Whilst these methods are technically valid the amount of set up and control required to perform them in a practical situation is overwhelming.
"Ahh Mr. customer you have a fault in your lighting circuit, let me just run a few extra cables around your house, set up a fairly sensitive electronic circuit and program my spreadsheet for the calculation, I should only be half a day or so."
"But, but the wires are hanging out of the light fitting over there, is this not a good sign of a fault?"
Where you have a single cable of known length and a known type of fault of negligible impedance then the operation could be undertaken. It is most likely to apply to long lengths of underground cable feeding sub mains and the like where the cost of ground excavation may be excessive and getting the most precise location is then required.
In a basic situation where there are many joints in a circuit cable and the resistance of the fault is unknown then the methods would only provide a very approximate measure of the fault location.
