Oh my frikken God. I have pulled sparks like that off of a Van de Graaff generator and a Wimshurst machine, never would I imagine doing it with something that can also supply thousands of amps.
The first video, the sparks didn't quite seem real, the video may have been chopping them but the frequency didn't even sound quite right.
The second video was much more convincing, but I'm not sure why they were working on this LIVE somewhere in the middle of the line.
Loopy Byteloose, there was also a spark at the very beginning as the helicopter approached.
I know two people (Lineman) that have lost arms and or legs because they became a human fuse. If the first video is is truly part of the training, then I pray for the families, but in the same breath. With something that serious, you don't cut-up and laugh about it. "Playing" with that kind of power is just asking for trouble - be careful what you ask for.
They used a probe to bring the helicopter up to the line voltage,
That cannot be right. Unlike my playing with a Van de Graaff generators and such where you can stand on a plastic bucket and charge yourself up to the voltage on the dome, those lines are carrying AC. That means they are at a billion volts one millisecond an minus a billion volts 10ms later.
So what voltage does that helicopter reach when it leaves?
And perhaps there is the answer. If the line were DC and the copter was "up to the line voltage" then there would be no spark as it left. Charge will not want to move from place to place at the same voltage.
BUT, as it is AC then as the copter moves away at some point it is charged to, say, plus a billion volts. But then the line is driven down to minus a billion volts. Tick, there is the spark.
Note: In this post "billion" is whatever huge peak voltage that line reaches.
There are several voltage stages depending on where you are between your house and the sub-station. I don't know off hand, but my lineman friend said something like the wooden poles are 2700V at 5Amps ... the metal Poles are much higher voltage.
The Helicopter by itself generates an electrostatic charge from the rotating blades that is DC ,,, that is what you are seeing, not the HV from the power line... (I think)
If a helicopter "generates an electrostatic charge from the rotating blades that is DC" then we would be used to seeing such a spark show everytime a helicopter landed. We do not.
The job of the Static man is to use a grounding rod to attach to the hook so that the static electricity conducted by the helicopter is grounded out and does not end up killing a Marine.
Heater, they most certainly do have a VERY significant charge. I worked in aeromedical healthcare for a long time and there were numerous times where the bird pulled an impressive arc just before landing. You definitely do not want to touch a helicopter in hover/no ground contact. I think the military guys use a grounding pole or something similar. I'm not exactly sure how they rappel onto a surface without getting the Smile knocked out of them. Anybody know?
Interesting. So how come all helicopters landing anywhere don't have a "static man"? I have watched the air ambulance landing outside our local hostipital many times, no sparks.
Well, OK, normally when a copter lands there is nobody standing under it ready to get zapped. On the other hand we don't seem to see sparks as in the video jumping between copter and ground.
Now I wish my old car had a "static man". I used to get zapped badly every time I stepped out of that thing when driving in dry weather:)
everything connected to the high voltage transmission line needs to, for lack of a better term, resonate in phase and amplitude with the sine wave on the transmission line.
If you introduce resistance or lag elements (inductance) it will cause the familiar power dissipation or sparking.
Just because I have 600V rated insulated shoes still doesn't mean I'm going to successfully put L1 on my tongue from a 3-phase, 480V, 60Hz supply.
There are several voltage stages depending on where you are between your house and the sub-station. I don't know off hand, but my lineman friend said something like the wooden poles are 2700V at 5Amps ... the metal Poles are much higher voltage.
The Helicopter by itself generates an electrostatic charge from the rotating blades that is DC ,,, that is what you are seeing, not the HV from the power line... (I think)
incorrect . The sparks are Littrly charging the helo ...the reason there is not one zap but many is its AC ..
the Helo is Lagging in its voltage just as a Cap does ! .....
The stick is so that the helo can pardon the pun Float at the EHV and become One with the line .....
I did the same with my tesla stunts ,,,,,, We can sit on a platform and Still get zapped by the fact that its AC near a some what conductive object our bodies .... this is why we use wire mesh suits and other trade secrets to keep us safe
Loopy,
those lines are carrying AC. That means they are at a billion volts one millisecond an minus a billion volts 10ms later.
So what voltage does that helicopter reach when it leaves?
And perhaps there is the answer. If the line were DC and the copter was "up to the line voltage" then there would be no spark as it left. Charge will not want to move from place to place at the same voltage.
BUT, as it is AC then as the copter moves away at some point it is charged to, say, plus a billion volts. But then the line is driven down to minus a billion volts. Tick, there is the spark.
Note: In this post "billion" is whatever huge peak voltage that line reaches.
If it was DC there would be One spark ,....
If I did not have bad knees I would SO do that job ..
granted Me and HV have a some what cozy life together .
High tension power lines are certainly NOT billions of volts. I've no idea if it is DC from the helicopter or AC from the power lines, but the men are obviously using a safety procedure to bring them to the same electrical potential as the power line, before they climb onto it.
And it did seem odd to me that they were being dropped off in the middle of the line. But that may be a safer transfer point than nearer to a pole. They may actually then move to the poles where they clean and inspect insulators.
As best as I can recall, power lines directly from a power plants generating facilities are in the low hundreds of KV. I don't think they ever get above a million volts. Most of the distribution network is less than 30KV, but this appears to be a long-distance line that has clusters of three cables that work as one wire.
Here is a better representation of actual voltages... but just for North America. Different countries do different things.
Peter, yes, that's the way I tried to explain it. I should have used the words "capacitive" and "lag" so these techie types understood what I said:)
On the other hand I can well imagine a copter does charge itself up. DC charge not AC. Due to all that friction with the air going on. If storm clouds can do it why not those rotors?
It's just odd then I have never seen the phenomena before having seen a lot of copters landing. And what about the those brave helicopter resusece guys going down from a winch. Never heard mention of anti-static precautions there.
Sure not a "billion" volts. I did define what I meant by that in my post.
I would imagine going for the middle of the line is far safer than being near the pylons what with them being grounded. Have a search on youtube for "pylon eletrocution" to see the horrific results of being to near the pylons.
It may just be that the fact that the helicopter is operating near the high tension wire means that it builds up a much larger charge than it does in normal flight.
They do clean and inspect these lines regularly. Power losses from dirty insulators are significant enough to justify the work.
The first video, the sparks didn't quite seem real, the video may have been chopping them but the frequency didn't even sound quite right.
The second video was much more convincing, but I'm not sure why they were working on this LIVE somewhere in the middle of the line.
It may not always be an option to shut down a High-KV transfer line for maintenance. These lines are bl**dy expensive to build, so redundancy is at the 'bare minimum', and that's usually 'hot' redundancy, too. (No parallell lines, just cross-connects from county to county, or state to state) Shutting down a live line means doing a lot of switching work at a lot of substations. It may switch over flawlessly, or it may not... Very few power companies are willing to take that risk if there's a hospital on one of the circuits. (Or electric furnaces for smelting metals... They tend to crack... or at least will take a week to get back up... )
With one main trunk down, the others will carry a higher load, which puts a bigger strain on the lines and stations.
Also, doing a proper 'switchover' takes time.
Anyway, even if they did 'kill the line', there's no way you'd get a lineman to touch it without doing the exact same safety protocols anyway, as these lines are never really 'dead'.
Some dumb Schmuck may have hooked up a small gasoline generator to his home and not disconnected it from the feed so that it leaks back out(only a issue at the lowest levels), a switch at one of the substations may be broken, there may be improper shielding at the substation and so on.
The grid here in Norway barely has the redundancy needed for normal use. During cold winters parts of it is barely avoiding meltdown.
(building lines across mountains is expensive and very difficult. Maintenance is even worse. Without choppers it would be almost imppossible)
And Norsk Hydro has one of their biggest aluminium smelting plants about 60miles from where I live...
Actually you can get a good zap just walking up to a truck parked under those lines and touching the door handle to open it. You can actually hear a hum from those lines (500,000 volts) when walking under them.
Farmers working under those lines need to be careful to ground metal objects...
Now you remind me. We used to live next to a dairy farm in the south east of England. Lot's of cows and some electric fences to keep there where they should be.
However, one of those electric fences had no "ticker" box. It ran down the middle of a huge field directly under the overhead power cables that were supplying power to the nearby city of Canterbury.
It did it's job very well!
Its NOT static ! ...... take a blimp in place of a helo and the same can occur.
you are gonna get AC phase Tweaked discharges . just as Heater described .... Its just Lag ! .
ANY metal no matter how small has capacitance and for that matter at HV it does not need to be copper ..... mositure alone can behave as a Cap plate!
Ask the people at LAPP ..
and with HV you have a Voltage gradient that Like a greyscale goes from HV to GND ( some times phase to phase )
If you have 1 MegV at one meter above GND you have set up a gradentst ,. and that is DC ....
so If you were to have a Infintite ohm inpout meter and stuck it at 500 CM . you would get 500 kV ( with res;pect to GND)
with AC the gradient is expanding and collapsing at 60 HZ
Soooo at the same point with AC ... 1/120th of a sec the 500 kV point is positive and the next its negitive ...
You have a object there that is not air ... Its gonna GAIN a charge just as a cap does .
remember the world is the other plate .......
Birds are 80% water line us ( a plate or a object ) . the same shock that charges that helo can give a zap to the bird .....
those non contact voltage indicators use the same idea with a FET as a input ,,,,,,
the voltage in your home makes a darn small gradients..... but at nasty 400kV the gradients is HUGE .......
Ill head to the lab and show you at 15kV how I can draw a buzz to a metal isolated sphere this afternoon ..
toss EE 101 out the door ., once you get in to HV the rules are not allwas the same
You can light up a fluorescent tube underneath a HV power line, just by holding it in the air vertically. (Not stupidly high to the point it would arc down).
It's that same voltage gradient effect at work.
I did some drainage tubing work in a field crossed by HV lines back in the 80's.
Getting on and off of tracked equipment like a dozer near the line was no problem, but rubber tired equipment would occasionally bite you if you didn't leave a chain dragging.
On humid mornings the line would sizzle like frying bacon.
Excavated the expansion of the Moscone Center in San Francisco and the north side of the pit had major underground HV power lines for BART. We had a bit of ground shifting and water. People were getting shocks from walking on that side of the site.
I never did find out how the problem was resolved. It may just have been water seepage into the wrong places. But more and more HV has gone underground in big cities.
Excavated the expansion of the Moscone Center in San Francisco and the north side of the pit had major underground HV power lines for BART. We had a bit of ground shifting and water. People were getting shocks from walking on that side of the site...
I read somewhere that if a high voltage power line is down and touching the ground near you, that you should not "walk away" from it... Rather "bunny hop" away from it (with both feet together). That is because the high voltage is flowing through the ground and could take a path up one leg and down the other if your feet are apart.
Ron Czapala
Posts: 2,418
Comments
Um, no thanks!
...roger THAT!!! O_o
They used a probe to bring the helicopter up to the line voltage, then attached a cable while they climbed on and transferred gear.
The second video was much more convincing, but I'm not sure why they were working on this LIVE somewhere in the middle of the line.
Loopy Byteloose, there was also a spark at the very beginning as the helicopter approached.
I know two people (Lineman) that have lost arms and or legs because they became a human fuse. If the first video is is truly part of the training, then I pray for the families, but in the same breath. With something that serious, you don't cut-up and laugh about it. "Playing" with that kind of power is just asking for trouble - be careful what you ask for.
So what voltage does that helicopter reach when it leaves?
And perhaps there is the answer. If the line were DC and the copter was "up to the line voltage" then there would be no spark as it left. Charge will not want to move from place to place at the same voltage.
BUT, as it is AC then as the copter moves away at some point it is charged to, say, plus a billion volts. But then the line is driven down to minus a billion volts. Tick, there is the spark.
Note: In this post "billion" is whatever huge peak voltage that line reaches.
EDIT: Wiki says something different about voltages....
http://en.wikipedia.org/wiki/File:Electricity_grid_simple-_North_America.svg
The Helicopter by itself generates an electrostatic charge from the rotating blades that is DC ,,, that is what you are seeing, not the HV from the power line... (I think)
That does not sound right either to me.
If a helicopter "generates an electrostatic charge from the rotating blades that is DC" then we would be used to seeing such a spark show everytime a helicopter landed. We do not.
http://en.wikipedia.org/wiki/Helicopter_support_team
Well, OK, normally when a copter lands there is nobody standing under it ready to get zapped. On the other hand we don't seem to see sparks as in the video jumping between copter and ground.
Now I wish my old car had a "static man". I used to get zapped badly every time I stepped out of that thing when driving in dry weather:)
If you introduce resistance or lag elements (inductance) it will cause the familiar power dissipation or sparking.
Just because I have 600V rated insulated shoes still doesn't mean I'm going to successfully put L1 on my tongue from a 3-phase, 480V, 60Hz supply.
1) A quadcopter.
2) with a video camera on board.
3) A gold leaf electroscope.
If so could they carry the electroscope up with the copter and watch it with the camera?
If the copter is becoming charged, as we might exepect from the arguments above, we should see the gold leaves move as it takes off and lands.
incorrect . The sparks are Littrly charging the helo ...the reason there is not one zap but many is its AC ..
the Helo is Lagging in its voltage just as a Cap does ! .....
The stick is so that the helo can pardon the pun Float at the EHV and become One with the line .....
I did the same with my tesla stunts ,,,,,, We can sit on a platform and Still get zapped by the fact that its AC near a some what conductive object our bodies .... this is why we use wire mesh suits and other trade secrets to keep us safe
If it was DC there would be One spark ,....
If I did not have bad knees I would SO do that job ..
granted Me and HV have a some what cozy life together .
And it did seem odd to me that they were being dropped off in the middle of the line. But that may be a safer transfer point than nearer to a pole. They may actually then move to the poles where they clean and inspect insulators.
As best as I can recall, power lines directly from a power plants generating facilities are in the low hundreds of KV. I don't think they ever get above a million volts. Most of the distribution network is less than 30KV, but this appears to be a long-distance line that has clusters of three cables that work as one wire.
Here is a better representation of actual voltages... but just for North America. Different countries do different things.
http://en.wikipedia.org/wiki/File:Electricity_grid_simple-_North_America.svg
On the other hand I can well imagine a copter does charge itself up. DC charge not AC. Due to all that friction with the air going on. If storm clouds can do it why not those rotors?
It's just odd then I have never seen the phenomena before having seen a lot of copters landing. And what about the those brave helicopter resusece guys going down from a winch. Never heard mention of anti-static precautions there.
This calls for an experiment, as described above.
Sure not a "billion" volts. I did define what I meant by that in my post.
I would imagine going for the middle of the line is far safer than being near the pylons what with them being grounded. Have a search on youtube for "pylon eletrocution" to see the horrific results of being to near the pylons.
They do clean and inspect these lines regularly. Power losses from dirty insulators are significant enough to justify the work.
I agree with the answer here:
http://www.madsci.org/posts/archives/2007-02/1170981977.Ph.r.html
It may not always be an option to shut down a High-KV transfer line for maintenance. These lines are bl**dy expensive to build, so redundancy is at the 'bare minimum', and that's usually 'hot' redundancy, too. (No parallell lines, just cross-connects from county to county, or state to state) Shutting down a live line means doing a lot of switching work at a lot of substations. It may switch over flawlessly, or it may not... Very few power companies are willing to take that risk if there's a hospital on one of the circuits. (Or electric furnaces for smelting metals... They tend to crack... or at least will take a week to get back up... )
With one main trunk down, the others will carry a higher load, which puts a bigger strain on the lines and stations.
Also, doing a proper 'switchover' takes time.
Anyway, even if they did 'kill the line', there's no way you'd get a lineman to touch it without doing the exact same safety protocols anyway, as these lines are never really 'dead'.
Some dumb Schmuck may have hooked up a small gasoline generator to his home and not disconnected it from the feed so that it leaks back out(only a issue at the lowest levels), a switch at one of the substations may be broken, there may be improper shielding at the substation and so on.
The grid here in Norway barely has the redundancy needed for normal use. During cold winters parts of it is barely avoiding meltdown.
(building lines across mountains is expensive and very difficult. Maintenance is even worse. Without choppers it would be almost imppossible)
And Norsk Hydro has one of their biggest aluminium smelting plants about 60miles from where I live...
Farmers working under those lines need to be careful to ground metal objects like irrigation pipes and fences. Here is a flyer on that...
http://transmission.bpa.gov/lancom/Living_and_Working_Around_High_Voltage_Power_Lines_11-07.pdf
The transmission lines which are 1 million volts look like the following, have about 6 wires per "line", and have very long insulators...
http://tdworld.com/transmission/indias-powergrid-rd-efforts
Then something interesting is a "Single Wire Earth Return" transmission line where just 1 wire is run and the "earth" is used as the other "conductor"...
http://en.wikipedia.org/wiki/Single-wire_earth_return
Now you remind me. We used to live next to a dairy farm in the south east of England. Lot's of cows and some electric fences to keep there where they should be.
However, one of those electric fences had no "ticker" box. It ran down the middle of a huge field directly under the overhead power cables that were supplying power to the nearby city of Canterbury.
It did it's job very well!
THAT is the most irresponsible 'electric fence' setup I have ever heard of!
It's also completely illegal...
you are gonna get AC phase Tweaked discharges . just as Heater described .... Its just Lag ! .
ANY metal no matter how small has capacitance and for that matter at HV it does not need to be copper ..... mositure alone can behave as a Cap plate!
Ask the people at LAPP ..
and with HV you have a Voltage gradient that Like a greyscale goes from HV to GND ( some times phase to phase )
If you have 1 MegV at one meter above GND you have set up a gradentst ,. and that is DC ....
so If you were to have a Infintite ohm inpout meter and stuck it at 500 CM . you would get 500 kV ( with res;pect to GND)
with AC the gradient is expanding and collapsing at 60 HZ
Soooo at the same point with AC ... 1/120th of a sec the 500 kV point is positive and the next its negitive ...
You have a object there that is not air ... Its gonna GAIN a charge just as a cap does .
remember the world is the other plate .......
Birds are 80% water line us ( a plate or a object ) . the same shock that charges that helo can give a zap to the bird .....
those non contact voltage indicators use the same idea with a FET as a input ,,,,,,
the voltage in your home makes a darn small gradients..... but at nasty 400kV the gradients is HUGE .......
Ill head to the lab and show you at 15kV how I can draw a buzz to a metal isolated sphere this afternoon ..
toss EE 101 out the door ., once you get in to HV the rules are not allwas the same
I agree with you... just stay safe.
You can light up a fluorescent tube underneath a HV power line, just by holding it in the air vertically. (Not stupidly high to the point it would arc down).
It's that same voltage gradient effect at work.
Getting on and off of tracked equipment like a dozer near the line was no problem, but rubber tired equipment would occasionally bite you if you didn't leave a chain dragging.
On humid mornings the line would sizzle like frying bacon.
C.W.
I never did find out how the problem was resolved. It may just have been water seepage into the wrong places. But more and more HV has gone underground in big cities.
I read somewhere that if a high voltage power line is down and touching the ground near you, that you should not "walk away" from it... Rather "bunny hop" away from it (with both feet together). That is because the high voltage is flowing through the ground and could take a path up one leg and down the other if your feet are apart.