Underground cable fault locator

Try this site for Fault Location in Transmission Lines

This unit measures up to 200 km.

Thanks Bill but just checking the link..given by you..

http://www.hvtest.co.za/Company/PDF/Baur/IRG%203000.pdf

in this data sheet it says measuring range as 10m to 3 300 km.

(.) is missing as i doubt it could be 3,300 km.

cheers.

I suspect the range is 3,300 km. The surprise is the 10 m minimum -- I would have suspected it to be more. That unit uses TDR (time domain reflectometry) and high voltage pulses injected into an impedance, ideally matched to the characteristic impedance of the cable for maximum power transfer. The impedance range is from 12 ohms to 2000 ohms, which tells me that if your cable is 350 mcm or larger, its characteristic impedance will be less than 2000 ohms.

I have had the best luck with Megger test equipment..

http://www.megger.com/common/documents/PFL40_DS_en_V02.pdf

I have done it two ways:

1. Echo location, Send a pulse from a frequency generator, monitor with a scope (synched to the pulse) for the electronic echo, calculate the distance travelled and divide by 2 (signal has travelled to the break and back)

2. Using a test machine designed on a half wave bridge rectifier, where the cable Impedance of the cable is matched. The machine was specifically designed and calibrated for the cable.

here is a thought,maybe using an underground cable locator on the grounded phase the only problem is that it would have to be de-energized.you connect the cable locator to the grounded phase and when you lose the signal that should be where the fault is.in the 70's we used similar technology for finding telephone cable faults.interesting problem let me know how it works out.

Feed enough power to it and the fault will be under the new volcano you will have created...

Seriously, what kind of precision are you looking for? If you have junctions boxes here and there, Flow a small current to it from a low voltage transformer and use a current clamp to locate the defective segment.

Or use a DC source and divide the voltage by the current. Use the resistance with the cable ohm/Km to calculate the approximate distance. Don't forget to add the resistance of the main cable to the resistance of the ground conductor.

You might get different results if it is a dead short than if it is a high resistance short.

Good luck.

I used this brand of equipment when I worked for a power utility .

http://www.radiodetection.com/products.asp?sec_id=2689

Call the sales rep and ask for a demo. Various fault types require different equipment. Radio Detection seem sto have th ebroadest applicability. I used them all from a "thumper" to a Rycom, to TDR, Metrotech and even dowsing rods.

Good luck!

Noticed that your location is Saudi so the cable is probably under the sand between ends? A break of that magnitude may have left a mark on the surface or if you are really lucky you will find a very black JCB or a pair of smoking boots with a hacksaw next to them. Might be worth travelling the route and seeing if there has been any disturbance to the lie of the cable.

If you are using a high voltage tester such as a megger be very carefull to discharge the capacitance from the cable - I witnessed a near fatal accident where a technician went to unclip the megger after testing a 4km coax cable and received a 500V shock which left him unconcious for several minutes.

I am using cable fault locating instruments of Aplab make for power and telephone cables. When there was emergency the company used to do the fault locating with their staff and equipments. They are very fast and most accurate. They have helped me to locate cable fault in many occasions and can certify that they can locate any faults very close range of few feet accurately.i have purchased their equipments also.

You can see the details of their equipments in the following link :-

http://www.aplab.com/cfl/cfl02.htm

Their contact detail is :-

Tel. : 91-022-25821861 Fax : 91-022-25823137 Email : response@aplab.com .

If you want any more details about any model or immediate availability I can be of help to you. No busyness please. Only friendly gesture ( if you feel that you want any help).

Thanks everybody for the help. Thanks Abraham for your inputs.

We located the fault at 8km from the source. We used the ohm/km method (using wheatstone bridge).

No black JCB's or boots, or camels with missing legs... there was cable fault(most likely a manufacturing defect)

Cheers.

Can you disconnect power for a few minutes? I guess it is already disconnected...

If so look for a good TDR (Time Domain Reflectometer) It will give you the fault location in a matter of minutes...Tektronix makes excellent ones, And you can rent one for a day. some of them go as far as 30Km.

Wangito.