I think we all can see that:
1) A helicopter can probably generate significant static charge by virtue of it's rotors rubbing against all that air.
2) A helicopter, being a big capacitor, can attract huge sparks from AC power lines. After all a 100 thousand volts can break down 15cm of air. As the chopper is not grounded we can double that as the AC goes plus and minus 100 thousand volts.
Question is, what is the significant effect we see in those videos?
As I don't have a chopper at hand to play with, and messing with power lines might get me into some trouble anyway I cannot do the experiments.
I would be happy if someone had a video of such sparks comming from chopper to ground. Otherwise I put the spark show down to the voltage of the AC power line.
Still, in the original vids here we saw similary sized sparks from gloves to line when the guys were grounded by standing on a cherry picker. The AC line voltage is clearly responsible for that. We can expect double sized sparks against an ungrounded heli, as I said above.
Which leads me to an interesting idea I read some years ago and goes like this:
1) Perhaps one can survive spark hits from Tesls coils of "a billion volts". Basically because there is so little current behind it.
2) BUT. If your PSU breaks down then the low voltage mains has a low resistance pathway across a lot of air and through your body provided by the ionization of that "billion volt" spark. Poof you are dead.
Not having a tesla coild around to test that leathal idea with I wondered what else we could do. I need to do an experiment with a simple neon lamp. Connecting 12 volts or so across that will obviously not generate any current and the lamp will not light. But then if we dropped 100 volts (through a current limiting resistor) across that at the same time we might expect the neon to light up and a low resistance path be formed for our 12v PSU. Boom the PSU trips out.
Still, in the original vids here we saw similary sized sparks from gloves to line when the guys were grounded by standing on a cherry picker.
I don't think the cherry picker box is grounded - that would be a disaster. I had some guys trimming my large trees with a cherry picker.
The foreman said the whole boom was made of a heavy plastic in case they accidently touched a power line.
I still stand by my initial remark .. "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 sparks just didn't look realistic from the line-mans gloves to the wire, beside the fact that it was a group of "cut ups" that needed to take their situation a little more seriously if they wanted to survive their job past the first week.
In general, there are three methods of live-line working:[4]
Hot stick
The work is carried out with insulated tools, such as long insulating poles.
Hot glove
The worker is protected by thick rubber gloves, often extending all the way up his arms, and sometimes wears a rubber apron as well.
Hot hand
The worker is transferred to an isolated platform, such as a heavily insulated cherry picker, or suspended from a helicopter, and brought into contact with the equipment.
Some organisations additionally consider working on unearthed de-energised equipment to be another form of live-line working. This is because the line might become inadvertently charged (e.g. through a back-charged transformer), or inductively coupled from an adjacent in-service line. To prevent this, the line is first grounded via a clamp known as a bond or drain earth. Once this is in place, further work is not considered to be live-line working.
Those links to the Kopps-Etchells Effect convince me that satic charge build up on a copter causing sparks is not what we are looking at in the power line video.
Kopps-Etchells seems to be all about the effect when rotors are moving through a cloud of sand and dust that has been stirred up from the ground. There is no such dust cloud up with those power lines.
So I back in the "copter as capacitor near 100KV lines" camp as the cause of those sparks.
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.
Not sure about in the US but in the UK the power station outputs to the metal pylons as high as 400kv this is stepped down by substations to supply local cities /towns substations at 11kv which then step down to 415/230v for factory housing etc.
Kopps-Etchells seems to be all about the effect when rotors are moving through a cloud of sand and dust that has been stirred up from the ground. There is no such dust cloud up with those power lines.
.
This makes sense as anyone who has used a sand blasting machine will attest to, The static build up is quite nasty.
Haha... can't believe someone posted this. I used to do this type of work (15 or so years ago!)
The faraday suit is the key. We called it a shimmy suit in the military. The primary role of it is to prevent the corona effect from ending you. In effect, the suit equalizes potential all around your person so that current does not flow through any part of your person.
The simplest way to picture the concept is to think of all those little tiny birds you see on distribution/transmission lines... they perch nice and happily with no problem at all.
But... ever seen a Condor on a power line? Nope. At least, not many. They're large enough on smaller voltage systems (with only 3-6 feet of space between phases) that the corona effect works really well on them and they become fast blow fuses. The potential at their feet is significantly different than the potential at the tip of their wings. Voila... current flow.
When you see the purple "static sparkles" on the insulators, we call it tracking. That's the corona discharge. The reason for hotwashing is to eliminate the contaminants on the insulators, which build up a conductive pathway for the little ole electrons to flow through.
Those suits have come a long way- but back in the late 90's they were pretty uncomfortable. Like wearing a tee shirt reinforced with a window screen.
I'd like to have worked on a high voltage line, but never got the chance. Our lines were medium voltage, 34.5 kV Delta. Our helicopters were solely analog systems. I'm not sure exactly why, but at the time we couldn't use any digital circuitry because of the grounding strap (the line they attach to the helicopters' faraday suit which was built into the superstructure)
Someone mentioned grounding the heli when it lands- we always had a grounding line out that performed that before anyone got their feet on the ground. Dunno if that's changed since then.
I still stand by my initial remark .. "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 sparks just didn't look realistic from the line-mans gloves to the wire, beside the fact that it was a group of "cut ups" that needed to take their situation a little more seriously if they wanted to survive their job past the first week.
The power line sparks are all chopped up because of the camera used. They're probably using something like a GoPro with a rolling shutter. With direct sun-light the exposure time will be less than 1 mili-second. (so only a narrow line of pixels is being exposed at any time) Add in a bit of aliasing from a 29.7Hz or 25Hz frame rate and it'd be easy to chop up sparks from a 60Hz line like the video shows.
If the audio sounds off, that may also be due to the power line. The field gradients around that line are massive. I would not be surprised if the camera mic directly picked up the EM field.
Still, in the original vids here we saw similary sized sparks from gloves to line when the guys were grounded by standing on a cherry picker. The AC line voltage is clearly responsible for that. We can expect double sized sparks against an ungrounded heli, as I said above.
Which leads me to an interesting idea I read some years ago and goes like this:
1) Perhaps one can survive spark hits from Tesls coils of "a billion volts". Basically because there is so little current behind it.
2) BUT. If your PSU breaks down then the low voltage mains has a low resistance pathway across a lot of air and through your body provided by the ionization of that "billion volt" spark. Poof you are dead.
BINGO !!!!!!!! this is why you don't do non suit stunts . .... If you ever have a primary to Sec flashover you ARE DEAD !!!!!!
I mess with 10 kVA Pole transformers .
I have Drawn 7 footers to my hands. but I am safe from it with my suit I made years ago ..
Ya know I shlud Really get back in to coiling .... no wonder I feel under charged .
Comments
Or you could simply RUN, so that only one foot is in contact with the ground at a time.
I always thought the greater hazards was in one hand and out the other as it crossed your heart.
I suspect most people that sense HV in the ground have no idea what to do and just run. But some may dance quite animately.
1) A helicopter can probably generate significant static charge by virtue of it's rotors rubbing against all that air.
2) A helicopter, being a big capacitor, can attract huge sparks from AC power lines. After all a 100 thousand volts can break down 15cm of air. As the chopper is not grounded we can double that as the AC goes plus and minus 100 thousand volts.
Question is, what is the significant effect we see in those videos?
As I don't have a chopper at hand to play with, and messing with power lines might get me into some trouble anyway I cannot do the experiments.
I would be happy if someone had a video of such sparks comming from chopper to ground. Otherwise I put the spark show down to the voltage of the AC power line.
http://www.youtube.com/watch?v=K3djcxUCcvQ
Still, in the original vids here we saw similary sized sparks from gloves to line when the guys were grounded by standing on a cherry picker. The AC line voltage is clearly responsible for that. We can expect double sized sparks against an ungrounded heli, as I said above.
Which leads me to an interesting idea I read some years ago and goes like this:
1) Perhaps one can survive spark hits from Tesls coils of "a billion volts". Basically because there is so little current behind it.
2) BUT. If your PSU breaks down then the low voltage mains has a low resistance pathway across a lot of air and through your body provided by the ionization of that "billion volt" spark. Poof you are dead.
Not having a tesla coild around to test that leathal idea with I wondered what else we could do. I need to do an experiment with a simple neon lamp. Connecting 12 volts or so across that will obviously not generate any current and the lamp will not light. But then if we dropped 100 volts (through a current limiting resistor) across that at the same time we might expect the neon to light up and a low resistance path be formed for our 12v PSU. Boom the PSU trips out.
I don't think the cherry picker box is grounded - that would be a disaster. I had some guys trimming my large trees with a cherry picker.
The foreman said the whole boom was made of a heavy plastic in case they accidently touched a power line.
I still stand by my initial remark .. "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 sparks just didn't look realistic from the line-mans gloves to the wire, beside the fact that it was a group of "cut ups" that needed to take their situation a little more seriously if they wanted to survive their job past the first week.
Here is a video with a more professional attitude ... The sparks here look and sound more like what I would expect.
http://www.youtube.com/watch?v=EWbBdAeW1m8
http://www.youtube.com/watch?v=lcjhjna9jZE
Pictures of helicopter static discharge from the rotors - the Kopps-Etchells Effect
http://www.chilloutpoint.com/featured/spectacular-helicopter-static-electricity-phenomenon.html
http://www.thefullwiki.org/Live-line_working
In general, there are three methods of live-line working:[4]
Hot stick
The work is carried out with insulated tools, such as long insulating poles.
Hot glove
The worker is protected by thick rubber gloves, often extending all the way up his arms, and sometimes wears a rubber apron as well.
Hot hand
The worker is transferred to an isolated platform, such as a heavily insulated cherry picker, or suspended from a helicopter, and brought into contact with the equipment.
Some organisations additionally consider working on unearthed de-energised equipment to be another form of live-line working. This is because the line might become inadvertently charged (e.g. through a back-charged transformer), or inductively coupled from an adjacent in-service line. To prevent this, the line is first grounded via a clamp known as a bond or drain earth. Once this is in place, further work is not considered to be live-line working.
Kopps-Etchells seems to be all about the effect when rotors are moving through a cloud of sand and dust that has been stirred up from the ground. There is no such dust cloud up with those power lines.
So I back in the "copter as capacitor near 100KV lines" camp as the cause of those sparks.
The faraday suit is the key. We called it a shimmy suit in the military. The primary role of it is to prevent the corona effect from ending you. In effect, the suit equalizes potential all around your person so that current does not flow through any part of your person.
The simplest way to picture the concept is to think of all those little tiny birds you see on distribution/transmission lines... they perch nice and happily with no problem at all.
But... ever seen a Condor on a power line? Nope. At least, not many. They're large enough on smaller voltage systems (with only 3-6 feet of space between phases) that the corona effect works really well on them and they become fast blow fuses. The potential at their feet is significantly different than the potential at the tip of their wings. Voila... current flow.
When you see the purple "static sparkles" on the insulators, we call it tracking. That's the corona discharge. The reason for hotwashing is to eliminate the contaminants on the insulators, which build up a conductive pathway for the little ole electrons to flow through.
Those suits have come a long way- but back in the late 90's they were pretty uncomfortable. Like wearing a tee shirt reinforced with a window screen.
I'd like to have worked on a high voltage line, but never got the chance. Our lines were medium voltage, 34.5 kV Delta. Our helicopters were solely analog systems. I'm not sure exactly why, but at the time we couldn't use any digital circuitry because of the grounding strap (the line they attach to the helicopters' faraday suit which was built into the superstructure)
Someone mentioned grounding the heli when it lands- we always had a grounding line out that performed that before anyone got their feet on the ground. Dunno if that's changed since then.
The power line sparks are all chopped up because of the camera used. They're probably using something like a GoPro with a rolling shutter. With direct sun-light the exposure time will be less than 1 mili-second. (so only a narrow line of pixels is being exposed at any time) Add in a bit of aliasing from a 29.7Hz or 25Hz frame rate and it'd be easy to chop up sparks from a 60Hz line like the video shows.
If the audio sounds off, that may also be due to the power line. The field gradients around that line are massive. I would not be surprised if the camera mic directly picked up the EM field.
Lawson
BINGO !!!!!!!! this is why you don't do non suit stunts . .... If you ever have a primary to Sec flashover you ARE DEAD !!!!!!
I mess with 10 kVA Pole transformers .
I have Drawn 7 footers to my hands. but I am safe from it with my suit I made years ago ..
Ya know I shlud Really get back in to coiling .... no wonder I feel under charged .
You are completely barking mad. Bonkers. Insane.
Love to see one of you shows though:)