Ze derived from calculations to determine the Potential Short Circuit Current.

One method to determine the Potential short circuit current if you do not have a Loop Impedance Tester.
Find the volt drop of the system V1-V2 Divided by the Load gives Zs. Where V1 is the open circuit voltage,
V2 is the voltage under load and load is the amperage of the system.
IE: (V1)240 - (V2)238 = 2 divided by the Load 40Amps = 0.05 Ω.
Then PSC = System voltage (Uo) / (Zs) 240 ÷ 0.05 = 4800 Amp.
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