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mrxphil
Active Contributor

Join Date: Mar 2011
Location: Lexington, Kentucky, United States of America
Posts: 20
Good Answers: 1

DC Voltage Levels for Testing MV Cable

09/15/2011 10:41 PM

I have two projects that I designed in NY and PA where the contractor is installing MV 8kV and 15kV cable, single conductors, shielded in aluminum trays. He is using 3M cold shrink kits for terminations, as directed. I want him to test the cable assembly with terminations completed, to ensure the whole assembly is valid before we throw the fire to it. He has asked for a test chart to record the data over time as well as the maximum DC voltage levels for the assembly. I know that the cable can withstand much more than the terminations, but not how much. If you have experience with Hi-pot testing and can help, it would be appreciated. I have contacted 3M but not heard back yet. Thanks / Phil

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 John 11:25
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VLF
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Join Date: Dec 2010
Posts: 3
#1

Re: DC Voltage Levels for Testing MV Cable

09/17/2011 2:15 AM

Do NOT Apply DC to a XLPE cable!! I assume it is XLPE cable? See previous post in this regard..... VLF is the way to do this. What does the manufacturer spec say?..... I think that the contractor does not know what he's doing, if he ask the client for the test spec...( I don't think the cable will work well with "FIRE" on it... rather switch on the breaker/close the link)!!
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manindra
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Join Date: Jun 2010
Location: Kolkata, West Bengal, India
Posts: 172
Good Answers: 1
#2

Re: DC Voltage Levels for Testing MV Cable

09/18/2011 1:35 AM

Insted of injecting DC high voltage ( which may develop TREE fault incase of XLPE cable) AC high voltage withstand test should be done. Also for condition monitoring of cable insulation, Insulation diagonistic tests like, PI,AI, DAR, DD, may be carried out.

Manindra

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 Manindra
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mrxphil
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Join Date: Mar 2011
Location: Lexington, Kentucky, United States of America
Posts: 20
Good Answers: 1
#3

Re: DC Voltage Levels for Testing MV Cable

09/18/2011 7:21 AM

I appreciate the comments from everyone. The insulation is not XLPE, in this case. The contractor is using Okonite cable, which is EPR. According to the manufacturer, this insulation can withstand high DC voltages. Their literature also warns against using DC hi pot testing on XLPE as well. I am having the contractor use the 3M termination recommendations for voltage levels, as these are the weakest link in the cable/termination assembly.

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 John 11:25
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