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#182850 - 12/13/08 06:27 PM Sodium cables
Albert Offline
Member
Registered: 08/16/06
Posts: 76
Loc: Falls Church, VA
One of the oddest electrical technologies of the past is the sodium cable. As the name indicates, it's an insulated power cable with metallic sodium as a conductor, in place of the usual copper or aluminum. Apparently it was "the next big thing" for a while in the 1960s, but as far as I know, it never caught on - though it probably "caught fire" a few times!

On pages 24-26 of this presentation, there's information about sodium cables and a cutaway photo of
one:
http://www.ewh.ieee.org/soc/pes/icc/subcommittees/subcom_e/E4/2005/8Hans.pdf

The entire presentation is quite interesting; check out the "Blues Brothers" on page 19.

Alber
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#182852 - 12/13/08 07:03 PM Re: Sodium cables [Re: Albert]
NJwirenut Offline
Member
Registered: 09/15/01
Posts: 806
Loc: Bergen County, NJ
Interesting stuff!

How would you make a reliable electrical connection to a sodium conductor? Sodium is so soft that it makes the "cold flow" problems of aluminum look like nothing. I can't see how any kind of crimp or mechanical lug is going to stay tight.

Then there's the whole "reacts explosively with water" thing...
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#182853 - 12/13/08 08:02 PM Re: Sodium cables [Re: NJwirenut]
Albert Offline
Member
Registered: 08/16/06
Posts: 76
Loc: Falls Church, VA
Yes, terminations must have been a major problem. The only thing I've seen in that regard is a reference to threaded connectors; I suppose they used some kind of lug that was screwed onto the exposed conductor. But it must have been difficult to come up with a design that could be screwed on tightly enough to make a good connection while not breaking the conductor.

It's really incredible that such a technology could actually have been approved and deployed by utilities. Apparently its only advantage was cost savings; surprisingly (to me) sodium was cheaper than copper and aluminum.

When I first heard of sodium cables, I thought they would be used for some exotic super-duper extra-high-voltage cryogenic superconducting transmission system, but in fact the application was ordinary secondary-voltage underground residential distribution.

When I brought up the topic on another list, a former lineman said one of the problems was that when water got into the cable due to jacket damage, the conductor would corrode for a long distance from the point of entry. His crew ended up replacing a lot of the stuff.
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