Hi
I have a earth fault on a customers drive with 30 drive over fittings.
The swa runs past each fitting and has a resin branch joint,with one cable going into fitting.
Have narrowed fault down to cable by dismantling fittings etc.
Is there any tester or method of measuring from the end of cable to fault.
We know the route of cable.
I relize I cold do the old dig cable
A suggestion on how to proceed building on Davesparks #3, Handysparks #9 and Spinlondons #10:
Call one end of cable 'Supply' and the other 'End'. Disconnect all lamp fittings first and both ends of cable.
Use an accurate dc ohmmeter - an instrument more precise than an MFT to take some resistance measurements as follows.
1. First confirm continuity of each of the conductors and the armouring too.
2. Measure L-N, L-E and N-E at Supply and End. Record measurements.
3. Connect L-N at each end and measure L-N at each of the 30 fittings. Record results.
4. Repeat 3 for L-E and then N-E.
5. Take some graph paper and mark off the x(horizontal axis) with a scale up to the length of the swa.
Mark of the y(vertical axis) with a scale up to the maximum resistance reading found in steps 3 and 4.
6. If you know the distances between each fitting then mark these along the x axis. (If you do not then I will provide a way to deal with that in another post.)
7. Plot the fitting readings from 3 and 4, using a different colour for each.
8. Join the points to create the curve of resistance for each of L-N, L-E and N-E.
9. You should see a smooth symmetrical curve with points lying on it. if you see a change in slope away from the expected smooth curve, this is where there will be near the discontinuity in the cable's characteristics, or in other words near the fault between conductors.
You might be able to narrow down to a stretch of cable between numbered fittings.
[Only a half an hour's thought gone in to this. But the principal is based on comparing a perfect cable's resistance properties to the faulty cable's. A prefect cable is symmetrical about its mid-point whereas a faulty cable is not. A big assumption is that for each conductor the joint box connections are all the same. ]