The loop Zi test (known here in Australia as fault loop impedance test) is used to determine the total impedance of the circuit from the supply transformer through your consumer main active, sub mains active, final sub sircuit active and back through your protective earths/neutrals to the transformer - which completes the loop. The purpose of this test is to ensure that the overall impedance of the fault current path is low enough such that it will allow enough current to flow and trip the circuit protective device before the cable and equipement is damaged
Electrician in South Africa here, Every chance I make, new socket install or move a light anything, I must compile a COC, Certificate of Compliance for the full home. If the owner has one I can add an amendment to it. Same as EU. If owner sells his home, and coc is older than 2 years he must get a new one. So not just inspector but every sparky MUST, have installation tester. Prove you did your work right and installation comply to building and Electrical regulation
Zi and Zc is for the maximum short circuit current which can be deliverd at your system. This have to higher than your switch off current of your fuse in x,xx seconds because otherwise your fuse/breaker wont work as fast as it has to be One of the features prevent tripping an earth fault breaker
