Arc Flash Calculation with only Max Fault Current

[Nardie]

So I have a new facility for R&D research that needs an arc flash calculation. The off-site utility provider has only provided the max fault current. From my understanding of IEEE 1584, an arc flash calculation needs to be performed using a max and min fault current. The on-site utility provider I have provides both the max and min fault currents at the 13.kV levels to perform an arc flash calculation. I use the ETAP software to perform the arc flash calculations. So, what do I need to do determine the min fault current? Thanks

 

[Master Nater]

eaton makes an easy and free fault current calculation app found on cell phone app store. it's worked great for me.

 

[D. Castor]

If you are taking service at medium voltage from a typical utility distribution feeder, the variation in fault current will be minimal, especially on the secondary side of your step down transformer. But you do have to consider other factors within your system that can change the available fault current. The most common is a local standby or emergency generator which will often produce much lower fault current than the utility source. Also portions of the system that may be normally supplied by a UPS, but can switch to utility power if the UPS fails.