We measure live to live with the circuit disconnected at the distribution board/ consumer unit.
But when we measure lives to earth the circuit protective conductor should be connected to the main earth terminal with all the installation earthing in place to hopefully pick up any earth fault between the lives and anything they may come into contact with that is or maybe close to earth potential.
If you see a YouTube video of a circuit being insulation tested with the lives and CPC all disconnected it is wrong, the CPC should be terminated into the earth bar with the tester clip attached to the earth bar or similar.
We measure live to live with the circuit disconnected at the distribution board/ consumer unit.
But when we measure lives to earth the circuit protective conductor should be connected to the main earth terminal with all the installation earthing in place to hopefully pick up any earth fault between the lives and anything they may come into contact with that is or maybe close to earth potential.
If you see a YouTube video of a circuit being insulation tested with the lives and CPC all disconnected it is wrong, the CPC should be terminated into the earth bar with the tester clip attached to the earth bar or similar.
