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    danar's Avatar
    danar Posts: 69, Reputation: 2
    Junior Member
    		  
    #1

    Oct 20, 2007, 03:21 AM
    DC short circuit calculation.
    Any one familiar with DC short circuit calculation?
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
    Uber Member
    		  
    #2

    Oct 21, 2007, 05:21 AM
    What do you mean "familiar"?

    Sure, I am familiar.

    What is your specific question?

    Will this help?
    Calculation of short circuit currents

    The answers you receive would be better if you were not so cryptic with your questions.

    I thought "engineers" tend to be more detailed and specific. Add more detail than just one sentence broad questions.
    danar's Avatar
    danar Posts: 69, Reputation: 2
    Junior Member
    		  
    #3

    Nov 7, 2007, 04:33 AM
    What I mean is DC short circuit current calculation.. we use to do AC short circuit current calculation but for DC I think it has different parameters...
    SuryaGG's Avatar
    SuryaGG Posts: 1, Reputation: 1
    New Member
    		  
    #4

    Jul 28, 2008, 12:35 AM
    tkrussell,

    I am also looking for the answer to danar. The link in your reply does not discuss anything about DC (power system) short circuit current calculation.
    danar's Avatar
    danar Posts: 69, Reputation: 2
    Junior Member
    		  
    #5

    Nov 8, 2008, 01:12 AM
    Quote Originally Posted by SuryaGG View Post
    tkrussell,

    I am also looking for the answer to danar. The link in your reply does not discuss anything about DC (power system) short circuit current calculation.

    Hey guys the question above still stands!! Any suggestions??
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
    Uber Member
    		  
    #6

    Nov 8, 2008, 04:23 AM
    Try this:

    direct current DC arc

    And this:

    http://www.msha.gov/S&HINFO/TECHRPT/...L/INSTAN30.pdf
    rifky's Avatar
    rifky Posts: 1, Reputation: 1
    New Member
    		  
    #7

    Sep 22, 2011, 05:35 AM
    Guys, this might help.
    DC current increase can be analysed using exponetial method. Please see the graph in the attachment as well

    If a fault-short circuit develops, the current in the circuit increases exponentially, as shown in the Graph A. Mathematically, the current increase in the circuit can be written down by the following equation:
    I=IA • (1-e-(L/R)t)
    The value of available current IA, normally called expected current IP, is determined by the Ohms Law IA=U/R , but the value L/R= Τ is a time constant. The upper equation shows the L/R constant impact on the fusing time, where
    di/dt = U/L = IA / Τ
    Therefore, the higher the time constant L/R the lower the discharge di/dt and the longer the fusing phase.
    Graph B shows that due to lower inductance, current increases faster and the fusing time is shorter in comparison with the conditions in the Graph C, where an example of current increase at high time constant is presented.
    Attached Images
     
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