wa2ise regarding MI cable.

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Is this something that is obsolete, or is likely found in nuclear power plants or other exotic environments? Maybe a steel mill?

Not obsolete in the least.

It is commonly installed as feeders for emergency circuits.

I saw a good video of it under test, it survived a couple of hours directly in a large (huge) flame all the while it was still conducting power just fine.

Here is a photo of MI in a Hospital.

[Linked Image from nachi.org]

And here is a close up of the connectors

[Linked Image from nachi.org]

This is single conductor MI that is why you see it in groups of four phases A, B, C, and N.

The brass plate is needed to comply with 300.20(B).

Bob Badger
Construction & Maintenance Electrician
Massachusetts