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Birds Don't Like Wires Over 21 kV
3

Birds Don't Like Wires Over 21 kV

Birds Don't Like Wires Over 21 kV

(OP)
Here is a question that has bugged me for a long time but I never bothered to ask:

Does anyone know why birds do not perch on wires > 21 kV?

There are no 35 kV in this area so I don't know what they think of those.

I know I have never seen them perched on 60 kV or greater unless they are deenergized.

It must not kill them or else you would see dead birds for miles.

Do they not like electric field close to the wires?

Has this ever been studied?

RE: Birds Don't Like Wires Over 21 kV

My best educated guess would be:

1. Heat (higher loading on these circuits)

2. Higher electric field

3. Larger conductor size


Of course I could be very wrong since I know nothing about birds.

RE: Birds Don't Like Wires Over 21 kV

Whenever you are getting close to a naked wire (from a helicopter, for instance) there is a little (or quite nasty) spark before you establish a well conducting path with the wire.

Once on the wire, you do not feel anything. It's the spark that the birds don't like. I guess that they can sit on an de-energized wire and that they will continue sitting there when the wire gets energized again.

But they will not love the tickling when they leave the wire.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Birds Don't Like Wires Over 21 kV

In addition to the large spark seen in the video when attaching to or detaching from the wire, there is a steady state AC current flowing that charges and discharges the line worker each cycle. The worker is wearing a metal suit to equalize the electric field around their body so that the steady state current flows in the suit and not the worker's skin.

Although some wires do operate at uncomfortably high temperatures, many are also operated close to ambient. For many of our transmission lines, the lines will be warmer while de-energized on a still sunny day, than carrying typical power flows on a windy (> 2 m/s windspeed) cloudy day.

RE: Birds Don't Like Wires Over 21 kV

How many Ma is that spark?

Do you get a spark because the bird is one plate of a capacitor and the wire is another plate and when the two get close they discharge?

RE: Birds Don't Like Wires Over 21 kV

Yes, the capacitor analogy is correct. But there are three "plates" in the capacitor; the wire, the bird and the universe (or ground).

The arrangement is actually a capacitive voltage divider, like a capacitive PT, and current depends on equivalent capacitance, voltages involved and the Paschen's and other guy's laws. For a bird, it cannot be a lot of current. But nasty enough.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Birds Don't Like Wires Over 21 kV

Probably every bird has done it once though. We tend to think of them as stupid, but they are far from it. It's not likely 21kV though, behind my house we have some 25kV lines and above them, a set of 230kV lines. The 25kV lines are crowded with birds, especially during migration times, and are a favorite for hawks and eagles looking for rodents in the creek below. But the 230kV line are always clear. I once observed a young eagle go up from the 25kV line to get a higher perch and start to land on the 230kV, but immediately fly off, I think before he even touched it. They do perch on the cross arms though. So birds definitely use trial and error learning.

A pair of Turtle Doves has discovered, likely through trial and error, that the pine tree over my driveway is close enough to get some heat from the house, but dense enough to protect them from raptors. So they roost in the exact same spot every night and as you might imagine, my car ends up being their toilet. I tried a lot of things to discourage them from that roosting site, shiny balloons, mylar ribbons, a fake owl on the chimney, all with limited or no success. So for the past week I have been going out after dark, rain or shine, with my head lamp and a "wrist rocket" sling shot to fire a group of tiny pebbles into the tree where they are, just enough to disturb them. The first night they came back after an hour, the third night it was 3 or 4 hours, last night they finally did not come back. They learned...


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

RE: Birds Don't Like Wires Over 21 kV

I'm a structural guy and design T-Line poles and towers. Our EE's say the bird's feathers are affected by the corona around the HV lines. We don't have any HVDC and I wonder if the same thing happens there. When transmitting a lot of amps, the conductors get very hot. We run them as high as 300°C in an emergency and up to 250°C in normal operations which is hot enough to boil water. I suspect the high temps burn the bird's feet.

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

Wow! 250 degrees C! I gotta throw the BS flag on that one.
The rain does not boil off of transmission lines.
A line of any length at that temp would have losses greater than the load.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Birds Don't Like Wires Over 21 kV

Probably was Farenheit some time long ago. That would still be quite hot. But not impossible. What does 300 C do to elongation and tensile strength? Nothing good - that's for sure. BTW, never saw design rules allowing such high temperatures. Never, ever.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Birds Don't Like Wires Over 21 kV

2
You have to use high temp conductor to run it that high and I can assure you 250°C is the rating. You use ACSS (Aluminum Conductor Steel Supported) where the 270 ksi or 285 ksi steel core wire takes the tensile stress and the outer aluminum strands are totally annealed. On normal ACSR the aluminum is alloyed and takes the tension load. If you run ACSR too hot for too long, it will anneal the aluminum and you get run away creep and the aluminum fails then the steel core strands can't take the tension and it can fail.

Way back, they used to only run the ACSR 75°C normal rating and 90°C emergency. Later they used 90°C normal and 120°C emergency. They started to develop the high temperature wire to push more power down the lines. If the lines are lightly loaded, electrically, they are not too much above ambient and in the very cold weather, they will ice over and start galloping because of the shape of the ice. During the summer when everyone is running the air conditioner, the wire temperature goes up and the wire can sag an extra 20 feet from the unloaded position on an average 800 foot span.

Below is the output from a Sag-Tension program for a 795 MCM ACSR conductor on an 800 foot span in a 120 mph hurricane. When the wire is first strung, the sag is 13.50 feet at 60°F. After it creeps and gets loaded up, the sag goes to 25.36 feet at a max emergency operating temp of 120°C. The wire tension goes up to 12,907 pounds in a 120 mph wind from the initial stringing tension of 6501 pounds. The conductor has 26 aluminum strands over 7 steel core strands and is 1.108 inches diameter.

 WC  Weather Case Condition    Allowable     Actual  Allowable     Actual  Allowable     Actual       % of  OK  
  No. Description                    % of       % of    Tension    Tension   Catenary   Catenary  Allowable  or  
                                 Ultimate   Ultimate      (lbs)      (lbs)       (ft)       (ft)   Capacity  NG. 
-----------------------------------------------------------------------------------------------------------------
    6 60F          Initial RS        33.0       20.6                6501.2                5929.1       62.5  OK   
    6 60F          Creep RS          18.0       18.0                5667.1                5164.7       99.9  OK * 
   11 Hurricane    Initial RS        50.0       41.0               12909.3                3664.5       82.0  OK   
   12 NESC LIGHT   Initial RS        50.0       26.3                8272.8                5796.4       52.5  OK   


Ruling Span Sag Tension Report

 ---Weather Case--- | --Cable Load-- | -----R.S. Initial Cond.---- | ------R.S. Final Cond.----- |
                    |                |                             | --------After Creep-------- |
 # Description      | Hor. Vert Res. |  Max. Hori. Max        R.S. |  Max. Hori. Max        R.S. |
                    | -----Load----- | Tens. Tens. Ten     C   Sag | Tens. Tens. Ten     C   Sag |
                    | ---(lbs/ft)--- | (lbs) (lbs) %UL  (ft)  (ft) | (lbs) (lbs) %UL  (ft)  (ft) |
--------------------------------------------------------------------------------------------------
 1 15F                0.00 1.09 1.09    7690  7678  24  7018 11.40    6828  6814  22  6229 12.85  
 2 25F                0.00 1.09 1.09    7399  7386  23  6752 11.85    6533  6518  21  5958 13.43  
 3 30F                0.00 1.09 1.09    7265  7252  23  6629 12.07    6391  6376  20  5828 13.73  
 4 40F                0.00 1.09 1.09    6996  6982  22  6382 12.54    6131  6115  19  5590 14.32  
 5 50F                0.00 1.09 1.09    6741  6727  21  6149 13.02    5890  5874  19  5369 14.91  
 6 60F                0.00 1.09 1.09    6501  6486  21  5929 13.50    5667  5650  18  5165 15.50  
 7 70F                0.00 1.09 1.09    6277  6262  20  5724 13.98    5464  5446  17  4978 16.08  
 8 80F                0.00 1.09 1.09    6060  6044  19  5525 14.49    5275  5257  17  4805 16.66  
 9 90F                0.00 1.09 1.09    5859  5842  19  5340 14.99    5101  5082  16  4646 17.23  
10 100F               0.00 1.09 1.09    5671  5654  18  5169 15.49    4938  4919  16  4496 17.80  
11 Hurricane          3.33 1.09 3.50   12909 12833  41  3664 21.85   12907 12830  41  3664 21.86  
12 NESC LIGHT         0.83 1.09 1.42    8273  8253  26  5796 13.81    7579  7558  24  5308 15.08  
15 Rule 250 D         0.40 2.09 2.13   10580 10546  34  4945 16.19   10279 10243  33  4803 16.67  
16 75C(167)           0.00 1.09 1.09    4668  4648  15  4248 18.84    4114  4090  13  3739 21.42  
17 90C(194)           0.00 1.09 1.09    4368  4346  14  3973 20.15    3871  3846  12  3516 22.78  
20 120C(248)          0.00 1.09 1.09    3887  3863  12  3531 22.68    3483  3456  11  3159 25.36  
23 200C(392)          0.00 1.09 1.09    3081  3050  10  2788 28.75    3065  3034  10  2773 28.90  
24 250C(482)          0.00 1.09 1.09    2880  2846   9  2602 30.81    2868  2834   9  2591 30.94  
25 BLOWOUT 60         0.55 1.09 1.23    6938  6921  22  5644 14.18    6152  6132  20  5001 16.01  
26 FIRST CRACK CHK    0.55 1.09 1.23    6938  6921  22  5644 14.18    6152  6132  20  5001 16.01  
27 Max Temp           0.00 1.09 1.09    2880  2846   9  2602 30.81    2868  2834   9  2591 30.94  
28 Min Temp           0.00 1.09 1.09    8143  8131  26  7432 10.77    7323  7309  23  6681 11.98  
29 Rule 230B1         0.83 1.09 1.42    8273  8253  26  5796 13.81    7579  7558  24  5308 15.08  
 

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

Sounds like fault current temperatures. The conductors can recover if the exposure is brief. The Aluminum Conductor Handbook charts emergency loading temperature versus strength from 100 C to 150 C. Still hot enough to boil water and cook a bird.

RE: Birds Don't Like Wires Over 21 kV

Quote (stevenal)

4IK25GN-S5T6
That makes a lot of sense stevenal.
I have never seen it but has anyone else seen rain turning to steam or water vapor on transmission lines??

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Birds Don't Like Wires Over 21 kV

The rated ampacity of Drake 795 ACSR is 907 amps per wire and we run a 2 wire bundle at 138kV and 345kV. Some equipment in our substations is rated for 5000 amps. IIRC, the fault current is 63,000 amps for 138kV and 80,000 amps at 345kV but it should only last a few cycles before it trips a breaker.
http://www.southwire.com/ProductCatalog/proddetail...

500kV switch opening.
https://www.youtube.com/watch?v=PXiOQCRiSp0

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

Quote:

I have been called "A storehouse of worthless information" many times.

Uhhh, you might want to reconsider that. Simply no- in fact the opposite. :) :) For a structural guy this rivals what many long standing EEs post here- and they know their stuff. Great info!


As for not seeing steam- its a guess- but its possible that since water has a much higher thermal absorption capacity that it cools the conductor down significantly over 2ft/wind or still air temps.

RE: Birds Don't Like Wires Over 21 kV

Quote (Uhhh, you might want to reconsider that. Simply no- in fact the opposite. :) :) For a structural guy this rivals what many long standing EEs post here- and they know their stuff. Great info! )


Thanks for the kind words. I've picked up a little Electrical knowledge over the past 43 years of designing structures for Substations. The fault current gives me a Short Circuit Force on the buswork that I use to design the structure with other wind loads for extreme conditions. I know enough not to raise my hand too far inside a substation and to shuffle my feet if I hear any arcing (too much step potential between one foot and the other if you run).

AFA, the rain on hot conductor, I'm only guessing that it flashes to steam as the drops hit if it is indeed at or near max operating load. On foggy days you can hear the crackle around the wires which I assume are the tiny water drops flashing to steam. I'll have to ask the EE over the cubicle wall.

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

"I know enough not to raise my hand too far inside a substation and to shuffle my feet if I hear any arcing (too much step potential between one foot and the other if you run)."

If you are actually "running", only one foot will be in contact with the ground at any time. However, a good thing to keep in mind.

RE: Birds Don't Like Wires Over 21 kV

The crackling sound is corona discharges aka PD and has nothing with water vapour to do.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Birds Don't Like Wires Over 21 kV

Welcome and much earned :)

How many pounds of force does 80ka crank out? Around here we don't have to worry about that- yet lol.

RE: Birds Don't Like Wires Over 21 kV

Quote (If you are actually "running", only one foot will be in contact with the ground at any time. However, a good thing to keep in mind)


If you saw my bulk, you would realize it has been many years since I have "run" with only one foot on the ground at a time. :)

As far as the 80 kA, I'll have to dig out my spreadsheet and see what the figure is. You EE's know that it depends on the spacing of the bus. The equations in IEEE 605 are pretty conservative from what I have learned. I am the chair of the committee that is revising ASCE 113 and we are going over the first edition (I was Vice-Chair on that one) and adding some stuff.

AFA the crackling, I will defer to your expertise but it seems to happen in fog or very high humidity.

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

Quote:

AFA the crackling, I will defer to your expertise but it seems to happen in fog or very high humidity.

That's when the dirt and salts coating everything become more conductive and leakage currents begin worming their way thru it all. We get that here in our coastal town in-spades. While walking the dog, my wife and I have fun trying to see the actual arc-light given off by this process. We manage to see it whenever there isn't bright street lighting. Try it next time you hear it in the dark. It's across the insulators usually.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Birds Don't Like Wires Over 21 kV

Quote (That's when the dirt and salts coating everything become more conductive and leakage currents begin worming their way thru it all.)

I should have remembered that we had a long dry spell with little rain a few years ago in Galveston and we were having to wash insulators with deionized water at a huge expense.

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

Several kinds of wire including AAAC ACCR, GAP and ACSS can operate at 200C or higher.

Actual line temperature is often lower than rated line temperature since the ratings are for a near worst case weather day. If the wind is 4 ft/s instead of the typical assumption of 2 ft/s, the conductor temperature would be reduced from 200C down to around 150C.

If I have done the thermodynamics correctly, evaporative cooling from rain at 0.2 cm/hour falling on a 795 conductor would reduce the operating temperature by around 15C.

RE: Birds Don't Like Wires Over 21 kV

Hey there TxTowers, allow me to add my welcome to everyone else's.

As to the OP, I have seen birds sitting on the 28 kV lines in our province [Ontario, Canada] more often than I can recall, but they generally eschew anything 44 kV and above; the only exception is that ospreys seem to have no issues working around energized 44 kV equipment, often building nests one stick at a time into great sprawling affairs that render ganged manually switched devices completely inoperable [they must have an osprey nest-building construction code by which they choose only dry, high dielectric strength wood as a building material, as I have never heard of a feeder tripping off due this activity].

Since ospreys are a protected species, my utility's response has typically been to build a new non-electrical structure of slightly greater height in near geographic proximity and re-locate the entire nest onto the new structure in the off-breeding season while the birds are down south. Only very rarely have the returning ospreys scorned the new location and re-built their nest onto the same device.

I once recall seeing a very determined pigeon trying to alight on one phase of a 230 kV open-air bus; alas, every time it landed, it again flew back off, but stubbornly repeated the attempt a few feet further along the buswork . . . after fifteen minutes it finally gave up.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Birds Don't Like Wires Over 21 kV

I usually hang out here:
http://www.eng-tips.com/threadminder.cfm?pid=608

I try to answer technical questions about T-Lines and substations there, so if you need answers to structure questions, post over there.

As far as hi temp conductors, we have looked at 3M (don't remember the name) which IIRC, you basically rent from them, at least it was that way when they were trying to get to market for low sag conductor. And your Ospreys made their way south to my area of Texas so we built a structure near the nest and transferred it over.

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

Quote (How many pounds of force does 80ka crank out? .... )


I dug out my spreadsheet and ran a 50 GVa fault for a 345kV substation with 18'-0 phase spacing which I calculate will have a fault current of 83,600 amps. The load per foot of a 6" bus will be 42.4 pounds per foot for the SCF. In a 140 mph wind, the wind on the bus will be another 26.3 pounds per foot. When we combine SCF and 140 mph hurricane wind we take 80% of the short circuit current, so the combined wind and SCF force is 53.4 pounds per foot and a typical 30'-0 span would have 1.6 kips at the insulator on a bus support column.

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Birds Don't Like Wires Over 21 kV

At two 110 kV transmission line pillars that extend beyond our workshops during the preparations for the migration of crows in early morning and twilight , there are thousands of them.
Congratulations to the designer who, in addition to other parameters, and so many of these birds are predicted as a possible problem and the extra weight.

RE: Birds Don't Like Wires Over 21 kV

During bird migration season, I once saw hundreds of birds all land on a distribution line. When they got spooked by a passing car or truck, they flew off all in unison and caused the line to bounce up and down like you see with galloping transmission lines. I wouldn't have thought birds could cause that and maybe it doesn't happen often. I tried watching for it again and never could see them get the line bouncing around like I did the first time I saw it.

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