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Wind turbine domestic grid connection

Discussion in 'Electrics UK' started by SparkyTris, 14 May 2010.

  1. SparkyTris


    24 Nov 2004
    Thanks Received:
    United Kingdom
    A farmer pal of mine is installing a mid size wind turbine - an 80kW machine - in order to take advantage of the Feed-In Tariff. He runs an organic farm and a hostel in the farmyard. The whole property is supplied by a 50kVA transformer adjacent to the house - this takes the overhead 33kV 3-phase line down to farm 3-phase (3 phases of 240V to earth I think, more properly referred to as 415V). His electric bills are understandably quite large. His primary aim is to use the wind turbine to power his farm/hostel, for "free". Obviously when it is calm, he will have to use "normal" electricity. But When it is windy, he wants to use only his wind electricity for the farm and export any surplus to the grid.

    He wants to put the windmill about 500 metres away from the house. Very close to this site is an 11kV single phase overhead spur supplying a small outlying settlement.

    He has consent from the electric company (Scottish & Southern) to grid connect his turbine, and on this written permission came their plan which was to upgrade the single phase spur to 3 phase 33kV, and put a double pole transformer in, all at his expense - about £80k, according to them.

    Being cynical, it seems that this plan is attractive to S&S because they get to upgrade an old spur at someone elses expense AND they get all of his wind energy for something like 4p per unit, whilst the owner of the windmill goes on paying the normal rate - 15p per unit - for his electric on the farm.

    My pal wants to use his wind energy. I think this should be possible simply by taking the windmill's 3-phase output, and connecting it (through the appropriate switchgear) straight onto the existing 3-phase incomer in his property. He would have to install an export meter I presume, and upgrade the transformer.

    Can anyone comment on this? Sorry for the waffle, but it seems neessary to give the full picture. Please understand that we are not attempting to cowboy this in ourselves, we are just fairly practical & technically savvy people who want to understand all the principles involved.

    I think I understand that, (apart from the accreditation necessary to wire all this in):

    1. the wind turbine must be able to sense when there is no grid power and isolate itself, in order to NOT feed power onto the grid alone, possibly killing a linesman. Do grid connect inverters take careof this? or is there a separate device?

    2. the grid connect inverters must supply each phase so that it is synchronised with the grid, and they take care of this themselves. also.

    3. The wind turbine has its own load bank, and it diverts its energy there when disconnected from grid. (?) what form does this take? resistors?

    Could anyone please fill me in on:

    1. How do you make the energy from the windmill flow "uphill" back into the grid?

    2. the appropriate switchgear needed to connect the windmill output onto the farms industrial 3 phase board?

    3. will the old transformer that was installed to supply the farm work in reverse when exporting energy? if it is just a transformer - ie, primary coil, core, secondary coil, then it will step-up just the same as stepping down?

    I look forward to the discussion that I hope will ensue!!
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  3. Steve


    15 Apr 2005
    Thanks Received:
    United Kingdom
    He could simply connect the windmill so that it ONLY supplies power to the grid - ie. connect it before your meter. And get paid for all that the windmill produces (I understand they pay more per unit for feed ins than they charge for consumption - not sure how that works).

    IMO this would be the cheapest and least complex option.

    BUT if he does this, he might as well let the DNO build a windmill of their own and charge them a wayleave for the windmill. ;) Depends which is the most lucrative I guess.

    Whats his total budget :eek:
  4. Lectrician


    18 Jul 2004
    Thanks Received:
    United Kingdom
    You get better rates through a single metered connected as opposed to two.

    The supply would need to upgraded to atleast 80kva - and the DNO would have to be informed of the intended export.

    Very simply, you connect the turbine via it's control panel to your supply 'as if it was a load'. The power will flow to where ever it is needed - the farm or the grid.
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    3 Sep 2019
    United Kingdom

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