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DC ring main around the earth

Discussion in 'Electrical Engineering' started by bruce varley, May 20, 2004.

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  1. bruce varley

    bruce varley Guest

    I heard this suggestion a long time ago, not sure where. It's pretty extreme
    and there are lots of factors against it, but this is one forum which should
    at least consider it.

    The idea is to run a BIG DC ring main around the earth, traversing many
    equatorial parts where the solar energy (and in some places wind) is
    moderately reliable. That way you can have relatively constant energisation
    through renewable sources. Spurs running north and south would feed the
    energy to consumers.
  2. Ohhh! Ohhh! Can we get the engineering for that? Let's see, 10% of 5
    trillion would be a very nice addition to the company bottom line - even
    if it was spread out over 25 years or 50 years.

    Aside from the ruinous high cost of consulting engineers to design the
    thing, practical problems with this would include:

    1. High voltage DC circuit breakers are still pretty much a research
    topic, and not something you can order from a catalog. This means that
    right now it's impossible to tap a HVDC line - multipoint distribution
    is not practical without some way to protect the branches.

    2. There's probably an upper physical limit on the DC voltage you could
    use, in terms of how much corona loss you can stand per km for conductor
    bundles of a practical size. I suspect the limit is well under 2
    million volts pole-to-pole. This severely limits the transmission
    distance - I doubt a line even 10,000 km is practical.

    Right now this part of the world is looking at a much less ambitious
    connection to take advantage of the fact that when it's supper hour in
    Ontario, the kids are just getting out of school in Alberta - thereby
    spreading out the peak loads, and also allowing Manitoba to sell hydro
    power in both directions. Not 5 trillion, but I'm sure 5 billion
    dollars would get used pretty quickly.

  3. John Gilmer

    John Gilmer Guest

    Come on: the "taps" would be just like the terminals. They would be you
    "basic" (and expensive) DC-AC bi-directional conversion stations.
    Over land it would be just like the situation today with AC networks: Power
    is "wheeled" from end to end rather than sent along a un-tapped transmission
    line. For the necesssary underwater links, the present technology just
    isn't up to the problem.
    Amen. The intra-continental links are not yet fully developed (or
  4. Don Kelly

    Don Kelly Guest

    This can be done-in theory- it is expensive and each such tap requires both
    a rectifier and inverter as well as AC reactive sources. That is each would
    be a "back to back station" If you wanted feeder spurs to be DC then the
    equivalent of 3 AC circuit breakers would require the equivalent of 3
    converter stations. as well as the availability of a strong AC system at
    each tap point. At some point "feasibility" degenerates into a no go
    situation. This point is reached long before consideration of a "round the
    world link".>In the case of a cross-continent tie -the tap points would be
    reduced to back to back converters such as those in Japan,
    Alberta/Saskatchewan and Eel River New Brunswick (all of which are DC for
    stability or frequency conversion needs ). At these "taps" the local
    systems do need some muscle.
    Again, in present AC systems, circuit breakers at reasonable cost and
    effectiveness are very important. How far apart must the 'taps" be to make
    it either economically or technically worth while to use such a tapped DC
    system? (yes- there is in fact such a system if I remember correctly- the NW
    power pool DC link which ties strong areas of generation to major loads and
    is in parallel with AC ties

    It all boils down to the merits and demerits of any proposed situation: Load
    here---Generation here---what's the best way to get them married? In some
    cases, don't bother- intercontinental transfer may have no net benefits and
    a lot of costs even if technology was up to the task.

    Don Kelly

    remove the urine to answer
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