There has been quite a bit of discussion lately about utility short circuit data used in arc flash studies. There are many options such as using the data from the utility company without question, using a minimum value that may represent a a contingency such as a line or transformer out of service, using a maximum short circuit current from an infinite bus, or something else.

This week's question:

What short circuit source data do you use for the arc flash study?

• Whatever the utility provides
• Maximum/infinite bus
• Minimum/contingency case
• Maximum and minimum
• Something else

I use the utility value so far. If not available, there is a good paper from Eaton, attached.

Since I am in the utility I often get fault data at the substation, then model the distribution circuit. I usually will use plus or minus 10% for the scenarios and vary the line impedance by 10%.

It can take quite a while for us to model a system, depending on the number of projects we have going on, utility response, etc.
So, for starters we use an infinite bus, or utility data if available, for short circuit duty rating and submittal approval.
then, by the time the equipment is installed and the settings are ready, hopefully we have our Arcflash studies complete. That's the plan anyway. We've gotten bit on a few jobs needing to replace OCPDs to change the curves enough to lower the values to a more workable level.