finding mains power cable

[THOMAS PATTON]

Hi all My extension to my 1974 bungalow is now on to phase 2 the weather in Scotland has been surprisingly dry but very windy. I am moving my electric meter and fuse box since it will be in the middle of the new bathroom. The Scottish Electricity man has been and advised me of the horrendous cost of moving the main power supply (between £1000-£1500)-but-apparently I can save some money if I can find the power cable on my property and they can break and reconnect power without digging up the road (£1000). Can anyone advise me on a meter I can hire that will detect my power cable it is 5 feet down at the meter but I suspect its only 2 feet at the public pathway by the road 20 metres from my front door. I hired a pulse meter the type that is about 21/2 feet long and send out a pulse? when you hold down a button--useless lots of false readings. many thanks Tom

[Dave]

You need a simple AC magnetometer to detect the leakage field, there are lots available; manufacturers include: Monitor Industries, Holaday - try a Google. You could also make your own with a search coil and amplifier. Alternatively, there's an outside chance that you may be able to pick-up something using a long wave radio if you've got some suitably "noisy" loads running. If it's a 3 phase feed you can increase the leakage field by loading-up just one phase.

Dave

[THOMAS PATTON]

Hi Dave I am looking for single phase 240 volt ac. How can I make "noise"in the supply-washing machine-cheap brushed drill-hover Flymo--allof them together?. Tom

[Michael Chare]

The plans/deeds of my property tell me the route of the electricity power supply.

I would have thought the Electricy Supply people would have had suitable equipment. - So that they can mend cables etc.

[THOMAS PATTON]

The electricity company have the plans on computer file mine s do nt show the power line.

Yup so would I but the power man had no suggestions Tom

[The Wanderer]

I reckon they're playing you for a sucker. Just had my main fuse and meter moved (East Anglia, EDF Energy). The guy who visited before they did the work, an estimator, had both Cat and Genny, and quickly pin-pointed my cable. When the jointer visited to actually do the work, I also happened to notice C&G in the back of his van.

Be warned, they will almost certainly try to charge you for work they may not carry out. I had a major battle with EDF who insisted I paid for them digging out a joint hole, instal a new piece of cable and main fuse, and make a joint on the service.

In my case the new position meant the actual cable length was reduced by a couple of metres. I'd already dug down and exposed the cable outside the property and upto the new entry duct.

I was in the industry for many years, and knew exactly what the jointer would do if he could. Remove the old main fuse, tape up the end of the cable, having made sure the neutral was shortened up by a few inches so there was no chance the phase and neutral could touch if the tape pulled off, pull the cable out from the old position and feed it to the new meter position.

In the end I got a refund of about £270 because the jointer had done exactly what I thought he'd do.

A couple of tips, ask them for a detailed explanation of the estimate. They should be able to break the work down into its various elements. Then check on the work when you have it done, and make sure they do carry out the work they're charging you for. If they manage to do it easier, ask for a refund.

[Dave]

Anything which generates RF noise, preferably old and without EMC suppression - or you could always remove the conducted EM filters. ... probably better to rent/make a search coil.

Dave

[john2]

Out of interest, I just tried this using a laptop on mains power as a noise source. I can detect the noise from the CU outside the house brick wall at the right height on long waves (150 kHz) but it fades out as soon as I move away from the wall, and there's very little coming from underground so I couldn't track the cable. An arc welder might be needed to get the noise level up a bit.

john2

[Dave Plowman (News)]

Would one of those treasure finder devices do it? I've never actually played with one.

[Dave]

I think these run at 10s of kHz and then beat the search oscillator against a reference oscilator - metal detunes the search oscillator slightly. If that's the case they probably have to have a fairly narrow bandpass filter so 50/100Hz would be filtered out. ... but that's all supposition so I may be wrong.

Dave

[Bob Eager]

Yup....there was a man outside our house last week using just such equipment, some spray paint and some natty stencils. He's marked out the

3phase and single phase cables all down the road opposite. Took him not long at all.

I wonder if you can hire those things? Or if they are on eBay?

[rrh]

Mine don't. They are EDF Energy - or rather one of their subcontractors - and my house is in North London. A subcontractor told me yesterday they'd just have to guess and dig carefully to find the incoming feed (knowing that gas, water and phone feeds are all in the same area).

This is all just so Siemens can fit a new meter, because the main fuse is stuck solid and can't be pulled. Given the trouble and expense of digging up the road, they will try again to pull the fuse and if necessary even change the whole service head (bit that incorporates the main fuse) live. All seems a bit low tech, health-and-safety unfriendly and unsophisticated to me, but there you are.

[Owain]

If the ones to your house are marked, get out and take some photos of the markings before the paint wears off.

I suspect most of the ones on Ebay are "fell out the back of a Transit, mate"

Owain

[Bob Eager]

Unfortunately not, or I would have!

Long as they weren't damaged by the fall! :-)

[Mogweed]

What you need is a Cable Avoidance Tool (CAT - like this one:

and possibly a signal generator. You can hire these from local tool hire shops (ours charges £30/day for the pair, cat & genny). It's many years since I used one (I was a cable jointer on BT before wrecking my back and being medically retired) so I'll not embarrass myself by trying to describe how to use it and then get it wrong :o) The hire shop should help you.

Mogweed.