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Extension Cords (haha)

  1. Aug 11, 2016 #1
    So, complete hypothetical on laws governing power transmission over a distance:

    Lets say I have a generator as a source of power - and attached to that is FIVE KILOMETERS worth of extension cords. :)

    In this situation, what laws of electricity do I need to look out for?

    Voltage drop over distance?
    Amp drop over distance?
    Gauge of wire?
    Risk of fire?

    There also might be something I need to know about the extension cord itself - the plug and the power cable components, whether a three prong grounded plug would be more advantageous as opposed to an ungrounded, two prong plug, etc.

    Please help me out :)


    thank you!
     
  2. jcsd
  3. Aug 11, 2016 #2

    phinds

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    Do you understand Ohm's Law?

    Power distribution is normally done by stepping the voltage way up at the source and then down again at the distribution center, so with JUST an extension cord you're going to have a problem with voltage drop over that distance unless you have an unrealistically thick "extension cord" or you are transmitting a trivial amount of current.

    What is the purpose of your question? What is it that you really want to know how to do?
     
  4. Aug 11, 2016 #3

    anorlunda

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  5. Aug 11, 2016 #4
    Thank you for the reply.

    My goal is to transmit 100 amps five kilometres.

    I will do additional research on Ohm's law.
     
  6. Aug 11, 2016 #5

    phinds

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    You will definitely need step up and step down transformers.

    Even more to the point, you DEFINITELY need to consult a professional electrical power engineer.
     
  7. Aug 11, 2016 #6
    Are those quite heavy? Mainly on the end of the line, at the load, I have weight limitations.

    What type of voltages would be considered advantageous and why?
     
  8. Aug 11, 2016 #7

    anorlunda

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    I thought you were kidding when you said extension cord, 5 km. :warning::thumbdown::skullXbones:

    Technical differences aside, you would violate numerous safety code laws. Your insurance would be invalidated. You could kill people.

    Here on PF, we should never publicly discuss any wiring that violates the National Electric Code.
     
  9. Aug 11, 2016 #8
    It's not residential. It's underground. Unpopulated private land
     
  10. Aug 11, 2016 #9

    anorlunda

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    So you were deceiving when you said "complete hypothetical"
     
  11. Aug 11, 2016 #10
    I'm expanding the hypothetical to get around the totally imaginary legal issues here.

    Obviously wouldn't want a fire because that would be bad engineering
     
  12. Aug 11, 2016 #11

    jim mcnamara

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    If you are actually going to connect from house service drop (mains in Britain) which is 100 amps default and hookup something 5km, it will not work.
    On the practical side:
    Get a generator that meets your needs, locate the generator at the destination site. Pay an electrician to wire everything up. Much, much safer, and hugely cheaper.
    Your way or the impractical side:
    Have you priced 5km of 1 gauge copper wire? See: http://diyaudioprojects.com/Technical/American-Wire-Gauge/
    ( you will see that AWG 1 gauge is cheapest suggested for your amp requirement. BTW: I see it for US$ 1.89 per foot. It weighs a little less than 1 US pound per foot. So we have ~16000lbs X 2 conducting wires on reels. You can probably ground it locally. Dunno. )

    For AWG 1 voltage drop is .1236 ohms per 1000ft. 5km ~= 16404.2 feet X (number of conducting wires). Use Ohms law to see the destination voltage. You really would need 4/0 gauge which is much heavier and far more costly. This is an absolute no-go in terms of cost.

    Do not try what you mentioned. For what you suggest: Get professional help from your power company. There may be a transmission line much closer to the destination. Have them create the line extension and service drop. Probably way less than the $100K cost in wire. There is also CAIC assistance in most states and in Europe.

    My choice is a generator on site. Example Lowes has home standby's for under US$ 5000.
     
  13. Aug 11, 2016 #12

    berkeman

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    Well said. Thread is closed as a dangerous activity discussion.
     
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