Oval conductors resist vibration and galloping. Now specifiers can get sizes down to AWG 6.
- Published in Southwire's T&D Update newsletter in March 1998
- Reprint permission granted
Ice and wind are very democratic. They bring down small overhead lines and large ones without discriminating. Now smaller overhead lines can have the galloping and vibration protection their bigger brothers have had for some time: oval cross-section conductors.
"Oval conductors as small as AWG 6 - in both ACSR (aluminum conductor steel reinforced), and AAC (all aluminum conductor) constructions-are now available from Southwire," says Gene Sanders, senior development engineer. "That opens a new range of applications for oval conductors."
Oval conductors break up the continuous round cross sectional profile that helps make conventional conductors the victim of aeolian vibration and ice galloping. The spiraling oval cross-section delivers all the gallop and vibration resistance of twisted-pair conductors-or better-without the cost premiums or installation problems twisted pair impose.
Many smaller lines get protection
"Failure of a major overhead line is dramatic," says Sanders, "but utilities and transmission companies also have many miles of smaller overhead transmission and distribution lines to worry about. Where ice galloping is common, those smaller lines can be a bigger total headache than the large ones."
The smaller sizes of oval conductors extend vibration and galloping protection to circuits that haven't had it before. The smallest commonly available twisted-pair conductor uses two AWG 6 conductors. Cable buyers can choose oval conductors from AWG 6 to 1272 kcmil, including the common AWG 4/0 and 266.8 kcmil sizes.
In the Midwestern U.S., where ice galloping is seen often, overhead users are trying out the smaller size oval conductors. An Iowa/South Dakota utility company has been using vibration-resistant conductors for all new overhead construction since 1989. They're putting in a 69kV transmission line using 795 ACSR oval for the three phase conductors and also for the static line. Users in Nebraska, South Dakota and Kansas are putting up 4/0 oval conductor distribution lines.
Ovals reduce installed costs
Oval conductors save money over twisted-pair construction in several ways. To begin with, oval conductors can use standard round-conductor fittings. Several hardware manufacturers have approved their standard round splices, dead-ends and other fittings for use with oval conductors. Please note that the standard fittings must be selected specifically for use with each oval conductor construction.
Oval conductors save money on installation, too. There's none of the time consuming tensioning and handling hassle that's common with twisted-pair constructions. Splicing and terminating are just like round wire.
Engineers planning an oval ACSR installation can use standard ACSR guying and sagging standards. No special engineering is needed. That can shorten project schedules and save scarce engineering resources.
"We're excited about the availability of oval conductors in the smaller sizes," says Sanders. "They can help deliver gallop and vibration resistance to a lot of miles of overhead wire."
