Why hang this on high voltage power lines? (ANSWERED) - Page 1
Forum section: electronics / projects

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 07:00:54 pm
content: Last Sunday I came across some high voltage power lines that had something hanging on the lower lines.The things are justvisibleon Google Maps, and are only found on a couple of sections. I have been visiting that region for years and they must have been on those lines for at least that long, so it doesn't seem to be a temporary thing...Does anyone have any idea what they're for?

author: electr_peter
author_rank: Unknown
timestamp: August 09, 2016, 07:14:27 pm
content: Maybe this round object smoothes out electric field and reduces corona discharge losses?

author: Ice-Tea
author_rank: Super Contributor
timestamp: August 09, 2016, 07:18:22 pm
content: To increase radarreflection?

author: rx8pilot
author_rank: Super Contributor
timestamp: August 09, 2016, 07:25:09 pm
content: Maybe a non contact 'test point' that radiates a field that can be measured for voltage and current. Much safer than a multimeter

author: Tomorokoshi
author_rank: Super Contributor
timestamp: August 09, 2016, 07:27:11 pm
content: Mind control.

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 07:29:00 pm
content: Quote from: Ice-Tea on August 09, 2016, 07:18:22 pmWho knows... A bit to the north-east from where I took the photos, I foundthisairstrip on German soil that was apparently once anRAF base.But the power lines don't seem to be anywhere near the airfield. Edit: ...and they're on the lowest lines, not on the top lines...

author: LazyJack
author_rank: Frequent Contributor
timestamp: August 09, 2016, 07:32:03 pm
content: Is this over a road or a river? Then radar reflector for aircraft following the road or ship going on the river (if they carry something high).

author: C
author_rank: Super Contributor
timestamp: August 09, 2016, 07:32:26 pm
content: When you add a weight to a cable like this you change the frequency that an oscillation can happen.Cable with no weight = one frequencyCable with one weight = three frequencies all with damping.Cable with two weights = Six frequencies all with damping if I count correct.

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2016, 07:38:21 pm
content: Yes, I would say mechanical damper too.

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 07:39:44 pm
content: Quote from: LazyJack on August 09, 2016, 07:32:03 pmNo, it's over farmland.

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 07:41:59 pm
content: Quote from: C on August 09, 2016, 07:32:26 pmI considered this, but if you're just going to put weight on the lines, why then in that elaborate (and seemingly lightweight) shape? Also, why only on one of the lower set of lines? And why only on a few stretches of power line?

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2016, 07:47:41 pm
content: Hmm, from the that angle theydolook a bit more like radar reflectors, but if so, why not on the upper conductors?

author: Jeroen3
author_rank: Super Contributor
timestamp: August 09, 2016, 07:47:48 pm
content: They are a bit large for dampers.Ask here:http://www.hoogspanningsnet.com

author: C
author_rank: Super Contributor
timestamp: August 09, 2016, 08:04:39 pm
content: Why lower and not higher cables?Simple, The wind is different.Why not on all?Why spend money where it is not needed.Why the rounded shape?This is very high voltage and any sharp point is a possible corona discharge point.The long shape helps spread out the damping.

author: StillTrying
author_rank: Super Contributor
timestamp: August 09, 2016, 08:45:35 pm
content: Seats to sit on while you're admiring the view.They probably found them 2 cables twisted together once after high winds, so added the seats to prevent it happening again.

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 08:50:44 pm
content: Quote from: Jeroen3 on August 09, 2016, 07:47:48 pmThanks for the link. Apparently my question here was atopicon that forum too in 2012, but without a definitive answer.There was a remark about the odd way the isolators for the conductors with the "things" were placed. My photos also show the conductors hanging on vertically placed isolators while the conductor with the things hanging on them have V-shaped isolators... I had noticed this before but i forgot and it went unnoticed this time.Looking at the Google Maps link in my fist post, I notice that the stretches of power lines with the things on it are in South-west to North-eastern direction. SW winds are prevailing over here (and a "Southwestern" is the name for a storm over here), but I don't know of that ever having been a problem as this far inland, wind speeds are usually not that high (although nearby, in Germany, I could see several wind turbines).

author: Jeroen3
author_rank: Super Contributor
timestamp: August 09, 2016, 08:59:39 pm
content: Quote from:http://www.tdee.ulg.ac.be/doc-30.htmlSame shape?

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 09:04:15 pm
content: Thanks. Wind damping seems to be the answer indeed.Googling "Den Hartog wind damper" I stumbled uponthisarticle on galloping power lines showing the exact same design as I found near Vlodrop.It's an aerodynamic drag damper. It probably explains my observation why they're only on the part that's facing SW to NE. No doubt there were galloping problems after the line was taken into service, and they countered the problem with the altered arrangement of the isolators and the addition of the aerodynamic drag dampers.Thanks for pointing me in the right direction.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 09, 2016, 09:14:44 pm
content: To prevent this, right?

author: IanB
author_rank: Super Contributor
timestamp: August 09, 2016, 09:20:41 pm
content: Interpreting what was quoted above, and the pictures, the specifics appear to be as follows:Under certain conditions, ice formation on the cable can lead to undesirable up-and-down motions ("galloping") when the wind blows across the wire. The damper hung from the wire causes the cable to twist when the wind hits it, which shifts the ice profile away from the critical angle that would lead to the bad vibrations.However, placing such an item on the cable would also cause the whole cable to be blown sideways, which is not wanted. To resist this tendency the vertical insulators are replaced with the "V" shape suspension which can resist the sideways movement that would otherwise occur. Thus the cable can twist, but not swing.

author: IanB
author_rank: Super Contributor
timestamp: August 09, 2016, 09:21:59 pm
content: Quote from: Jeroen3 on August 09, 2016, 09:14:44 pmYikes!

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 09:22:03 pm
content: Indeed.Googling for this I had already found"Stockbridge dampers"that seem to have the same function as the aerodynamic drag damper.

author: jitter
author_rank: Frequent Contributor
timestamp: August 09, 2016, 09:25:06 pm
content: Quote from: IanB on August 09, 2016, 09:20:41 pmThat would be an interpretation I can live with. But why only on that particular conductor and not on the others?Edit: I looked at the Dutch forum again that Jeroen3 linked to and it seems that the stretch near Vlodrop is (or was) a bit of a testing ground for configurations. Perhaps the dampers were only part of a test and not a solution to a real problem.

author: C
author_rank: Super Contributor
timestamp: August 09, 2016, 10:34:47 pm
content: why would there have to be a simple answer other thento keep the stress below the stretch or break point of cable and to keep one wire from getting a specified distance from another.A gusty wind coming up a hill could easily have more effect on a lower wire then higher. One area of the wire vs the whole span of wire.Those devices can have many functions at same time.Think of lifting an area of the span on a wind gust and then dropping it when the dust stops. A big drop and wire breaks.Weight, wind weight, wind sail, wind drag to just name a few of what the device could be doing.The net result is with two devices on the line you have changed things from ONE problem to SIX smaller problems. Where one is too much and six is ok.

author: jitter
author_rank: Frequent Contributor
timestamp: August 10, 2016, 05:54:40 am
content: Maybe you're right and that was the simple reason and solution. But I can't ignore the remarks made on the Dutch forum that some parts of the grid are (or were) used for testing different configurations, and this bit of the power lines happens to be one of them. Apparently, the design of the towers also seems to deviate from what is normally used over here.It's no use asking the power companies. When the grid wasn't privatized technicians took good care of it and went the extra mile to keep it running smoothly. Now the private companies only do the bare minimum that the contracts say, they're probably ignorant of what went on in the past.

author: chris_leyson
author_rank: Super Contributor
timestamp: August 10, 2016, 06:54:50 am
content: I was going to say Stockbridge dampers do the same job but Jitter beat me to it.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2016, 12:19:25 am
content: I have only seen or maybe notice the triangular wing type before.Instead of radar reflectors, I have seen what look like large colored beach balls attached to the lines making it easier for aircraft to see them.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: August 11, 2016, 03:21:08 am
content: This may be a test area, but another possibility exists. Unless the towers are infinitely stiff () the lines are coupled, so damping one line has an effect on the others. One may be all that was necessary. The triangular slotted dampers are quite common on telephone and distribution wires in the US. Numbers vary widely, from none to as many as half a dozen on a single wire segment. Presumeably these are fitted on an as needed basis with no analysis beyond looking at the wires or checking failure records for a line. The variations in number would reflect a combination of variations in local conditions and attitudes of the field guys installing them.The aerodynamic dampers seem to have completely taken over from another older technology that is still seen hanging from wires, a weighted spring/oil dashpot.