Short Circuit Fault Current (comprehensive)

Dear Sir,

I have attached a snapshot of small sld in which the equivalent parameters shown. If we calculate the equivalent impedance of cable-0022 manually and add that value with thevEq value of 11kv bus-1 that does not match with the shown value of 11kv bus-3. Kindly help and thanks in advance.

Yash Arora

asked 8/1/2015

1 Answer


It does look like something needs clarifying.  I get:

> c22=sqrt(0.0431^2+0.0270^2) = 0.0509
c22+1.3037 =  1.3546

1.3546 and not the 1.3335pu as expected.

Are you sure there are not some missing parallel impedance not shown on the diagram?  It may also be that we are adding the impedances arithmetically and not vectorially - do you have R and X for the 11 kV busbars so that we can check this. 

Other than the above, in this instance I would contact the software manufacturer and ask him why the results are not the same.  If you do this, please post his reply here for future reference. 



answered 8/2/2015 Steven McFadyen 246
Steven McFadyen
  • Dear Mr. Steven,
    Thanks for spending your precious time to reply. Actually, there is no parallel impedance which can impact on the calculated values in the SLD. And I don't have R & X values of 11kV busbar.

    - yash 8/2/2015

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