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Utility Modeling for arc Flash study

Discussion in 'NESC - ANSI C2 - National Electrical Safety Code' started by Sujit, Mar 27, 2008.

  1. Sujit New Member

    hi friends,
    i am on the job of Arc Flash study of 1 industrial setup.
    The given fault values contains max & min values & cooorosponding X/R ratio as mentioned below:

    Utility Fault levels are given with following details:
    Supply voltage : 440V Freq:50 hz

    Utility Fault level :
    3 phase :- Max : 13kA , Min : 8.6kA
    1 phase :- Max : 8.8kA , Min :1.9kA

    X/R Ratio :
    3 phase :- Max : 3.62 , Min : 0.329
    1 phase :- Max : 3.31 , Min : 0.22

    So, my questions is, how to model the utility for Arc Flash studies?

    Is it required to model two utilities with 1 with max fault level & 1 with min fault level & corrosponding X/R ratio ; one is operating at a time.

    Please advise?
    Sujit, Mar 27, 2008
    #1

  2. Homerjs78 New Member

    Your software may allow you to model the system for both scenarios without requiring you to model the system twice. If you use the IEEE 1584 equations, there is a built in (reduced fault current) check that will evaluate 100% and 85% of fault current. If you model both the high and low estimate at both 100% and 85%, you will have a sufficient analysis. I don’t know if this is an option in all available software packages but this is an option in the Easy Power software.
    Homerjs78, Mar 28, 2008
    #2

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