I need to work out the single phase fault level of a system which taps off from a 3 phase busbar with a fault level of 3.2kA. The 220V single phase power is taking from a phase and neutral and stepped down to 110V and the travels 5m and connects to a busbar. I am using the per unit method to work out 3 phase faults, can i use it to work out a single phase fault? and how?