What do you mean by Arc Flash? Is that a franchise name or a specialization I (apprentice) havent heard of?
Responsible companies in the US follow NFPA 70E which was created by OSHA in the late 70s. NFPA 70E defines an arc flash hazard as:
"A source of possible injury or damage to health associated with the release of energy caused by an electric arc."
The arc flash incident energy level is determined by calculating the available arcing fault current, then determining how long it takes for the upstream overcurrent protective device to operate.
There are a number of software packages that do the calculations, with input data being cables sizes and lengths, transformer sizes and impedance, Utility strength, etc.
Personal Protective Equipment is then selected based on the Incident Energy calculation.
Note that the more sophisticated protective devices have solid-state trip units that allow adjustments in Longtime Pickup, Long time delay, Short time pickup, Short time delay and Instantaneous. The software lets you to plot the devices on a Time Current Characteristic curve and make adjustments so that the device closest to the fault trips first.
Every electrical system with adjustable devices should have an analysis that provides settings for the relays and breakers. But it's often overlooked.