LV Cables Fault Location

You might try this...

http://www.abb.com/cawp/seitp202/003a314df08e8aedc12578380056f1f3.aspx

....or Buy this setup, looks expensive, and learn how to use it..

http://www.tek.com/application/time-domain-reflectometry-tdr

You want the best and the cheapest solution to your problem. Have you ever heard the phrase, "You get what you paid for." Cheap is rarely the best solution and it is often the most expensive solution.

I did a brief search of XLPE/PVC cable types and none of the cables I found were rated for direct burial. So your one meter deep cables should be inside conduit of one type or another. So once your well paid, high skilled electrician/technician determines which cable has the short, this damaged cable can be used as a pull rope to replace the damaged cable with a new undamaged cable.

Now how your well paid electrician/technician will determine which cable has failed will change significantly depending on unstated conditions of your installation. The first thing I'd try is identifying the actual impedance of your short, it is not zero ohms. Your cable is not a super conductor.

Wait until dark, crank the power up to max and look for the glow.

Alternatively, pour salt water on the ground to saturate the wire run and, using a proper sensor (such as your tongue) search for the leak. This test can be performed at any time, day or night.

Hope this helps.

OK, this is a joke.

This guy might do it...cheap

THAT AIN'T NO GUY - SHE looks familiar, I got really, really drunk once and.........................Oh forget it

We have a saying in Arizona. Coyote Ugly!

Based on your initial comments - you are correct, zero means conductor insulation is faulted.

Isolate fault between point A and B perhaps between manholes or J-B's.

Pull faulty cable back with a pull line.

Pull in new conductors using pull line (that you attached to the faulty cable when you pulled it out), use lube, pull, trim, terminate, megger, and walk away.

There is no "cheap" solution, only the "correct" solution.

Pull in ground buried cable?

Your right, I should have read the post all the way through

I ASSumed buried in conduit.

Either way, if he could isolate the fault (won't be easy) he could replace the faulted section.

Raychem sells some great direct burial splice kits.

May be a water-diviner...?

Go to an electrical wholesaler and ask for a cable fault locator and they will advise you.

Another option is to approach an electrical services company in your area and they will do the job for you, that is a big cable .

JS

A TDR (time domain reflectometer) of some type is the instrument that will locate an impedance discontinuity in a transmission line and report the distance to fault. Solar Eagle also recommended this. Not so expensive but definitely not cheap (unless you can get to use one for mate's rates)

Now, before buying, renting or borrowing this instrument, conducting an investigation, scoping out a solution and mobilising a repair crew you want to be sure you really have a problem.

Are you sure it is a phase to ground fault and not a phase to neutral "fault"? Check if anybody has tapped into the energy path on the cable side of the isolation devices. Perhaps someone has "temporarily" connected a work lamp (airconditioner, whole household, small factory...) onto one phase of the cable/busbar in a transformer cabin or distribution board.

Are any protective devices tripping?

Here's really cheap....

Have you walked along the cable route yet.?

Look for disturbed soil or a conspicuously parked excavator......

Might be a backhoe fading problem.

Several points are not clear:

1. What length of cable are we talking about? Since you say LV, which I assume means Low Voltage, it presumably is a couple hundred meters or less.

2. I do understand that English is not your native language... You say "layed on Ground one meter deep". To me, "Laid on ground" means "on the surface" of the ground. Yet "one meter deep" means it is buried in the ground.

3. As several other posters have indicated, we don't know whether the cable is in a conduit or directly buried.

Again as several other posters have indicated,the correct solution is probably not cheap. The correct solution is new cable in an appropriate conduit.

What is this cable core earthing to? Is it wire armoured? Is it in a metal conduit? PVC insulated cable is not suitable for direct burying as someone has said.

You cannot get zero ohms through a cut in the PVC into damp soil. It will have a value. If it really is so low then something has hit it, look for new work, excavators, new posts in the ground.

"Phase to ground insulation is zero" has me confused, what is your ground? Is something tripping? If you can put a few hundred amps from a welder or a big truck battery across your fault you might hear a bang, or see some smoke coming up from the ground.

That's pretty cool.

Do you reckon you could hear an arc cracking that's buried 1 metre below the surface? How deep were the damaged conductors buried when you witnessed this technique?

The cost estimate you quoted is for the cheaper portable units right?

There are high end market electric fence units that will display a DTF (distance to fault) value. Which is handy for larger permanent installation's performance monitoring and trouble shooting. With these you wouldn't have to hear the crack.

GA by the way. I'll remember that technique.

Christle,I voted for you

In NZ we bury LV to a nominal 600mm. So even buried at that the depth the sound was audible. Don't know about 1000mm given that sound will be about 2.8dB down.

The fault locator must have a ground microphone like GM105 to hear the arcing.

JS

I've just realised that if he has a dead short, zero ohms, then it won't crackle from the conductor to whatever earth this guy has. Blow it first with my welder/battery solution, that will create a gap which will spark & crackle later with a cattle fence supply.

If the lines are buried you may as well replace all of them. What ever caused the one to fail (age of wire, manufacturing defect, moisture, rocks etc.) will most likely appear sooner or later in the other lines. We had a plant built in the 50's with lines in conduit and pull boxes. A main feed shorted out one cold wintery night. After working 4 days and nights moving snow and pulling wire we got it running again only to have another line fail about a month later