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Powerline Slackers
Cars, growing trees, falling trees, icestorms and other things can break a mains cable carried on hydro poles. So, | |
The power cable has a small loop on it at every pole, attached with a frangible bracket which strength is less than that of the cable.
If a cable gets pulled too much the bracket breaks; more than one pole's bracket may be broken, depending on how far the line is pulled.
This allows power to remain
uninterrupted during extreme natural and manmade circumstances, while people can remain unelectrocuted, and trees unshaven (simply unloop a couple of poles and move the wire out of the way of the branch, temporarily).
The downside is, of course, the cost of the 7% extra cable required and concommitant power loss, which would increase from 2% to 2.14%.
Self Promotion
Power_20Line_20Shaker
Same general idea. [MechE, Jul 24 2015]
If you sell enough of these the problem is prevented
Gondola_20with_20the_20Wind
[normzone, Jul 24 2015]
[link]
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How are you expecting the line crews to be able to reinstate a failed pole without taking the power off? Are they and their equipment made from pure ceramic? How are the cables slung in such a way that the pole can fall without falling onto at least half of the cables? |
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If you want to avoid power outages from downed poles, put your power lines underground. The limitation here is capacitance losses - but having lived my entire life in cyclone affected areas - it's not the high tension lines that go down in weather events, but rather the street side poles. |
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// Cars, growing trees, falling trees, icestorms and other things can break a mains cable carried on hydro poles. // |
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Buried cables are much less vulnerable, although more expensive to install and maintain. |
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Thing with buried cables is there's a rather large of bother and (I imagine) concrete, involved. |
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//more expensive to install and maintain// |
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much, much more expensive to install and maintain. |
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Some alternative solutions: |
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-The powerline is released from the pole when unusual force is applied. This could be an active or passive component. The powerline would still be supported by adjacent powerlines. |
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-The powerline is supported at each pole by rollers/sliders so the tension is distributed to further power poles. |
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-Each powerline is a pair of touching wires that can slide against each other and thus lengthen the powerline when sufficient force is applied. |
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-The poles are flexible or gimbled and counterweighted so that lateral force would only bend/angle the pole rather than fail catastrophically. |
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If one pole fails, how do the adjacent poles know? If
they don't know, what's to stop several poles failing,
leaving an intact, live cable drooping down to the
ground? |
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The adjacent poles don't really "know" anything. Taking, for example, a tree-branch falling on the line: if it's too heavy the bracket on one of the poles will break, dropping the line down a couple of feet. If the deceleration isn't enough and it's still too heavy, then another bracket on the next pole over will break, dropping it down another couple of feet. |
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Et cetera, maybe until the powerline hits the ground. The head office gets the report of which poles' brackets have broken off, through the line. |
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Either way, there's a "live" wire on the ground, but if there's still insulation on it then it's safe, certainly moreso than a broken end. |
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At which point it occurs to me that some might think I'm talking about the very high tension wires: no, I mean the neighbourhood ones, though the same principle could be applied. |
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Hmm. Generally, aluminium is used for power lines
because significant spans of copper are so ductile
they'd drop off the tower like syrup. How about copper
inside a tough aluminium shell. That way a tree would
break the outer shell, but the copper would stretch
and thin. Allowing continuity to be maintained at the
cost of lower capacity. |
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Or, you know, bury them like a civilized people, it
makes photographers happy. |
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//Either way, there's a "live" wire on the ground, but
if there's still insulation on it then it's safe, certainly
moreso than a broken end. // |
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In general, powerlines on overhead pylons aren't
insulated. |
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Pretty sure ours are, though they get ragged over the years: I'll check when the sun's out. |
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[Custardguts] is spot on. And all the others who said the same
thing basically. |
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I hear Greeks are going cheap these days. But I wouldn't trust them to support critical infrastructure for very long... |
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^But are they tall enough? |
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Overhead high tension wires don't get insulation. It adds
weight; it makes them physically larger, which then catches
more wind resistance and more snow/ice loading. |
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^ Well good, then if also used on the high-tension (ie: really high voltage) lines, then a bracket breaking can get the line shut down before it hits the ground. |
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If it's safe to have the power line lying on the ground, why not leave it there all the time? |
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//^But are they tall enough?// |
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You can always stack a pile of them, if need be. |
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[FT] The results I've seen firsthand after a hurricane were
that miles of poles were broken off and cables(bare) were
intact for the most part. More poles would make a stronger
structure. This and one of the neighbors has a company that
builds power lines and that is his recommendation also. Put
the poles closer together. |
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You'd need a smaller planet to put the poles closer together. If anything, this place is getting too crowded as it is. |
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//[MechE]s idea is virtually the same// The result is the same for some circumstances; the method differs. |
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This one started out as a way to keep both trees and power-distribution happy. If a branch starts interfering with the line, or vice versa, just unhook the line from the pole and re-set it under the branch. |
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Underground electrical lines seem just too tempting to run
through people's yards, and people digging in their
backyards without a permit have been known to sever them
inadvertently. |
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Only local lines should run shallow enough to be
inadvertently excavable. I know this because the
local line serving the nearby village was shallow
enough under my land to be inadvertently excavated. |
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//digging in their backyards without a permit// Absolutely shocking! What kind of a libertarian nightmare is the world turning into these days! |
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//[MechE]s idea is virtually the same// I thought that at
first, but it's not, quite. My idea was to shake loose
whatever lands on it, this idea is about surviving whatever
lands on it. |
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Last year we had almost a solid week of freezing rain/drizzle/fog. |
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Since we hadn't had any supercooled precipitation worth mentioning in a couple of decades, the fallen branches included the ones that would have broken off years ago. Lost power to most of the city for a few days (in some areas a couple weeks) while power crews from all over set things right. |
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