aluminum to copper connection at CB 2

[OffTap2020]

Does anyone have a suggestion regarding this..?

1590 acsr taps from 16kv isolation switch to bushing connectors at top of outdoor vacuum CB.

The old isolation switches have copper "pads", not tinned or bronzed. The 1590 lugs are all aluminum. The existing connection was made up with similar parts, but with a 1/16" of an inch of "tinned" copper between copper switch pad and aluminum connector.( Basically a thin square sheet of tinned copper) The existing tinned copper is not large enough in diameter to be used again, due to the size of the new style of aluminum connector.

Am I making way to big of a deal about the aluminum to copper connection? Or does anyone have a cost effective idea to join these?

Offtap

 

[Laplacian]

No, you are not making too big a deal about it. You will get aluminum oxide building up between the joint and pushing the two pads apart. The bolts will end up carrying all the current.

Hubble has a NEMA 4-hole transition plate about 1/16" thick. It has a copper side and an aluminum side (80% aluminum, 20% copper) that is molecularly bonded and will cost approximately $5 US per plate.

I can look the part number up tomorrow if you can't find it. I believe the part number started with TPS.

 

[OffTap2020]

Laplacian,
Yes, that is exactly what I'm looking for. So far, I have not been able to find them on the Hubbell site, but I will continue looking.
I hope they are available in less then the usual " 8-12 weeks" we've been dealing with lately.

OffTap

 

[Laplacian]

I found it. Go to

http://www.hubbellpowersystems.com/powertest/catalog_sections/cat_sec_connector.html

and scroll down to "Substation" and click the *.pdf link to section "SF". The TP plates are on page SF-11. Sounds like you may need the TPD plate. They are most likely not a stock item and may be a few week delivery. Call your local Hubbell supplier and ask.

 

[LMBT]

See page 11 of the following file:

http://www.hubbellpowersystems.com/powertest/view/download.asp?pubID=145

 

[jghrist]

Transition plates are not always used. You can make reliable copper pad to aluminum pad connections if you follow the proper procedures. See

http://www.hubbellpowersystems.com/powertest/tips_news/pdfs_best/A9605.pdf

 

[stevenal]

A transition plate makes one connection (and the possible failure point)into two. I would tin the copper pads, use non-gritted oxide inhibiter, torque the connections properly, use belville washers, and make sure the aluminum is not directly below the copper.

 

[OffTap2020]

Stevenal,

Which part of the transition piece do you feel increases the possibility of a failure? Is it the molecular bonding of the copper and aluminum plate? Or do you mean that 1 connection is better then 2?

Removing the (3) 3000 amp switches from the rack and sending them out to be plated is not an option on this project. Personally I wish they would have included in the budget 3 NEW switches but....

OffTap

 

[jghrist]

If you are worried about the aluminum to copper connection, why not use copper conductors? The CB bushings will have copper threaded studs and probably copper or tinned copper stud connectors. Copper conductors would eliminate all bimetallic connections.

 

[stevenal]

offtap,

I don't count the transition within the plate, just the additional mechanical connection involved. Inserting an additional piece makes one connection into two, doubling the chances of failure at that point.

No need to send the switch anywhere. Use a torch, solder, and flux. Maybe not as good as a factory hot dip, but better than none.

 

[steelerfan28655]

Could you use a Burndy Substation connector #NAR48A-4N. It is designed to connect aluminum or copper cable to aluminum or coppar plate?

I have this problem all the time with regulators and breakers that have been purchased over the last 30 or so years. None of them have the same type of connections, some are copper, some bronze, some threaded post others have smooth post or flat pad.


Happiness is a way of travel, not a destination.

 

[OffTap2020]

Steelerfan,
Yes, we've used those in the past, on some of our smaller ocb's that were less then 600amp.

Unfortunetly, this CB requires parallel taps of 1590 ACSR or AAC. Might be tougher to make those connectors work.

I ordered the transition pads from Hubbell, and received them already. Gonna install them this sunday, only time the load is low enough to perform the switching.

OffTap

 

[scottf]

Does the plate just fit between the existing connections?, e.g. it doesn't introduce an additional connection...still one set of nuts and bolts.

 

[OffTap2020]

Only one set of nuts and bolts. Total.

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