Earth faults are common fault condition in an electrical system. This will get noticed suddenly on a raining day. Once earth fault is detected it is Electrical Engineers headache to find the cause of earth fault. It can be a faulty device or a loose wire or wet terminal block. It is very important to locate the position of the earth fault and the reason for it.
In my experience it is easy to go from the higher end. Go to the main distribution board and switch off all loads on by one. When you switch off one load the earth fault indication will vanish. (If it is not vanishing after switching off all individual feeders then the cause can be inside the panel or there can be multiple faults. To locate multiple faults you have to switch off all feeders and switch on loads one by one).
About the mentioned way to locate the Earth Fault’s place, I have the following points :
1 – You don’t mention to the Earthing System, as with ” IT ” we use normally ” IMD equipments ” that locate the earth fault’s place.
2 – If we used the correct CB equipped with Earth Fault Protection that are chosen depending on the ” Earth Fault Protection Discrimination Study “, we can know directly at least the panel where this fault is occured, and by your way, we can locate the relevant outging.
3 – You said that the 1st earth fault should be cleared before the 2nd happen, that is 100% correct only in ” IT Earthing System “, but with other system ” TT, TN-S, TN-C “, each fault should be cleared as there’s no relation between 2 earth faults