Testing Medium Voltage Cable

[spsnyder]

What is a good standard for determining what type of test for medium voltage cable? I was looking at NETA's Standard for Maintenance Testing Specification 2007 Edition. Here's the details...

Want to learn what test (if any) would give insite into the condition of 40 yr old medium voltage (13.8 kV system) and how destructive the test is. The cable is paper insulated lead covered (PILC). The paper is impregnated with oil, which has leaked out in some splices in the past.

Thank you for your help.

 

[zog]

IEEE std 400 is the most commonly referenced standard for MV cable testing. IEEE 576 covers more installation type issues.

NETA, IEEE 400, IEEE 576, ICEA all agree that DC testing of service aged insulated cables (>5 years in service) should be considered a destructive test. Basically if the test fails you have damaged you cable.

The 3 best methods today are VLF, Tan Delta, and PD testing.

The method that is best for your cables depends on why you are testing them and if you can shut down to test.

You mentioned you wanted to know the condition of the cables, so you want either a PD or Tan Delta test as they are condition assesment tests.

If you have many splices or different dielectrics the PD test may give "sketchy" data.

So that leaves Tan Delta, which requires a shut down but can give you condition assement of your old cables while not damaging your cables. Condition assement allows you to priortize which cables should be replaced first.

Disclaimer to all who will argue this post: I am not saying that Tan Delta is the best cable test method, I am saying from the info provided by the OP Tan Delta seems to be the best for his situation.

 

[spsnyder]

Zog,

Thank you very much for the information. IEEE 400 is titled Guide to Field Testing of Laminated Dialectric ... with High Direct Current Voltage." Does the standard describe when to use this test, or just how to perform test? From what I have read from Zog and other sources "High Pot" tests are not for any cables with any age. Why is the test not destructive to new cables? I assume it is meant to detect manufacturing defects.

IEEE 576 seems to be the standard I should look at. Thank you Zog.

I agree that the Tan Delta test is most appropriate for our situation. I read an article from NETA that said that as well. Thanks.

 

[zog]

"Why is the test not destructive to new cables? I assume it is meant to detect manufacturing defects"

you are correct. It is meant to find defects and installation issues, DC test will still stress the insulation of a new cable but there SHOULD not be much leakage on a new cable so the damage is minimized.

P.S. I think you may have an old copy of the IEEE 400 the 2001 version is titled "Guide for Field Testing and Evaluation of the Insulation of Shielded Power Cable Systems"