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Tracing an underground cable fault?

alanblaby
Has anyone any experience of tracing an underground cable fault?

The cable supplies a private estates street lighting.

It's a 3 core 4mm SWA, approx. 50 metres in length, it has a Line to Earth fault.

I haven't separated the armour and internal earth core, so it could be a armour to Line cable fault, or a CPC to LIne fault. Either way the cable needs to be repaired.

We do not have drawings of where it runs, and from a site survey, it isnt obvious how it has been run either, logic would suggest it runs under the pavement, but a test digging yesterday at the first lamppost suggests it runs a direct route to its source across a garden.

I tested at both ends yesterday, it gave a wandering ~1600 ohms L-E reading, I was hoping the reading would be steady, then I could estimate where the fault was with the differing resisitance values from each end, but the reading was not steady at all - water ingress?

I did zap it a few times at 1000V insulation test, this made no difference, and, of course, gave a 0.00 Mohm reading.


Are there Companies with the equipment that is capable of tracing these faults?

We really don't want to dig up 50 metres of tarmaced pavement.
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  • 0
    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
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  • 0
    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
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