Identifying HV Underground Cables

Do you have a clamp meter? or could you wind serveral turns of single wire around the cable then measure the voltage present across your makeshift winding.

The cable with no volts on the winding should be cold (i.e. not active).

What does your onsite documentation say? Your cabling "should" be labled.

That would nor work for a three phae cable. The net magnetic field is (should be)zero.

Assuming that the faulted cable is dead, disconnected, and accessible at both ends, then have a TDR (Time Domain Relectrometry) cable tester flown in, they're much easier to ship than a Thumper. Use it on both ends of your failed cable and you'll have a pretty good idea where to dig.

We already have TDR on site but it appears to totally inaccurate, even when tested on a drum of cable. I forget to mention that this cable run is about 5km long.

I guess it depends upon your sense of urgency. If I were in your position and didn't trust my instrument I would rent another one. If that's too costly then use the one you have and run the "Three Stake Test" from page 44 in this manual.

Is this one joint to effect the repair of the earth fault? If it is I'm afraid you will be sadly disappointed. You will need to chop about 10 / 15 yards out to be clear of any flash damage.

Well if you have it running at 80% load capacity a simple neodymium magnet on a string or in your finger tips will vibrate/hum with the AC current passing through the cable as their respective fields line up.

Low tech but very reliable for finding current flows with any moderate amperage behind them!

interesting answer ( and maybe safe enough if slinging the magnet under a bit of fishing line )

but i am curious if a strong magnet could create a hotspot or flash potential in a HV cable ?

I think in your situation I might be tempted to inject a Variable Isolated RF signal into the individual parts of both cables. you can vary the amplitude and use a hand held reciver to pick up the signal. You can then trace where the signal stops doing this will also pinpoint the place where the break is you do the same test from both ends to make sure.. no need to turn it off if you do it properly and carefully until you are ready to do the repair. I hope this helps you..

Dear Mr. merc600sec,

I have also faced a similar problem, but the distance was quite small and sorted out in 6 Hours.

Your suggestion is quite intresting, I have a doubt. Requesting you to provide some more details, perhaps, in your detail my doubt may get cleared.

Thanks,

DHAYANANDHAN.S

Dear Mr. philphy,

Pl. find out from the link below (taken from google search) and I find 5 methods which can be adopted and identify the cable which has the fault. Try which ever is possible by you. GOOD LUCK.

https://www.google.co.in/search?hl=en&newwindow=1&tbo=d&site=&source=hp&q=*locating+fault+in+underground++H.T.+cable*&oq=*locating+fault+in+underground++H.T.+cable*&gs_l=hp.3...14682.44787.0.46645.43.43.0.0.0.0.339.9348.7j1j34j1.43.0.les%3B..0.0...1c.1.pWXtGC40sng

Pl. copy and paste in the address bar.

Thanks, DHAYANANDHAN.S

Thanks for the help guys - the drama is solved. Just by pure chance we were investigating a washout and found the damage on the cable. Just the background first. We are located in a remote area in Indonesia. Cable theft is fairly common here. The damage was caused by a local finding the exposed cable and then hacking into it with a machete! No we haven't found the culprit. If he is still alive I would imagine at the very least he will need to change his underpants.

You could do it the old fashioned way and make a big water truck go over the area and then get a sacrificial victim to walk over the ground. He will locate the fault and you will know it.

You should ask him what flowers he likes before he starts walking.