High Voltage Cable Fault Location Finding

CABLE FAULT LOCATION, CABLE THUMPERS ...

Cable Fault Locators - Thumpers - High Voltage, Inc.

Cable Fault Location Measuring Methods - HV ...

"As per vendor's reply, cable will not get damage during thumping."

If the cable manufacturer is happy with you using a thumper what's stopping you?
Any damage will occur at the point of the fault which I believe is what you're looking for.
Once located it is normal practice to remove several metres and insert two joints removeing the fault.

What I do find strange is a newly installed cable failing. The cable manufacturer would normally attend a fault like this as their reputation is on the line. Are you afraid they will find poor installation methods has caused the damage?

Yes, we are trying to locate the damage using thumper. But in process, we don't want to damage other cables, as 1 core cables are installed in trefoil formation.

These cables were already tested for Hipot during Factory and passed the tests. Hence from, vendor's point of view, it is either transportation or installation problem.

There may be a way, I do not know.

One approach would be to say 'Testing by Thumping may damage the other two cables', locate the fault, and go in prepared to repair three. (I am assuming the damage will occur at the same site.) That way if the other cables are damaged, at least you predicted it, and were prepared, and the finger points more at transportation than installation.

I'm sorry it's not a solution.

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Waty back when I did industrial experience in a coal mine there was a method used to detect insulation faults and broken conductor strands in trailing cables (1100V and 6600V).

They applied a DC Voltage to the cable and capacitor coupled one end to an amplifier with a headphone speaker set. When the cable was disturbed at the fault location, the movement created a noise on the DC voltage that was very detectable in the headphones.

The cables were also draped through a grounded trough of water. Any failures in insulation typically showed as a trail of bubbles as the cable moved through the water.

Probably not possible to test this way if already installed.

Suggest if the termination and jointing reviews are not conclusive, then the once off cost to remove and inspect the cable is worth the effort compared to future costs if the cable fails and causes serious outcomes.

SSKale, can u pls post a followup showing the result of the thumper test?

The IR test value was 450 Mohm, which is very excellent. Hence my interest in seeing the result of your thumper test.

One question: was that IR test at 11 KV?

Thank you for support everybody.

Today, we have tested 11kV cable by thumper. While thumping, at 9kV DC, fault happened again. Then, we walked along the cable route with audio detection device and finally we found the location of fault.

As seen in photo, cable is burned during thumping. But, we were fortunate that other cables were not harmed during thumping as cables in trefoil were not isolated.

This fault has happened in another plant substation, where contractor has dug the cables while doing some other civil work. Also, proper installation methods were not followed while soil backfiling. There was no gap between protection tile and cable.

Anyway, now we will install cable jointing kit at above location.

Thanks for the feedback. I appreciate that. Glad you found the fault.