years, or etc. It's
hard to blame the planners for this sometimes.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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Darren New wrote:
> Mr. Art wrote:
>> As with almost all things, a lack of planning can lead to "ugly", or
>> poor functionality.
>
> Of course, planning well can be difficult when you're trying to guess
> the best technology for 50 years in the future, or when you're trying to
> guess how many customers will be using your service in 30 years, or
> etc. It's hard to blame the planners for this sometimes.
>
Who said anything about blame?
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Mr. Art wrote:
> Darren New wrote:
>> Mr. Art wrote:
>>> As with almost all things, a lack of planning can lead to "ugly", or
>>> poor functionality.
>>
>> Of course, planning well can be difficult when you're trying to guess
>> the best technology for 50 years in the future, or when you're trying
>> to guess how many customers will be using your service in 30 years, or
>> etc. It's hard to blame the planners for this sometimes.
>>
> Who said anything about blame?
Me.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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