Finding a fault in underground cable

reilig · 21-12-2013 05:27PM #1

Well one of the disadvantages to the mole plough is the way that it doesn't make the old man think before he puts it on the tractor. He mole ploughed a field and it appears that he went too deep and clipped the buried underground armoured cable which runs through the field for 200m between 2 sheds. It tripped the switch - but we don't know what part of the field he was in when he hit it. However, the switch will now stay up when reset - so it must have been a clean cut.

So far we have had a neighbour look at it who is a retired electrician. He has narrowed it down to being definitely in the 200m of cable between the sheds. We borrowed an electronic cable locator today, but hit a wall with it - it was supposed to find current - but even with the power off, it still buzzes when held over the cable. We thought it might be able to show us where the current stops in the cable, but this isn't working.

So have any of you budding electricians out there got a solution for us to find the fault or are we faced with replacing the whole length of cable?
I know we have a couple of electricians who contribute here?

moy83 · 21-12-2013 05:33PM

reilig wrote: »

Well one of the disadvantages to the mole plough is the way that it doesn't make the old man think before he puts it on the tractor. He mole ploughed a field and it appears that he went too deep and clipped the buried underground armoured cable which runs through the field for 200m between 2 sheds. It tripped the switch - but we don't know what part of the field he was in when he hit it. However, the switch will now stay up when reset - so it must have been a clean cut.

So far we have had a neighbour look at it who is a retired electrician. He has narrowed it down to being definitely in the 200m of cable between the sheds. We borrowed an electronic cable locator today, but hit a wall with it - it was supposed to find current - but even with the power off, it still buzzes when held over the cable. We thought it might be able to show us where the current stops in the cable, but this isn't working.

So have any of you budding electricians out there got a solution for us to find the fault or are we faced with replacing the whole length of cable?
I know we have a couple of electricians who contribute here?

Will it be ok to join underground when you do find it ? Also is there a chance he clipped it more than once ?
Id say you might be aswell digging where the plough was if you know the line of the cable

munkus · 21-12-2013 05:34PM

I know that there are Fluke testers that can do this for data cables, Cat5 and Cat6. As electricity travels at a constant speed through copper it should be able to test the return time and calculate the break distance.

Zr105 · 21-12-2013 06:09PM

munkus wrote: »

I know that there are Fluke testers that can do this for data cables, Cat5 and Cat6. As electricity travels at a constant speed through copper it should be able to test the return time and calculate the break distance.

Have heard of (and think i actually did some of the basics of it in college but dont remember any of it now) being done alright!

Also on the joining you can get a unit knicknamed a boat or a submarine, you make the joint inside the unit then mix up a 2 part resin and fill it up! Get it right though because there's no such thing as opening it back up!

bbam · 21-12-2013 06:34PM

moy83 wrote: »

Will it be ok to join underground when you do find it ? Also is there a chance he clipped it more than once ?
Id say you might be aswell digging where the plough was if you know the line of the cable

I'd probably agree with this..
Lad I work with did the same thing with the cable to the pumphouse.. After making two repairs and still no power they opened up a trench and laid a new cable in less time than it took to do the two unsuccessful repairs..

onyerbikepat · 21-12-2013 07:03PM

We had a similar problem a few years back. Shed is about 150 yards from supply in house and cable was laid with 3 underground joiners (not my decision). Had an idea where the cable was but no idea the number and location of joiners. The cable wasnt earthing though, unlike yours so we could detect power in the cable, with a wrap-around meter, I think. It was process of elimination after that. Kept eliminating 1/2 the cable with each hole dug. Took something like 6 holes.:D
Because you are earthing with the break you can't do this. We added a new joiner and drew up a proper map.

It may be possible to send a signal down the cable, even though it is earthing and detect it that way.
How many times did he cross over the cable?

Merida · 21-12-2013 07:51PM

If you have a cable locater or CAT as there known, you can get a genny to work with it, you'd have to disconnect the cable and connect the genny to it to send down a signal, the CAT has 3 different modes, turn it to genny and it will trace the cable exactly, this is how I find damaged cables or ducts.

reilig · 21-12-2013 09:18PM

Merida wrote: »

If you have a cable locater or CAT as there known, you can get a genny to work with it, you'd have to disconnect the cable and connect the genny to it to send down a signal, the CAT has 3 different modes, turn it to genny and it will trace the cable exactly, this is how I find damaged cables or ducts.

Thanks Merida,

Can you give me more info on the genny?

We have the cable locator (CAT) which has the 3 modes as you describe.

How does the genny send the signal?

freedominacup · 21-12-2013 09:23PM

reilig wrote: »

Thanks Merida,

Can you give me more info on the genny?

We have the cable locator (CAT) which has the 3 modes as you describe.

How does the genny send the signal?

It's not a genny in the sense of a petrol/diesel genny. This is the boy

http://www.cabledetection.co.uk/ezitrace

Hardly bigger than a radio.

locky76 · 21-12-2013 10:07PM

reilig wrote: »

Thanks Merida,
Can you give me more info on the genny?
We have the cable locator (CAT) which has the 3 modes as you describe.
How does the genny send the signal?

Ask a few local electricians as regards the genny, it's the cleanest way to do it when it works.
Your other alternative is a bit more primitive (but more successful imvho) is to expose the cable at halfway and see is there power there:
Yes- Go to 3/4 way and see if there is power there
No- Go to 1/4 way and see if there is power there
Keep repeating this and in a short time you will soon have it narrowed down to a few metres, I've PM'ed you my mobile if you need me to clarify it further...

dodod · 21-12-2013 10:12PM

I have one if you need a lend of it

Merida · 21-12-2013 10:26PM

The genny is a signal box that is compatable with the cat, it is battery operated. It has a plug with 2 cables out of it with clamps on the end, one is a live and the other an earth, plug cable into the genny, put the live clamp on copper of broken cable and put earth clamp on earthing rod that comes with genny and stick in ground. Turn on genny, turn cat to genny mode, it will be a different noise than if your tracing power. It is also important that your cat is calibrated, what part of the country you in?

reilig · 22-12-2013 08:27AM

Thanks Lads,

Merida, I'm in Leitrim. Some great info there.
Locky & Dodod, thanks for the offers, I'll let you know if I need them.
I spoke to the guy that I borrowed the CAT off last night and asked him about the Genny. He has one - it came with the CAT, but he has never used it. I'm going too get it off him tomorrow and give it a go, see what happens.

I'll let you know.

onyerbikepat · 22-12-2013 11:28AM

Can you detect the signal from above ground or do you have to dig and get at the cable?

Merida · 22-12-2013 12:51PM

onyerbikepat wrote: »

Can you detect the signal from above ground or do you have to dig and get at the cable?

The cable has to come out of ground somewhere, so in reiligs case its between 2 sheds, so disconnect it from switch or fuse board and connect genny. Once you connect genny and start sending signal, use the cat to trace, the signal will travel along broken cable, when you get to where cable is broken the cat will stop buzzing, has never let me down yet.

reilig · 13-01-2014 09:46AM

Just to follow up on this, we got the Cat and Genny on saturday and found where the cable was broken. Simple enough process when we managed to figure out how to use it properly. In fact, the old man had cut the cable in 2 places and the CAT and Genny found both of them. Savage job. Thanks for the advice lads!

Muckit · 13-01-2014 04:17PM

Excellent news. Great to know there's handy tools like that out there.

Did ye use a joiner box and that stuff that sets hard? I've heard about it but never used it. Is himself banned from tractor duty for a while?

On a separate topic, anyone know is there a yoke to check pipes for water leaks? Don't think I have any, but it would be handy if could check now and again. I seen teagasc Grange had them all over ground running along by fences

Conmaicne Mara · 13-01-2014 04:30PM

Muckit wrote: »

Don't think I have any

Recent photos would argue with that statement

Finding a fault in underground cable

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