Assuming I have a grounded electrical device, for example a microwave. The left drawing shows that the phase wire is connected (due to a fault in the wire) to the microwave case, and an electrical path is created from the phase, to the case, and from there diverging to the human (displayed as a resistor) and to the grounding. The right image shows the equivalent circuit.
I couldn't understand however, how does the grounding helps reduce the current on the human? There is a voltage of Vphase on both the human and the resistor to the grounding (it is the equivalent resistance of the grounding wire). They are connected in parallel. It appears that the current on the human is Vphase/R_human whether the device is grounded or not. So how does the grounding help? Also, what is the potential of the case during regular times (I thought it it probably 0) and during faulty times (thought it is Vphase, beacuse now Vphase is directly connected to it) ?