# What are these devices on this HV power line? **URL:** \ **Category:** Factual Questions\ **Created:** [October 7, 2014, 1:25pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646 "2014-10-07T13:25:39Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [October 7, 2014, 1:25pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/1 "2014-10-07T13:25:39Z")
[Photo](https://www.flickr.com/photos/11822576@N08/15468266662/). What are the devices attached to the bottom of the power lines (in pairs) for? ---
**Author:** ![yoyodyne](https://avatars.discourse-cdn.com/v4/letter/y/a9a28c/32.png) [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)\ **Post date:** [October 7, 2014, 1:28pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/2 "2014-10-07T13:28:33Z")
> **[Stockbridge damper](https://en.wikipedia.org/wiki/Stockbridge_damper)** > > A Stockbridge damper is a tuned mass damper used to suppress wind-induced vibrations on slender structures such as overhead power lines, long cantilevered signs and cable-stayed bridges. The dumbbell-shaped device consists of two masses at the ends of a short length of cable or flexible rod, which is clamped at its middle to the main cable. The damper is designed to dissipate the energy of oscillations in the main cable to an acceptable level. > Wind can generate three major modes of oscillation i... ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [October 7, 2014, 1:32pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/3 "2014-10-07T13:32:29Z")
Thanks. I thought it might be something like that but they are kind of small, and in this case, the line is very short, so I didn’t think it would need damping. I guess they do it as a matter of course. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [October 7, 2014, 1:58pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/4 "2014-10-07T13:58:11Z")
Around here, there are power line braces that are (I would guess) fiberglass or ABS and hold four lines about 18 inches away from each other. They’re placed about every 20 feet on roadside runs and I assume their purpose is to keep wind and small branches from pushing the lines together. They look just like birds being electrocuted. Some industrial designer had a sense of sick humor. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 7, 2014, 4:31pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/5 "2014-10-07T16:31:46Z")
> [@Amateur\_Barbarian](#): > > Around here, there are power line braces that are (I would guess) fiberglass or ABS and hold four lines about 18 inches away from each other. They’re placed about every 20 feet on roadside runs and I assume their purpose is to keep wind and small branches from pushing the lines together. > > They look just like birds being electrocuted. Some industrial designer had a sense of sick humor. No, those are [bundled conductors](https://en.wikipedia.org/wiki/Overhead_power_line#Bundled_conductors). All four conductors are in phase. Think of it as one multi-strand wire. ETA: Oh, and scroll up a little to see what one “wire” looks like. Fascinatingly complex. ---
**Author:** ![andrewm](https://avatars.discourse-cdn.com/v4/letter/a/c57346/32.png) [@andrewm](https://boards.straightdope.com/u/andrewm)\ **Post date:** [October 7, 2014, 4:35pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/6 "2014-10-07T16:35:45Z")
> [@beowulff](#): > > Thanks. > I thought it might be something like that but they are kind of small, and in this case, the line is very short, so I didn’t think it would need damping. I guess they do it as a matter of course. The Wikipedia article says that the vibrations damped by the device are only on the order of the cable diameter. A line doesn’t have to be very long to allow such a small amount of flex, but even small movements repeated enough times can eventually cause enough damage to break the connection. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [October 7, 2014, 5:18pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/7 "2014-10-07T17:18:20Z")
> [@ZenBeam](#): > > No, those are [bundled conductors](https://en.wikipedia.org/wiki/Overhead_power_line#Bundled_conductors). All four conductors are in phase. Think of it as one multi-strand wire. I’m not sure that’s the case - I’ve seen multi-strand conductors on big towers and understand the practice. These are on roadside poles and are the only power conductors - the rest are low-voltage runs several feet lower and obviously cable, fiber, phone etc. I can’t find a photo online; I’ll stop and snap a few pix next time I pass one of the photogenic locations. > [@](#): > > ETA: Oh, and scroll up a little to see what one “wire” looks like. Fascinatingly complex. Power technology is so damned cool in the details. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [October 7, 2014, 5:50pm UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/8 "2014-10-07T17:50:14Z")
you also might see three phase power cables over a long span have spacers. a long span where a tower can’t be place like a divided highway or river. the cables have enough because of the sag to touch if moved nonuniformly. ---
**Author:** ![bizerta](https://avatars.discourse-cdn.com/v4/letter/b/3be4f8/32.png) [@bizerta](https://boards.straightdope.com/u/bizerta)\ **Post date:** [October 8, 2014, 1:22am UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/9 "2014-10-08T01:22:05Z")
Since the vibration damping gizmos have been identified, can anyone identify the triangle thingy on the left side of these telephone poles. I observed these on a drive from El Paso to Carlsbad last May. [www.bizer.com/000nm.jpg](http://www.bizer.com/000nm.jpg) ---
**Author:** ![yoyodyne](https://avatars.discourse-cdn.com/v4/letter/y/a9a28c/32.png) [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)\ **Post date:** [October 8, 2014, 11:56am UTC](https://boards.straightdope.com/t/what-are-these-devices-on-this-hv-power-line/700646/10 "2014-10-08T11:56:54Z")
> [@bizerta](#): > > Since the vibration damping gizmos have been identified, can anyone identify the triangle thingy on the left side of these telephone poles. I observed these on a drive from El Paso to Carlsbad last May. > [www.bizer.com/000nm.jpg](http://www.bizer.com/000nm.jpg) [Bird excluder](https://www.vogelabwehr.de/en/shop/articles/C/C-05.php)