Tracing an underground cable fault?

I had just this problem many years ago in a 3rd world country. The fault was intermittent which I solved by putting 2 electrodes in a bath of slightly salty water in series so that the fault kept occurring but the breaker didn't trip.

Once I had a decent short circuit, I fed a known current down the cable to the fault and used the remaining length of the faulty core and a good core connected in series as a voltmeter lead to measure the volt drop from source to fault.

This gave a remarkably accurate location which turned out to be in a duct under a road so it must have been a manufacturing fault.

Think far more specific, walking backwards and forwards across a five acre field pushing in markers that form a nice straight line to reveal where the water pipe is buried.


Andy B.

Dowsing rods usually "work" due to the ideomotor effect: they all rely on a mechanism which amplifies any subtle movement of the hands. Thus they move either because of subconscious changes of grip tension/angle etc, or due to external factors such as a slight change of incline of the ground.


Beyond that, you can debate to what extent such factors give good results, and to what extent it's luck / confirmation bias etc - e.g. the fact that England is a wet place and and if you pick any random spot there's a good chance there's water underneath.


James "The Amazing" Randi conducted a controlled experiment where a parallel run  of water pipes was buried, and one pipe at a time was randomly chosen to have water running though it. A group of dowsers all failed to do better than chance.

Fifty years ago, when I was in my early teens, my dad was trying to locate a water pipe along with a guy from the water board who told my dad that he should not dabble in witchcraft.


I have not got a clue how it works, but it does. These rods are a bit flashy, I always used some bent wire or the like, but last year coming home from a job and stopped at the Rollright Stones and met Ron who lent me a set of rods to try in the stone circle, then proceeded to sell me these rods.


One impressive bit of dowsing was when i worked on a new housing site where the groundworkers laid the tarmac over the water meter covers in the footway, after his initial disbelief was dispelled the assistant agent walked down the footway with me and we marked all the service runs then tapped the tarmac and found the water meters for around twenty houses.


Ignore the people who kick up a fuss about people dowsing for service pipes and cables, just because they cannot find a rationale explanation for it working doesn’t mean that it doesn’t work.


I have had a few conversations with dowsers who claim they can dowse a map drawn on paper and the like, I can’t accept that works, but where there is a pipe or cable buried in the ground it usually works quite well.


Andy Betteridge

Reminds me years ago my dad was making holes for a new fence at the school were he worked and one of the boys from the school came to ask my dad why none of the lights in the school were working  turns out he'd gone through a 3 phase cable that supplied a group of the port classrooms that were more or less permenant the thing was my dad didn't here a bang or even feel a tingle despite making the holes with an iron bar

As a follow up to this, it has gone to the Boss to make the decision on what to do now, I've said there may be Companies available to search the route, and possibly trace the fault area. With many Companies shut down at the moment, he isnt making it a priority.

Further testing was carried out, the armour has shorted to the blue and red cores, with a resistance of around 1300 ohms when it was tested last, the red and blue cores have negligible resistance, <1 ohm to each other, but annoyingly, it wavers, and isnt very different whichever end it is tested from. Even if we did test and find a rough length of the fault, we don't know the route, so it would be fruitless in digging random holes. The yellow core is not damaged.

Thanks for all the pointers for help.

Alan Capon:
AncientMariner:

. . . Can you see any signs of severe gardening having taken place, not only along the "obvious" route, but also in the vicinity or close by elsewhere?

New fence posts are always a possibility. It is surprising the damage you can do with a Metpost! 

Regards,

Alan. 

Or a water meter!


Our next door neighbours new water meter was grand for a few months and then Christmas Eve or the day before(?) The nick in the PILC street cable must have let some water in and it went dark!  For some months actually, since it was a 5-core main cable which included the street light's live supply.  Since SP don't replace like for like corewise, a new feed had to be supplied to the street light opposite.

Clive