I will preface my next statement with the disclaimer that I am not an engineer. But here goes, available fault current is partially determined by the total KVA of the transformers feeding the services. Obviously distance from the source and conductor size come into play. Lets say you are going to disconnect a single phase 120/208 service that feeds from a 3 phase overhead network. The network is fed by 5-3 phase banks of 225 KVA each and the banks are tied together at the secondaries with the standard malimiter fuses. Your service is 50 ft long and is # 2 stranded CU. What is the avaible fault current should a phase to phase flash occur.
If you look at NFPA 70e, within the first few pages, you will find that electric utilities are exempt so those regs. dont apply to me. OSHA 1910.269 apply and say I can wear 100% cotton. I am not required to wear FR by osha and I work on equipment with much higher available fault current that 120/240 house services. 70e is a little much, i would be wearing a full flash hood if 70e applied to me.