If you don't have a calculator handy, electricians often use a quick mental shortcut for standard 230V circuits with Type B breakers:
The total impedance of this loop determines the magnitude of the fault current. The loop consists of the following elements: The internal impedance of the supply transformer. Phase Conductor ( R1cap R sub 1 earth fault loop calculator
This estimates what the impedance should be based on the cable properties, before you measure it. If you don't have a calculator handy, electricians