Hi Forum
Im an EE at a smaller EE firm. We have SKM for arc flash evaluation (300 busses). I cant provide much detail for but we have a total system that main system that itself is about 50 bus points and 7 sub-systems (main switchboards and downstream each about 415 points each). How many buses do we need on our software package. Im thinking the 1000 bus package will be good enough. We can run the 7 sub systems separately and incorporate data as needed. Im inexperienced in this though.

What would you guys recommend? .
Thanks

I used the 300 bus version for a long time. I would break up big systems into smaller sub systems by substation. There would be 1 model that is the primary distribution system to the secondary of each substation then each substation would have its own file.

It can be a bit messy and motor contribution going from one sub to another was a trick but it worked. Now we use the 1000 bus version.

Guess what I'm saying is if you are a small firm, keep working around the limitations as long as you can before spending more $$. Just an opinion.

Thanks for the input JoeB

Breaking up the system is a solution, but it makes looking at different scenarios difficult. You need to run the main system to get the available fault at the point where subsystems connect. Then you use the results from the main system to get the source impedance for the subsystem. If you change scenarios so that the available fault at the subsystem connection point changes, then you need to run the subsystem with a different source impedance. You can't run SKM with multiple scenarios for the whole system to get the worst arc fault case automatically at each bus.

It can be done, and we have done it, but it is time consuming and you have to be careful to get things right. We developed an Excel spreadsheet that took results from different scenarios and found the worst case for each bus.

Thanks jghist