33 KV Line

Use the correct test set. 5 KV test on a 33KV line and you get low results.

Get some one in that knows what they're doing, you don't!

Tony S, I sense dark Sarcasm in your post and I also feel you frothing in the mouth!

The only thing that is frothing around me is my glass of beer.

Be honest do you expect to get meaningful readings from a 5KV Megger?

Guru Ji, Please let me know what to use. I am being honest am looking for advise. No offence was intended. Regards

Do you have access to 56 / 36KV DC test equipment for line - line / line - earth testing. If not it's cheaper and safer to get a specialist company in to do the testing.

Kssoin, TonyS is correct - your next step is to test with equipment that provides a voltage at approximately the operating voltage of your line. The likely culprit is a surge arrester or insulator that has a defect or damage of some sort. It is capable of sustaining the 5kV DC of your megger, but when the voltage is raised to operating leve, it flashes over and trips.

The original cause may have been something that shorted phase-to-phase and to ground, and damaged the insulator or arrester. You didn't say if this is an overhead line. Do you have large birds that tend to roost on poles, or large varmints (raccoons, etc.) that could climb a pole? Have you done a close visual inspection using binoculars to see if you notice any burn marks, or a dead animal around the base of a pole?

If it is underground, then you need to check any places where the line surfaces (padmount switches or transformers, pole risers, etc.). Also, if you have a relatively higher impedance fault than can show on your megger, you may need to use a cable thumper/burner to force the short to low-impedance and to help locate it.

You will need to get a professional testing company in to look at your problem if you aren't able to do any of these.

Peter T is dam right in his recommendation. I was maintaining a similar 22 KM 33 kV OH line which was our own distribution system. Similar earth fault occurred due to cracked insulators which could not be found on normal megger test. I used to apply a HV puncturing and there after I could locate the faulty insulator by line petrolling. The lightening protector after a discharge after heavy lightening will show similar results and can be confirmed after disconnecting them and switching on the line. Under faulty conditions the lines should not be charged repeatedly as it can damage the breaker itself.

Since our line was passing through forest area often monkey fault and snake fault occur at times ( both of them are instantaneous earth fault which re occur ). So line petrolling is essential to locate such earth faults. In case of UG cable the end termination is another such culprit where the Megger test fails.

We have a 80Kv Pressure test set in the store...you are welcome to use it to locate the fault

Phase to phase fault may be clashing conductors

Phase to earth fault may be pin insulators that needs to be changed...could also be a tree in the line...or birds making their nest on the structure....

They guys must drive and inspect the line