Fault Loop Impedance Calculator -

Draw a decision tree:

Cut to pocket size (~A6 or half A5). On site: fault loop impedance calculator

This "loop" starts at the point of the fault, travels down the protective conductor (earth wire) to the main earth terminal, through the transformer winding, and back along the phase conductor to the point of origin. Draw a decision tree: Cut to pocket size (~A6 or half A5)

$$Z_s = Z_e + (R_1 + R_2)$$ $$Z_s = 0.35 + 0.39 = 0.74 \Omega$$ through the transformer winding