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I have a five-conductor 2 AWG cable (three phases, neutral, and ground) connected into a 22.5 kVA (i.e., very big and dangerous) power supply. This is being used for research relating to ground faults, so the points at which the system is grounded are carefully controlled, and the ground wire is not connected to the power supply, though it does need to be present (even if it didn't, it's a five-conductor cable and we can't exactly pull one of the conductors out without unreasonable force that would risk damaging the other conductors).

So the question is this: how can I safely terminate this single 2 AWG wire in a manner that keeps it well-insulated from the power supply chassis? I was thinking of using a wire nut to just cap off the single wire, but there don't seem to be any designed to take a 2 AWG wire. Is there a keyword I can use to search for these?

Edit: also of note is that this is a ground wire and will be at ground potential, it just can't be connected to ground here. The other cables at the power supply output are carrying no more than 600 V (actually, the power supply might only go up to 500 V) so there's no high voltage that risks multi-centimeter arcs or corona discharge or anything.

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  • If its for research only (i.e. non-permanent installation), just wrap the end in electrical tape. Jun 22, 2018 at 21:16
  • @TomCarpenter This is for research, yes, but it's a permanent piece of apparatus that will be used for a variety of research over at least three years and probably much more, so it's probably best to treat it as a permanent installation.
    – Felthry
    Jun 22, 2018 at 21:22
  • Maybe a porcelain insulator? A picture of the cable installation would help.
    – Dejvid_no1
    Jun 22, 2018 at 21:23
  • @Dejvid_no1 I don't have a picture, unfortunately, but I can take one on monday if someone hasn't answered by then. Should have thought to take one earlier when I was on site.
    – Felthry
    Jun 22, 2018 at 21:25
  • This is the sort of question you should ask of a licensed electrician. I'm migrating this to DIY, which is where such people hang out.
    – Dave Tweed
    Jun 22, 2018 at 21:43

3 Answers 3

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Here is one possibility- "cold shrink" silicone insulator. Check the voltage rating for whatever type you are looking at.

You pull on the end of the coiled plastic and it unravels, leaving the silicone cap to shrink onto the end of the wire.

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  • Only rated for 1kV Jun 22, 2018 at 21:38
  • @TonyStewartEEsince1975 I don't see a voltage given, just a power. Okay, apparently it's effectively 600V so 1kV should be fine. Jun 22, 2018 at 21:48
  • Shielding Type Tape Shield, UniShield®, Wire Shield Shrink Ratio 2:1 Splice Type Cold Shrink Trademark 3M Voltage 1 kV Jun 22, 2018 at 21:51
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    @TonyStewartEEsince1975 OP's voltage is only 600V. It's 22kVA not 22kV. Jun 22, 2018 at 21:51
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    i see better now but lightning transients will not be withstood Jun 22, 2018 at 21:54
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There are standards in each country to follow, like using an interior or exterior junction box with a taped wirenut on wire.

If the warning label disappeared . Should someone guess if the loose live wire is live but looks dead? Who will know what ground fault tests may be done in future to induce a few kV transients to stress a possible loosened wirenut and short circuit creating an arc flash fire.

Don't do a Mickey Mouse job.

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At number 2 wire that is not live I would use super88 electrical tape. Industrial electricians use split bolts to join larger wires then a layer of cambric tape like 2520 then a layer of rubber tape 130c and finish off with super88. Some will use super33 but 88 is thicker and resist punctures better. Since the wire won't be used as a conductor the tape is a way of identifying it is not in use and will protect from any induced (phantom) voltage on the wire 480v phantom voltages can bite enough to wake you up with the right conditions. 480 being the standard in the U.S. for heavy industrial, I know there are voltages from 208-500 across the pond and super 88 will protect there also.

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