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View Full Version : OT: How strong is a power line? (Tree down in todat's storm)



PStechPaul
07-18-2017, 07:05 PM
About 3:00 this afternoon a fairly powerful thunderstorm rolled through. There were some pretty close lightning strikes followed quickly with thunder. Tibbs was not happy. Then the lights flickered several times, while I heard the "bong" sound of current in the power lines, and the power went out completely. When I looked out the window, I saw that a moderate-size tree had fallen next to the house, and it looked like it had landed on top of my car. I assumed it had taken out the power lines, so I called BGE and they said they would be out soon.


The rain let up a bit and I was able to go outside, where I saw that the tree had been caught by the power lines and my cherry tree, and it had not struck the car. The crown of the tree was hanging over Warren Road and looked to be dangerous, so I called 911 on my cell phone. My land line phone was out. I got into my car and drove further up into the yard to clear the tree.


BGE and the police arrived about 4:00 PM while Tibbs and I were sitting outside. They pretty quickly cut up the tree with a pole saw, and soon restored power. Here are pictures and some video clips:

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3454.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3458.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3459.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3461.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3456.AVI (17M)

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3457.AVI (17M)

Jim Stewart
07-18-2017, 08:11 PM
Paul, run - don't walk - to your nearest 7-11 and buy a lottery ticket!

That was your power drop. It's usually two aluminum insulated wires wrapped around a steel stranded carrier/ground wire. It's probably 3/8 to 1/2 inch diameter, depending on the current capability of your drop (usually 100-200 amps).
As you saw, it was strong enough. A few years back in a storm a tree brought my power drop down, but in my case it ripped the mast off the side of my house. Bent it to nearly 90 degrees. That mast was sch. 80 2" galvanized steel.

-js

J Tiers
07-18-2017, 08:19 PM
The answer to how strong..... is usually "A lot stronger than the tie point on your house".

Standard procedure is for the line to pull the attachment off your house, and maybe yank out your service entrance cable. Then you call the powerco, and they tell you they are not coming, and in fact will not turn your power on until you have an electrician fix the service entrance cable (to the tune of a few hundred bucks, depending on what got shredded.)

Your attachment is a goodie.

BCRider
07-18-2017, 08:20 PM
I hadn't realized that the drop wire also had a steel cable messenger for the ground. I'd assumed it was simply more of the commonly used aluminium cable.

I'm also surprised in that case that the tension of the tree didn't rip your drop right off from or right out through the wall of the house. That must have been a helluva load on it as it settled into place. In fact you may want to look in the basement and see if you're still sitting on the right spot of the foundations :D

Jim Stewart
07-18-2017, 08:24 PM
The problem with all-aluminum wires is they sag. And sag some more. And more. All from just the weight of the wire.

My drop did rip the attachment from my eaves, bending the mast where it screwed into the meter case. I suspect a heavier tree would have ripped the meter and the service panel off my house too.

-js

J Tiers
07-18-2017, 08:30 PM
I hadn't realized that the drop wire also had a steel cable messenger for the ground. I'd assumed it was simply more of the commonly used aluminium cable.
....

A good deal of cable is "ACSR" as described above.... Aluminum Conductor Steel Reinforced. Basically any bare conductor cable is for overhead, and will be ACSR,

Arcane
07-18-2017, 08:44 PM
As an old Journeyman Lineman I'm very surprised your mast held up; that's a pretty skoocum tree.

Overhead house services tend to be Triplex cable with an ACSR (aluminium conductor steel-reinforced) neutral and for a 200 A entrance usually 1/0 aluminium conductors. From http://www.prioritywire.com/specs/Triplex%20Service%20Drop.pdf the breaking strength of 1/0 triplex is rated at 4380 lbs. Some triplex with 1/0 conductors had a reduced sized neutral (usually #2 neutral with 1/0 conductor) with a breaking strength of 2850 lbs.

lugnut
07-18-2017, 08:50 PM
Depending on if the line is a primary or secondary. Primary line usually have a steel core with seven aluminum wires wound around the steel wire. Secondary wires are or could be two covered aluminum wires with one bare wire. The primary lines are pretty tough, and made to withstand a lot of force. Secondary lines are usually designed to pull the connecting attachments from the building. Because nothing ever happens like it should, treat all power lines like they are there to KILL you and leave the area.

boslab
07-19-2017, 12:27 AM
Well the only conclusion I come to as to its strength is just strong enough, that's good!
We used to have twisted copper over here, worked fine but is being replaced with Ali at the taxpayers expense, when I asked what was happening to the copper they didn't want to answer, it's being sold as scrap and the utility companies seem to be pocketing the money, plus the taxpayer is also footing the 11 billion it's costing to install smart meters, and they add the cost to your bill, I see a pattern developing!, if I tried double scamming the consumer and the treasury I think I'd be in jail, many rules has the law.
Getting back to cable, ours is coaxial these days, Ali and steel, I've seen a tree leaning on a wire, fir or pine, must have been 50' so I'm guessing that stuff is fairly strong, the guy from the utility said they were installing carbon fibre reinforced as well, cheaper, never heard of the stuff before myself.
Mark

754
07-19-2017, 02:27 AM
I think the fallen tree is being held up a lot by the other tree.
So if you cut between the ground and the wire, unless supported, the load may increase if you cut it unsupported.

PStechPaul
07-19-2017, 03:29 AM
I think you are right. The cherry tree took a good bit of the force. Here are a few more pictures:

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3462.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3463.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3464.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3465.jpg

I was surprised how quickly and easily the work crew cleared this up, with a gas-powered pole saw. I thought they would need a bucket truck and perhaps a prop to support the tree near the wire. But first they cut the small limbs from the crown of the tree that were hanging over the road and caught in the cherry tree, then they cut the tree near the line, which took much of the weight off it. Then they cut it closer to the trunk, and it was on the ground. A few minutes more and they had the driveway clear. I have a bit of work to do, but they did a really good job. This is a locust tree, and it looks like it was still fairly healthy. I think it was just a strong gust of wind and soft ground where it didn't have very deep roots. I had been planning to take it down - now it's done - and it will provide some good firewood once it's cut up and seasoned. The cherry tree is not very healthy, and needs to be severely trimmed or possibly taken down. But I'm glad it was still there to save my car!

PStechPaul
07-30-2017, 01:17 AM
Early Saturday morning, about 6 AM, I was in bed half asleep, and I heard a crash-thud sound. I first thought it might be another accident on the road, but when I took a good look, I saw this:

http://enginuitysystems.com/pix/house/Branch_3476.jpg

Yes, same place where the tree came down, but this was just a branch from another tree. No apparent damage, but it was blocking half of Warren Road.

http://enginuitysystems.com/pix/house/Branch_3477.jpg

http://enginuitysystems.com/pix/house/Branch_3478.jpg

Upon closer look, it appears to be either locust or walnut, tangled up with grape vines and other weeds. It had rained rather heavily overnight and the weight of the wet leaves and vines probably pulled the whole mess down.

http://enginuitysystems.com/pix/house/Branch_3479.jpg

I probably could have handled the mess myself, but the main branch seemed pretty heavy, and I have had back problems. My gas chain saw has been sitting a long time and probably will need some work to get running. I have an electric saw and extension cord that should reach, and I have some heavy-duty loppers that can cut up to 1-1/2" branches. So I called 911 and started trimming off some of the smaller pieces. A policeman arrived and he was able to use the lopper to cut it down enough to pull it off the road and clear enough for me to get my car out. I wonder what will be the next bit of excitement here?

lakeside53
07-30-2017, 10:30 AM
you can call 911 for that? Probably get a citation around here :)

J Tiers
07-30-2017, 11:29 AM
Blocked roads are usually legitimate for a call, depending on the road. But in most cases, folks here would just haul it over to the side. If it is a whole tree, that might be different.

Concerning power line.... Neighbor had a biggish branch on her drop, clearly straining it. Branch maybe 6 inch size, down and leaning on the wires. Powerco gave a date 3 weeks later that they would deal with it.

Since she had the 3 wire spiral drop, but everything was still soaked from the rain I just put on the usual rubber gloves and leather ones over them (in case of pinholes or abrasions of the insulation), and we cleared it off with a come-along and saw. Safe enough, the gloves are good to 3kV at least.

Dan_the_Chemist
07-30-2017, 11:48 AM
Call 911 for any situation that may involve an immediate danger to life. Trees across roads, partially blocking roads, and trees on power lines all qualify. Just a week ago we had a tree only partially blocking a country back road and a rather speedy driver hit the tree, flipped at least 1 1/2 times, and came to rest on the side of the car. Amazingly the driver was relatively unscathed as the car had something like a dozen airbags, all of which inflated...

Trees on power lines are a danger to life because too many people assume that the line is dead. They go to cut the tree up and wind up dead. Our fire department makes sure there is no immediate threat to civilian health and safety, and then we call the power company and wait for them to come chop up the tree. They can pull the gates on the appropriate poles to isolate that section of power line before cutting it. In large regional disasters we will sometimes cut the trees up after the power company has pulled the gates, but we will not do so before then.

brian Rupnow
07-30-2017, 12:16 PM
About 30 years ago, I had a cottage up in the Muskoka lakes region about 2 hours north of Toronto. On one side of the driveway, there was a huge old birch tree, which had been dead forever, all the branches were gone off it, but the main body of the trunk was easily 40 foot tall. I was afraid it might come down on the cottage in a heavy wind, so I fired up my trusty old chainsaw and cut it down.--And down it came, right across the hydro wires that lead from the main poles out at the road to the mast on my cottage!!--My mast held up all right, but it ripped the wires right out of the transformer on the pole. This was about 2 weeks after Christmas, and when I called Ontario Hydro and told them what I had done, they sent in a huge 4 wheel drive monster of a truck and two crewmen to repair it. Of course I was feeling like a world class idiot by this time, and when one of the crewmen asked me if I had "Just got that chainsaw for Christmas?" all I could do was shuffle my feet and say "Duh--Yeah".

dave_r
07-30-2017, 01:11 PM
you can call 911 for that? Probably get a citation around here :)

Or you hit the jackpot and you get shot by the responding officers...

reggie_obe
07-30-2017, 01:32 PM
I wonder what will be the next bit of excitement here?

Who know? Should you wait and find out?
Maybe you should have a tree service come out and trim all the branches overhanging your house, driveway and service drops.

Spandau
07-30-2017, 02:46 PM
My brother has a pole with transformer that is literally being supported by the power lines. A drunk crashed into, not the pole, but into the guy wire holding the pole, ripping out the 4 ft. long embedded tie out of the ground. The base of the pole was displaced by about 2 feet, and the pole shattered. The electric company has known about it for weeks, and haven't done anything. It will require multiple trucks, and flaggers on both ends due to it being on a blind curve with hills on both ends.

You can actually see the pole moving with the wind, and the air from passing semi's (55 MPH state highway).

Funny enough, Frontier, who supplies his internet and phone, was there 2 days after the accident to restore service. The tech said he had to move the connection point over 4 feet because the pole is so out of whack.

TGTool
07-30-2017, 03:58 PM
I had an interesting situation develop trying to fix a tree problem. A tree in the side yard had grown to the point that a moderate sized branch (wrist size) was extending over the line to the house and threatening to drag it down. It seemed like a good idea to trim it before it became a problem.

So I'd brought the extension ladder over, and at its fullest extent it was just long enough to reach over the branch. I climbed up carefully with a rope and tied the ladder so no jacking around when I got to sawing would cause a problem. So the sawing off of the offending branch went off uneventfully. Undercut a little, then cut down just further out so it wouldn't just tear and be left hanging.

All well and good. Now untie the ladder and take everything down. As I started to untie the rope, I realized there was just one thing I hadn't counted on. The stub of the limb was now noticeably lighter and at its new relaxed position the ladder would not be long enough to reach. In other words, as soon as I loosened the rope, the ladder was going to slip under the limb and I was headed for a faceplant on the top of the ladder. I did a quick mental calculation of how fast I could shinny down relative to the acceleration of gravity and the odds didn't look in my favor. So, there I was. I couldn't untie the ladder at the top but I wasn't keen on a hanging ladder yard decoration in perpetuity. Yeah, the home shop solution would be just buy another tool. Get a longer ladder to use to rescue the one I already had.

I finally resorted to hanging an arm over the limb, maintaining enough weight to keep the ladder in place while I untied the rope. Then I retied it with a bight on the loose end that I could tug once I got to the ground. I may even have been thoughtful enough to have an end over the branch so I could use it to lower the ladder once untied, I don't remember. Fortunately it ended well, but there was a long "Oh Sh1t" moment of realization up at the end of the ladder.

PStechPaul
07-30-2017, 09:55 PM
Today I used the electric string trimmer to cut the high grass and weeds in the front yard and down the driveway to the remains of the branch that had come down. I used my bypass loppers to cut the smaller limbs and piled up the pieces that will make good kindling once seasoned (perhaps by end of year). I also pulled the remainder of the downed tree out of the cherry tree, and now it will be just a quick and simple chain saw job to get everything clear and organized.

http://enginuitysystems.com/pix/house/Branch_3485.jpg

http://enginuitysystems.com/pix/house/Branch_3486.jpg

A closer look at the tree that fell over because the roots had not enough to hold onto:

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3482.jpg

http://enginuitysystems.com/pix/house/Storm_Tree_Down_3484.jpg

I was unsure about calling 911, but I wasn't sure I could safely take care of the situation myself. It was nice of the cop to clear the debris enough to allow me to get out of the driveway. I was also somewhat concerned that I had my dog Mr Tibbs tethered outside in the yard and he was barking, but not posing a threat. However there have been a lot of incidents where cops have shot and killed dogs that were tied up or just displaying friendly curiosity.