What is this 1960's cable insulation made of?

[mxslick]

I'm more concerened that in pics 2 (and lower right corner in 3) there appears to be a lot of charring/smoke damage..did any of the gear fail violently in the past? Or is that why the OP is replacing the gear?

 

[ces]

as for meggering it, zog is of course correct on voltage, duration, and
resistance, but i think i'd try a test or two at closer to the working voltage
before i gave it the big zot!... no reason to create a short that leaves the
system unuseable.... if i got good readings on the lower voltage, then i'd
give the full voltage test.... if i got iffy readings..... well, time to reconsider.

like zog says, you're prolly gonna be fine.... i've seen 34.5 kv stuff with
carbon tracks all over the bus, and it meggered fine at 5 kv, and hipotted
fine at 50 kv, carbon tracks and all....
randy

Great ideas/cautions thanks we will definitely test at 500V first.

On Saturday we will confirm that this is copper or AL. It is incredibly light weight for copper.
There is asbestos all over this building so I would be surprised if it is in the insulation.

 

[ces]

I'm more concerened that in pics 2 (and lower right corner in 3) there appears to be a lot of charring/smoke damage..did any of the gear fail violently in the past? Or is that why the OP is replacing the gear?

Yes there are carbon signs of damage in many places. But I have not heard of any recent failures. As far as I know the reason to upgrade is to modernize to provide better spaces for tenants.
There are three 112.5kVA transformers for 135.000 sq.ft. which is surprising little in my experience. And these are very shallow nothing like we will be replacing them with in terms of size.

 

[ces]

update on 1960's building megger test

update on 1960's building megger test

Well you were right the cables are tin plated copper and not aluminum as the weight and flexibility of the conductors suggested to me at least. Must be quite a different alloy from what we have today.
Most of the readings (attached) were the meter maximum of 11G ohms on a Fluke 1507.

IEM the manufacturer tell me the board fault rating can be increased simply by having U.L. change the label (at what cost I wonder?) so if loads are reasonable we can keep the 2000A board but will be replacing all the distribution. I think someone here said they knew what these breakers were.

All of the cables are above grade without exception, perhaps this helped with what look to me like reasonable results although the dielectric absorption ratios are a bit low from what i understand.

Thank you again for the feedback and help in setting up this test.

 

[COFFEE TIME]

The Dept.of Energy would just yank it out along with the conduit,Not hoping for a good budget in 25 years.(and upgrade
all the way back to the substation).

i would agree.rip it out and take it to the scrap yard. also looking at pic#2 looks like a short before....

 

[weressl]

They have the appearance of craft-paper, rubber, cloth and cambric, an may not be listed in the insulation tables of the NEC any longer. As far as testing them there a few megger aficionados to you may get more accurate responses from here on the forum, that often frequent other rooms like say the NEC forum - title it "megger this..." and I'm sure they will be drawn like cats to a fish shack.

The rubber compounding chemistry of the 50's and 60's was rather unstable, so the outer warnished jute sock was there to make the wire slick for pulling but also to protect the rubber from deforming and to keep it in 'place' when it starts to develop cracks with aging. The cracks and carbonized dust is a slowly building disaster oppurtunity as it - with some atmospheric moisture - develops a high resistance conductive path to another similar void in a different phase that slowly heats up, arcs over and then extinguishes itself so you can't find where the fault was. Then the cycle starts over.

Megger will bring forth these weaknesses.