Ideas for finding fault area in underground swa?

[HappyHippyDad]

Afternoon everyone..

During some testing I have found an IR reading of 0.01MΩ between N-E. This is on a length of SWA buried underground from the main consumer unit in the house to a garage consumer unit. The poor readings are not on the outgoing circuits in the garage.

There must be a join somewhere as it is T&E leaving the main CU and then SWA entering the garage CU. I cannot find this join.

The length of run is very approx 40m (as I don't know the course it takes underground). It is below many paving stones, and various other obstacles. It would cost a lot and cause major disruption to run a new cable so I am considering how to find the fault area. It's a difficult choice as it could takes days of fault finding and perhaps cause even more disruption than a planned route for a new cable.

One thought is to use an ezicat 100 cable finder to at least work out the route of the cable and then dig in certain areas (that are easier to get to). Then perhaps cut the cable and test both ends to see which I can keep in situ and which needs further investigation. I have never used an ezicat 100 before, are they reliable? Would this be a situation where it is the right tool for the job?

EziCAT 100 - Trent Hire and Sales

It detects alternating (AC) electromagnetic signals radiated due to currents flowing in conductive buried services. The operator is given the location and direction of the underground service when the unit receives reradiated radio frequencies through internal aerials, which detect the strength...

www.trenthireandsales.co.uk

Thanks all.

 

[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.