Are fault current levels the same for each circuit?

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Fault current levels vary from one circuit to another because the amount of current that can flow during a short depends on the impedance in the path from the source to the fault. Each circuit presents a different impedance: the size and voltage of the source (transformers or feeders), the length and gauge of conductors, and any devices or protections in the circuit add resistance and reactance. Since the fault current roughly follows I = V / Z, higher impedance reduces the current, while lower impedance allows more current to flow. That means one circuit may experience a high short-circuit current while another, with longer runs or smaller conductors or fed from a different source, could have a much lower fault current. So, it’s not the same for every circuit.