dennisg@felix.UUCP (Dennis Griesser) (09/19/87)
In response to mercury-filled speaker cables, Larry Lippman <1997@kitty.UUCP> warned about the toxic hazard presented by mercury. Then he said... > Now, for a more practicable idea, consider the use of SODIUM-filled >cables, which have been available to the electric power industry for a number >of years. Sizes go up to at least 500,000 circular mils, and I know for a >fact that the cable is available with an insulation rating of 15 kV for >direct-burial applications. Sodium-filled cable really does exist. Many years ago, my father worked in Union Carbide's NaCon division where they were being developed. What Larry failed to mention, and should have since he was reminding us about the dangers of mercury, is that sodium reacts vigorously with water. The insulation needs to be quite water-tight, and terminating the ends must be interesting. > Be the first on your block to have sodium-filled speaker cables! >They'll beat ol' Monster Cable any day... I don't think so. If I recall properly, the big motivation for sodium cable is that sodium is a lot more plentiful than copper.
larry@kitty.UUCP (Larry Lippman) (09/21/87)
In article <7578@felix.UUCP>, dennisg@felix.UUCP (Dennis Griesser) writes: > In response to mercury-filled speaker cables, Larry Lippman <1997@kitty.UUCP> > warned about the toxic hazard presented by mercury. Then he said... > > > Now, for a more practicable idea, consider the use of SODIUM-filled > >cables, which have been available to the electric power industry for a number > >of years. Sizes go up to at least 500,000 circular mils, and I know for a > >fact that the cable is available with an insulation rating of 15 kV for > >direct-burial applications. > > Sodium-filled cable really does exist. Many years ago, my father worked in > Union Carbide's NaCon division where they were being developed. > > What Larry failed to mention, and should have since he was reminding us about > the dangers of mercury, is that sodium reacts vigorously with water. The > insulation needs to be quite water-tight, and terminating the ends must be > interesting. I was being facetious, so I didn't mention it! Sodium has approximately 40 percent of the conductivity of copper, so it's not that bad a conductor. Sodium has about 1/3 the density of aluminum and about 1/10 the density of copper. Sodium-filled cable is extremely lightweight when compared to that of copper or even aluminum. Sodium is a byproduct of chlorine production, is quite plentiful, and costs less per pound than aluminum. The use of sodium for underground high-voltage cables (4,160 volts and above) awaited the development of a practicable cable manufacturing process, and of a practicable and safe connection method. Sodium-filled cables for underground high-voltage distribution have been used for at least 20 years. The cable terminations have a "corkscrew" which digs into the sodium filling inside the cable; this termination has a plastic sheath which fits over the end of the cable and seals it with a cement. A conventional terminal lug protrudes from the cable termination for connection to distribution apparatus. Besides being of low cost and light weight, sodium-filled cables have the advantages of fault limitation and easy fault localization. Unlike conventional cables which might have a fault (say, an insulation defect or injury) with slowly increasing leakage to ground, the slightest leakage in a sodium-filled cable causes rapid destruction of only a small portion of the cable. Following such a fault, the formation of sodium hydroxide at the exposed ends of the cable seals the remainder of the cable from moisture penetration beyond a few feet. Speaking as both an EE and chemist, I feel that sodium-filled cable is an effective means of providing low-cost underground electric power transmission for voltages between 4.16 and 34.5 kV. However, sodium-filled cable has been severely under-utilized. I don't know why this is, other than there appears to be some unfounded apprehension about its use. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"