Nitrogen Purging of Conductors

[iwire]

Has anyone done it or know about it?

I was asked to find out about it.

Apparently a new conductor Meged out poorly. The conductor manufacturer has suggested the conductor is wet and has recommended that the conductor have a 15 to 20 PSI supply of Nitrogen or Dry air applied at one end then let run 8 hours after all signs of moisture are gone.

Thanks in advance, Bob

 

[chris kennedy]

Never heard of that Bob but makes me wonder, THHN-THWN and which manufacturer?

 

[iwire]

Never heard of that Bob but makes me wonder, THHN-THWN and which manufacturer?

600 CU XHHW-2 VW-1 600 volt

"Service Wire Company"

 

[LarryFine]

The conductor manufacturer . . . has recommended that the conductor have a 15 to 20 PSI supply of Nitrogen or Dry air applied at one end then let run 8 hours after all signs of moisture are gone.

And then what? Do it every six months . . . forever? What's to keep the problem from recurring?

Do they mean inside the conductor's insulation (how?), or just flood the conduit with nitrogen?

I do know phone cables are pressurized with nitrogen. You may have seen gas bottles chained to phone poles.

To answer your first question: no.

 

[iwire]

And then what? Do it every six months . . . forever? What's to keep the problem from recurring?

It's brand new cable, never been energized, so nothing has happened to it yet.

Do they mean inside the conductor's insulation (how?),

Yes, I have a PDF that shows using a rubber hose that fits over the insulation and then using band clamps to seal it tight, the other end of the hose plumbed back to the nitrogen supply.

 

[KnobnTube]

Nitrogem can clear out the moisture

Nitrogem can clear out the moisture

It's brand new cable, never been energized, so nothing has happened to it yet.



Yes, I have a PDF that shows using a rubber hose that fits over the insulation and then using band clamps to seal it tight, the other end of the hose plumbed back to the nitrogen supply.

I was in industrial for 26 years. We had a similar situation with moisture in some 750mcm tray cable. We brought in a company who did the purging 0n 6 runs about 85ft each. They connected a shrink tube with fitting over the ends of each conductor and 1 over the overall sheath. Purged them overnight and all was well after.
That was in 1982 and everything was great and still operating well (I left in 2006. Never kNew what or why on the cable as it was delivered new to the site with sealed end caps. But, something??

 

[chris kennedy]

Yes, I have a PDF that shows using a rubber hose that fits over the insulation and then using band clamps to seal it tight, the other end of the hose plumbed back to the nitrogen supply.

I don't have that PDF.:smile:

 

[iwire]

I don't have that PDF.:smile:

Be glad to share it but I don't know how to post a pdf.

It's a small file.

 

[zog]

I have done N2 purges on MV cable, dont see why it wouldnt work on LV cable just as well. There is a procedure for doing it (IEEE-400 I think) and somewhere around here I have a video of the process.

The question is why is it bad? What were the test results and what method was used to perform these tests? Storage conditions? Is this the manufactures problem (Was it recieved this way). All these questions need to be answered before the N2 purge is discussed.

 

[don_resqcapt19]

The water inside of the conductor does not make it meg bad. It only becomes part of the conductor. It only megs bad when there is a problem with the insulation...maybe very very small holes that have enough water in them to give a poor meg reading. You may be able to drive the water out with nitrogen but that does not fix the problem with the insulation. There was a product has been used on medium voltage cables to force a silcone based insulating product through the cable to seal these types of holes. I think that problem was called "water treeing".

 

[iwire]

What were the test results

I don't know

and what method was used to perform these tests?

I don't know

Storage conditions?

I don't know

Is this the manufactures problem (Was it recieved this way).

I believe that is 'our' postion.

 

[iwire]

The water inside of the conductor does not make it meg bad. It only becomes part of the conductor.

Don that makes absolute sense to me, thank you.

The copper, wet or dry should still be insulated by the XHHW-2.

 

[electricalperson]

is the cable supposed to be pressurized with nitrogen or is it individual conductors inside conduit?

 

[iwire]

600 CU XHHW-2 VW-1 600 volt conductors in conduit

 

[electricalperson]

the cable must have a fault in it if your meggering it and getting a bad reading through XHHW. even if the cable is wet it should not megger bad since that insulation is rated for water

 

[winnie]

So conductors with wet rated insulation are giving a bad meg reading because the might be wet?

The only way that this makes sense is if there are different test conditions for dry versus wet conditions, and the conductors are not passing the dry condition values.

My (uneducated in this particular situation) preference would be to flood the conduit with water and see what it tests as.

-Jon

 

[zog]

The water inside of the conductor does not make it meg bad. It only becomes part of the conductor. It only megs bad when there is a problem with the insulation...maybe very very small holes that have enough water in them to give a poor meg reading. You may be able to drive the water out with nitrogen but that does not fix the problem with the insulation. There was a product has been used on medium voltage cables to force a silcone based insulating product through the cable to seal these types of holes. I think that problem was called "water treeing".

Water trees are usually found in XLPE type MV cables (Can be in any type) and lead to eletrical trees that quickly cause failures. There are several companies with this injection process with impressive data to back up thier claims of effectiveness (Some of which I have a lot of respect for) but some other "cable guys" I know say otherwise, I guess the jury is out and this type of process may be considered "life extension" process

 

[zog]

I don't know



I don't know



I don't know




I believe that is 'our' postion.

OK, I guess I wasnt much help there, how about this:, How confident are you in the capabilities of the company or person that did the testing?

 

[iwire]

Here is the pdf I received.

 

[wirenut1980]

Just a gut feeling here, but if this is new cable meggering bad, the manufacturer is trying to get off cheap by recommending this method instead of doing the right thing and replacing the cable free of charge. I think Don is on the right track.