Ideas for finding fault area in underground swa?

[HappyHippyDad]

Well, I have a bit to think about then!

My gut feeling is it would just be better to run a new cable, but it is such a difficult run to make neat and it is a very well kept garden/grounds. It would be good to at least use some of the existing buried SWA, the majority of which is likely to be absolutely fine.

A dilemma.

Thanks for all the replies.

 

[timhoward]

In terms of finding the cable route - I've had very good success with this relatively inexpensive tool:

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I had a silly situation once where I had to prove to the DNO that a bungalow wasn't fed from a substation on the private estate. Using one of those I traced the supply cable underground, under a boundary wall and to the middle of a road using one of those. I could even pick up the signal at the nearest neighbours cut-out, proving they were on the same phase.
You'd need one core connected to live, and the tool connected to that core and the earth stake it comes with.

 

[littlespark]

Have you tried two bits of bent fence wire held loosely in your closed hands?

 

[littlespark]

Have you tried two bits of bent fence wire held loosely in your closed hands?

You might laugh..... but on the caravan site, that was more reliable at finding cables than our Ezicat... (something else i wish i'd "squirrelled away" when we sold up)

Considering the Ezicat is designed for cable avoidance and not cable finding.... And our cables, drains and water pipes tend to utilise the same trenches.

 

[Lucien Nunes]

A loop / bridge test will probably find the fault. TDR will probably find the joint and/or the fault if they are in different places. You might recall my Heath Robinson TDR setup that I wrote a thread about, using my laptop and an external VGA monitor when I didn't have an actual TDR instrument available, which was capable of locating a fault to within a metre or two. I'd still use that method now, or at least try wielding some technology at it first before digging randomly along the route.

You mention the IR reading as '0.01MΩ' which covers a multitude of sins as it's effectively off the scale of the IR tester. If the resolution of that range is 0.01MΩ and it's allowed +/- 1 count, that could be anything between 0Ω and 15,000Ω. A continuity reading that gives more figures would help characterise the fault.

 

[OnlQQker]

Overhead?

Speak to anybody that’s dug up the ground for water mains…. They probably nicked the cable with a digger bucket

If the SWA cable was steel armored, I have pulled an extremely long cable out of the ground with a mini digger.
The problem would be connecting the new cable to the old cable so it could be pulled through without breaking.
You can make a good connection between the L/N/E but that is not good enough, you would need a 2 part epoxy resin for metal and using the section of 400 mm outer sheath swa cable, cut a 20mm section slit out all of the way down the 400mm piece so you could apply the resin.

That holds it, all you need then is a mini digger one end

 

[LewisM]

We use TDRs all the time at work and they work quite well however without a reference of where the cables run you'll still be guessing where to dig

 

[Simon47]

Ps, just for reference , If you see any watermains people, (not going to mention names) but the guys digging up the watermains.

It's worth chatting to them because they'll mole it for you, a lot cheaper and quicker than you think.

Ha ha, I like the way the mole appeared right on cue in the right place. It might work in some soils, but around here it could go anywhere after it's been diverted by a rock, or two, or three, or ...
I remember a few years ago I was doing a network install for a client on a new development. Outside there was a guy trying to mole across the site access road - it wasn't fully surfaced, but he was trying not to disturb what was down. When I was leaving, he was digging a hole hoping to find his mole which hadn't gone straight across as it was supposed to.