NCEES 530 (Calculate %Z)

[EEmarcus]

For this problem how is the percent z value calculated for the 40MVA system (Assuming the 1MVA Base)? The problem has .025 for the system impedance.

 

[EEmarcus]

I am attempting to solve this problem by the MVA method where...

SC TX= 1MVA/4%= 25MVA

SC Sys= 40MVA/4%= 1000MVA

SC Tot= (In Parallel) so answer is about 24.4MVA

Ssc= 24.4MVA/ (sqrt3*480)= 29,348A. ?????

NCEES Answer 18,500.

 

[Flyer_PE]

I think your answer will be found either here or here.

 

[EEmarcus]

Thanks Flyer PE!!! I get the PU Method now. In my error above they simplified the problem by directly giving us the SC of the system as 40MVA . Therefore the TX SC is (25MVA) and the system SC is (40MVA). It all works out now.

Couldn't find this problem using the search function.

 

[Flyer_PE]

^I had the advantage of knowing it was there before I started looking.

 

[knight1fox3]

Couldn't find this problem using the search function.

I also used to have troubles finding threads that already existed on NCEES problems using the EB.com search function. What I did to remedy this was to use G-o-o-g-l-e and type in for instance "NCEES 530" and the "engineerboards.com" after that and it would usually come up with a link to a thread on this site if one existed.

 

[majorever]

Thank you So much................this problem was bugging me about MVA method,  but this thread solved my problem.