personally i hate pylons ...they look awful, i have no problem with posts , but there is no way you could carry that much power on a post.
well the e-petition talks about 'wooden pylons' - which to me means telegraph poles so I think you're OK with this one

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National grid have agreed now to put nearly a quarter of the mid Wales cables underground
http://www.bbc.co.uk/news/uk-wales-mid-wales-24141013
so it can be done, despite, the technical issues if enough people put pressure on to save the visual environment.
well, yes, it can be done over short distances (in the article you quote, 13km of the 53km route) - but at a cost, both in terms of installation cost and energy lost in transmission. The practical limit for underground AC transmission is 60km before the power losses make it uneconomic, so if they put the whole 53km underground a large proportion of the energy generated by the windfarm would be lost in transmission - or in the expensive and lossy phase-correction stations needed to get the energy to the other end of the line - making a farce of the whole project renewable energy windfarm project.
Of course if they do end up burying the whole 53km that would play into the hands of the NIMBYs who would then hold it up as an example of how wind farms don't produce useful amounts of energy

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In the future, HVDC may become cheap enough for the cables to be buried, but for now I'd rather have the poles, and the renewable power rather than another array of nuclear power stations and a pole-free view - I care more for the global environment than the visual environment - but maybe that's just me

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