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Power grids

  1. Jan 6, 2015 #1
    I have got to know that the voltage and frequency of the supply in the power grids is kept as infinity.>!! But what is the reason behind it..??
    Well for the voltage to be infinity , I have studied that losses are inversely proportional to square of supply voltage ..so higher is the voltage , lesser will be the losses..!!
    But what is the reason behind infinite frequency..please explain.>!!
  2. jcsd
  3. Jan 6, 2015 #2

    Doug Huffman

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    Gold Member

    Neither voltage nor frequency are ever infinite or maintained at infinity. AC Transmission frequency is the same as distribution frequency. Voltage may be much higher, but infinity is a fiction.
  4. Jan 6, 2015 #3
    I think that you might have heard the phrase, an infinite grid, and don't understand what it means.
  5. Jan 6, 2015 #4


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    As has been pointed out, you seem to have some confusion on how AC power is distributed. Can you post links to the reading that you have been doing that is causing these questions?
  6. Jan 6, 2015 #5
    In my opinion what you heard –may be-it is that short-circuit power of a grid could be considered infinity if you calculate short-circuit current down stream a transformer. It will be a little bit conservative but for a rough appreciation it is ok. As already it is written in above posts the system frequency and the voltage would stay as rated.
  7. Jan 6, 2015 #6
    Bu this is what told to us by our prof. !!
  8. Jan 6, 2015 #7


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    Then he be wrong. I was once told by someone who should have known better that the reason the load was placed in the collector on grounded emitter BJT switch circuits (relay coil, LED, etc.) was because the collector typically has more heat sink area. Just because they should know does not mean they do know.
  9. Jan 6, 2015 #8


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    Staff: Mentor

    Or he be right and the OP misheard...
  10. Jan 6, 2015 #9
    OP misunderstood -I think. We be callin' the grid the infinite machine or the infinite grid (even though it is not).
  11. Jan 7, 2015 #10


    Staff: Mentor

    I think the OP misheard slightly. In power analysis, it is common to use the concept of an infinite bus.

    An infinite bus is one that will maintain constant magnitude, phase, and frequency of voltage, while supplying any current or any power. It is a simplifying concept, not something that we find in real life.

    In "load flow" analysis where we calculate the voltages, current, and power flows for an entire power grid, it is necessary for one node in the network to be treated as an infinite bus.
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