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%.
-- FlyingToaster, Jul 23 2015

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]

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?

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.
-- Custardguts, Jul 23 2015


// Cars, growing trees, falling trees, icestorms and other things can break a mains cable carried on hydro poles. //

Buried cables are much less vulnerable, although more expensive to install and maintain.
-- 8th of 7, Jul 23 2015


Thing with buried cables is there's a rather large of bother and (I imagine) concrete, involved.
-- FlyingToaster, Jul 24 2015


//more expensive to install and maintain//

much, much more expensive to install and maintain.
-- AusCan531, Jul 24 2015


Some alternative solutions:

-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.

-The powerline is supported at each pole by rollers/sliders so the tension is distributed to further power poles.

-Each powerline is a pair of touching wires that can slide against each other and thus lengthen the powerline when sufficient force is applied.

-The poles are flexible or gimbled and counterweighted so that lateral force would only bend/angle the pole rather than fail catastrophically.
-- xaviergisz, Jul 24 2015


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?
-- MaxwellBuchanan, Jul 24 2015


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.

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.

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.

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.
-- FlyingToaster, Jul 24 2015


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.
-- bs0u0155, Jul 24 2015


Or, you know, bury them like a civilized people, it makes photographers happy.
-- bs0u0155, Jul 24 2015


//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. //

In general, powerlines on overhead pylons aren't insulated.
-- MaxwellBuchanan, Jul 24 2015


Pretty sure ours are, though they get ragged over the years: I'll check when the sun's out.
-- FlyingToaster, Jul 24 2015


[Custardguts] is spot on. And all the others who said the same thing basically.
-- blissmiss, Jul 24 2015


Use more poles.
-- cudgel, Jul 24 2015


I hear Greeks are going cheap these days. But I wouldn't trust them to support critical infrastructure for very long...
-- RayfordSteele, Jul 24 2015


^But are they tall enough?
-- cudgel, Jul 24 2015


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.
-- lurch, Jul 24 2015


^ 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.

//Use more poles// why ?
-- FlyingToaster, Jul 24 2015


If it's safe to have the power line lying on the ground, why not leave it there all the time?
-- pocmloc, Jul 24 2015


//^But are they tall enough?//

You can always stack a pile of them, if need be.
-- RayfordSteele, Jul 24 2015


[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.
-- cudgel, Jul 24 2015


You'd need a smaller planet to put the poles closer together. If anything, this place is getting too crowded as it is.
-- RayfordSteele, Jul 24 2015


//[MechE]s idea is virtually the same// The result is the same for some circumstances; the method differs.

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.
-- FlyingToaster, Jul 24 2015


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.
-- 21 Quest, Jul 24 2015


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.
-- MaxwellBuchanan, Jul 24 2015


//digging in their backyards without a permit// Absolutely shocking! What kind of a libertarian nightmare is the world turning into these days!
-- pocmloc, Jul 24 2015


//[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.
-- MechE, Jul 24 2015


Last year we had almost a solid week of freezing rain/drizzle/fog.

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.
-- FlyingToaster, Jul 24 2015



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