Megger test 1/C, 600V cable still on the reel (using Fluke 1587 at 1000VDC)

D

Dale001289

Senior Member
Location
Georgia
Has anyone ever performed a megger test for single conductor copper cable 500kCMIL, 600V XHHW-2 unshielded that was still on the reel from the factory? How would you safe-off the opposite end?
 
don_resqcapt19 said:
Pretty much a worthless test...where is the path for current to flow. Even a big chunk of missing insulation will likely show infinity on a megger.
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Might soak or submerge the reel, but even then it would be sketchy readings. Back in the 80’s we were buying Canadian wire, and had several rolls of 500 copper that had gashes halfway into the roll. Unfortunately ( maybe actually fortunately) we found it halfway into a several hundred foot pull.
 
kwired said:
You will put one test lead on the cut end of the conductor and the other lead on the wood/plastic reel?
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Maybe if bare copper was touching the wood. Even with a gouge in the insulation next to the wood, I don't think you would get anything other than infinity.
 
I get this question all the time. This is marketing smoke and mirrors. The only way to test an unsheilded cable on site is to dunk it into a tank of water where that water acts as the second conductive plane between the metal conductor and the insulation. The gold standard for this is the ANSI/NETA- ATS. That will force you to table 100.1 for test values, but the notes will also tell you it's not a pass or fail test, rather a data point for trending analysis. Keeping in mind, trending means lots of tests and each one must be done at the same temp, humidity and test set up, which is basically impossible to do. Thus smoke and mirrors. Same rules apply even after it's installed. Testing conductor to conductor or to the metal conduit won't provide a single result either, only a data point for trending. Sheilded cables are a different story and it is good for that, but unsheilded cables it's really a foolish test. You're better off just ohming it out. Often the engineer will want it because it's the only thing they can ask for even though it won't provide any meaningul results. When the cable is actually made, it does go through what we call a "spark test". The cable runs through a curtain of high DC voltage where if the insulation is too thin, it should "pop" and stop the line or alarm out. But that won't tell you if anything happended after it was made. There is an international manufacturer currently developing a non-destructive hi-pot test that will tell you if an unsheilded cable is good or bad but that's still in the works and not available yet. It is available for MV sheilded cables not just not LV unsheilded ones. Once that is available it will make insulation resistance tests of these types of wires obsolete.
 
hillbilly1 said:
Might soak or submerge the reel, but even then it would be sketchy readings. Back in the 80’s we were buying Canadian wire, and had several rolls of 500 copper that had gashes halfway into the roll. Unfortunately ( maybe actually fortunately) we found it halfway into a several hundred foot pull.
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We didn’t catch some on an underground pull. Three years later the #2 Al failed. I personally let every foot slide thru my hands with the replacement. Caught several insulation deformities. Scotchkote, tape, Scotchkote.
 
Boingo1972 said:
Same rules apply even after it's installed. Testing conductor to conductor or to the metal conduit won't provide a single result either,
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Yep, without something conductive between the conductor and the metal conduit, a megger doesn't tell you much of anything. Most of the time, if I was using a megger it was part of the troubleshooting process.
 
ptonsparky said:
We didn’t catch some on an underground pull. Three years later the #2 Al failed. I personally let every foot slide thru my hands with the replacement. Caught several insulation deformities. Scotchkote, tape, Scotchkote.
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That possibly long time for aluminum underground, or the inside of pipe remained very dry.

I've buried pipe on a Friday on hot/humid day and pulled conductor on Monday and pull rope already wicked up some moisture.
 
ptonsparky said:
We didn’t catch some on an underground pull. Three years later the #2 Al failed. I personally let every foot slide thru my hands with the replacement. Caught several insulation deformities. Scotchkote, tape, Scotchkote.
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I had some recently from the supply house (for my own brand new garage) 1/0 that had a couple of gashes. Supply house said it must have been damaged from the factory. I asked them why it had black tape on the damage then. They got real silent. I made it very clear that the warehouse guys knew they damaged it and tried to hide it on black insulation. Switched supply houses the following week. Love the new one and never looked back. I'm big on integrity. I probably would have used the cut pieces for a 15-20% discount if they had just been up front with me about it.

Mark
 
We didn't monitor it on the first pull or we would have noticed what looked like a forklift gash in the insulation.
busman said:
I had some recently from the supply house (for my own brand new garage) 1/0 that had a couple of gashes. Supply house said it must have been damaged from the factory. I asked them why it had black tape on the damage then. They got real silent. I made it very clear that the warehouse guys knew they damaged it and tried to hide it on black insulation. Switched supply houses the following week. Love the new one and never looked back. I'm big on integrity. I probably would have used the cut pieces for a 15-20% discount if they had just been up front with me about it.

Mark
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