power systems

Discussion in 'Homework Help' started by vvkannan, Nov 2, 2008.

  1. vvkannan

    Thread Starter Active Member

    Aug 9, 2008
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    A basic question,but i have not got the answer for it.In power systems
    whenever a fault increases current increases immediately.But how does it increase?
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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    I'm not sure I really understand your question, but if you are talking about protection systems

    Protection systems work by providing a low resistance path for the current, in the event of a fault.
    This path contains a disconnection device, which may be a fuse or breaker that passes normal levels of current but disconnects automatically if the current increases.
    The current increases because of the low resistance path.
     
  3. vvkannan

    Thread Starter Active Member

    Aug 9, 2008
    138
    11
    Thank you for replying
    I am sorry .I have not been clear and that's because i really cant understand the basics
    Let me try to be specific and here's my first doubt.
    Let's consider a 3 phase system.
    Now capacitances are formed between the lines and the ground.
    Are the capacitances formed with one plate as the line and the other as the ground?
    If so then how would the capacitive currents flow between them ,that is, how would capacitive currents flow between the plates(line and ground) and without any external circuit.
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
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    For any circuit, you need to distinguish between normal operation and fault conditions.

    Nothing in this world is 100% efficient in normal operation.

    AC electrical power distribution suffers power loss due to capacitance as you describe. This is negligable for domestic situations and only important in high voltage (national) grids.
    Generally more power is lost due to the resistive heating of real world conductors, which are not perfect.


    Three phase is not 'basic' so perhaps you need to consolidate your basic theory first.

    Any AC or DC distribution system does not require a ground in normal operation.

    The ground is part of the safety arrangement and should only come into play in fault conditions.
     
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