Can someone explain to me....?

[bruinfan]

When running the short-circuit analysis portion of the analysis, the program I am using shows a higher Isc current at a MCC bus then it does at the utility xfmr that is feeding this particular MCC. Can someone explain this to me?

Typically when I have done short circuit analysis by hand it has always been lower do to the distance between buses, equipment, etc. So, I am a little caught off guard here.

Thanks in advance for anyone's help!

[Ex twidget]

bruinfan-

Your motor contribution be offsetting the reduction in utility current from the impedance between the transformer and the MCC.

Try reducing motor contribution by taking them out of service or reducing the contribution to 0 cycles.

a hawksfan

[amohammed]

The bus you are referring to at the utility transformer: is it on the primary or the secondary side of the transformer?

[bruinfan]

It is on the secondary. The transformer feeds the MCC bus.

[haze10]

Motor contribution is highest at the MCC bus, because there is cable impedance to get back to the secondary xfrm terminals.