Question About How Getting Electrocuted Works

[bostonman]

Regardless of safety, at 300+ volts in a car, lethal accidents can happen.

In any case, I didn't mean to deviate. My comment was pointing out that I was unaware of the high voltage in cars.

What about the question I had regarding a hypothetical situation with sitting on a power line? Would capacitance cause death or just a shock?

[Andy Chee]

Would I get a a 10kV jolt in my body that would kill me due to a difference in voltage potential (my body is at "0V" and the power line is at 10kV) or would I just sit on the wire and not feel anything?

Just like a bird, you would sit on the wire and not feel anything.

HOWEVER

If you use a helicopter, the rotating blades may create static electricity, as seen in this video:



Note the static discharge rod in the left hand, and the grounding clamp in the right hand.

Here's another

[IanB]

If you use a helicopter, the rotating blades may create static electricity, as seen in this video:

I don't think that's static electricity. I think that is capacitive coupling between the wire and the helicopter.

If it were static electricity, it would just be a single spark like from an electrostatic machine. This is not a spark, it is a continuous buzzing arc.

[Berni]

The arc you see with the helicopter connecting onto the lines is capacitive coupling. Tho static buildup from the blades is also a thing with helicopters (but is not anywhere near this intense)

This is the main reason why they have to connect the helicopter to the line and why the workers wear special conductive suits. This conducts the AC coupled currents around the people rather than trough them. If you were to reach out with your bare hand at the line you would get quite the zap. Making things worse zaps make you jump and that's the last thing you want to be doing when you are climbing on a wire high in the air.

Main problem being is that the arc works as a 'interrupting switch' So that the self capacitance brings the two sides many kilovolts apart, then at one point the arc forms and dumps those kilovolts into the capacitance over a very short period, this causes very high peak currents in the many amps. This is indeed similar to a static shock. Not quite so dangerous due to the short duration, but is very painful, now imagine that happening 120 times per second.

This is also likely why birds don't like the higher voltage lines, they get a shock when getting close, but id assume once the bird is perched on the line and connected fully it would be fine.

[Haenk]

Getting electrocuted is rather an indirect death - your heart will stop beating.
Stopping the current flow and then using reanimation has a good chance of surviving the incident. That's probably the cause of not too many deaths by electricity.

The electric chair does not work by simply stopping your heartbeat, you are getting cooked. Which, of course, is an awful death.

[jpanhalt]

The electric chair does not work by simply stopping your heartbeat, you are getting cooked. Which, of course, is an awful death.

Are you sure it's not just the optics?  However, like others here, I have had non-lethal shocks, and they are not pleasant.

Capital punishment in the US is a hot topic and whether it should continue is not appropriate to discuss here.  However, there are academic studies by pathologists that try to predict how much awareness of pain the subject has.  Hanging and decapitation appear gruesome but were considered humane; however, they are subject to being botched.   An argument can be made that no death is painless, but that's an impossible postulate to test.

Asphyxiation by nitrogen is being considered in some states and has been used by one.  Studies have been done with medical students (believe it or not) in which student volunteers' expired air was passed through NaOH in water to absorb CO2 and then re-inhaled.  As the students went unconscious, they were immediately revived with oxygen.  They had no recollection of going unconscious.  It was reported that some were even surprised to find pencils they were holding had fallen on the floor.

[pcprogrammer]

On the subject of death and pain there is indeed no way of assuring someone who died did not feel pain, but if anesthetics are used I think it is safe to say that no pain was felt.

I have had surgery under full anesthetics once, and have no recollection of feeling any pain during the time I was under, so my guess is that you don't feel pain when they euthanize you with the use of anesthetics followed by for instance cyanide or other quick working poison.

Both my parents have been euthanized and I witnessed both going of in nowhere land without any sign of discomfort. Something to consider for the states that still feel the need to use capital punishment.

[jpanhalt]

Most anesthetics block pain. Nitrous oxide is used an example with limited pain blocking.  However, things happen where there is likely pain, but you don't perceive it.  Grabbing a mouse by the nap of the neck  (as when a bird of prey grabs it or as used in a laboratory) may block awareness, but not pain itself. 

My personal experience includes an accident when descending on an extension ladder that collapsed.  I fell backwards and landed on my back on the ladder somehow, broke several ribs, and was probably unconscious for an unknown period. All I remembered was the sensation of falling.  No pain from the landing or injuries as they occurred.  Our bodies have a way of blocking such memories.  It's like the philosophical question of whether a tree  falling in the woods makes a sound if no one is around to hear it.  If you don't perceive pain, was there pain?

Nitrogen has the the property of causing narcosis (e.g., raptures of the deep), which may be important in the use as mentioned.

[bostonman]

This is also likely why birds don't like the higher voltage lines, they get a shock when getting close, but id assume once the bird is perched on the line and connected fully it would be fine.

The rotating blades would make sense as to why a build up exists, but I'm a bit mixed up on capacitance coupling versus static electricity.

Again, ignoring ground and arcing, assuming I can just fly up to a single power line, and let's even call it 1M (million) volts. What exactly would happen to me? Since my body is at (let's assume 0v), does that mean an instant 1M volts would transfer into my body thus giving me the shock of my life? If so, why would that not kill someone?

[IanB]

Again, ignoring ground and arcing, assuming I can just fly up to a single power line, and let's even call it 1M (million) volts. What exactly would happen to me? Since my body is at (let's assume 0v), does that mean an instant 1M volts would transfer into my body thus giving me the shock of my life? If so, why would that not kill someone?

1 MV isn't going to happen on an AC power line, but just for grins, let's assume 500 kV. What that means is the wire is going to change in potential from +400 kV to −400 kV, 60 times per second. That's a peak to peak voltage swing of 800 kV.

So if you were to touch that wire, your body is also going to swing up and down by nearly 1 million volts, not just once, but 60 times per second. I dare say you would find that experience rather exciting 

[bostonman]

I was using 1M volts as a nice round number; and exaggerated for purposes of discussion.

So a person wouldn't get electrocuted, but would oscillate at 60Hz with a 800kV p-p swing?

Does that mean eventually the person would charge to the same potential and not feel the really cool and exciting feeling?

[johansen]

the capacitive reactance of 100 pf is 25 megaohms at 60hz.

so 500k volts results in 20 milliamps.

https://incompliancemag.com/human-body-model-and-electrostatic-discharge-esd-tests/

so the minimum capacitance in free space is apparently 55pf. --plus corona losses.

have fun with that. at 69,000 volts (typical high voltage before the 7.2kv substations) you ll have 1.5mA minimum, hanging off the line. good for a bit of a tickle.

[Andy Chee]

Since my body is at (let's assume 0v), does that mean an instant 1M volts would transfer into my body thus giving me the shock of my life? If so, why would that not kill someone?

Your assumption is incorrect, a flying human body is NOT at ground potential..... they are not touching ground!

An isolated flying human body can float to any voltage, much like how an isolated multimeter can float to any voltage without damaging itself.

[donlisms]

I googled “bird power meter.”  I thought it might be relevant. Seems like an open business opportunity.

[Berni]

I was using 1M volts as a nice round number; and exaggerated for purposes of discussion.

So a person wouldn't get electrocuted, but would oscillate at 60Hz with a 800kV p-p swing?

Does that mean eventually the person would charge to the same potential and not feel the really cool and exciting feeling?

The problematic part is when you get close but not actually touch the high voltage line.

That's where you get the arcing happen, so if the line swings between +400kV and -400kV, at the peaks you would get an arc jump from the line to you charging you up to +400kV then as the line swings the other way you get an arc from the -400kV line to your body charged to +400kV so this is the same as if you stood on a insulator charged to 800kV and touched a grounding rod, sending 10s or 100s of amps trough your body (but only for a very very short time). Most static shocks that properly hurt are only a few 10s of kV, so this would be 10x more painful than the worst static shock you had before, and it would be experiencing it again and again up to 120 times per second! Id say this would hurt worse than grabbing 220V mains.

Once you actually grab into the line it should be a lot better. At that point arcing stops and the current being pushed into your body becomes a smooth sine wave (~90 degree out of phase with voltage) and the peak current should drop to miliamps. If you grabbed on with your whole hand then it likely wouldn't be more than a tingle. If you instead just pressed the tip of your finger against the line then it would certainly be a unpleasant sting. Tho at these sort of voltages you also might start feeling weird stings over your body from corona discharge sending electrons into the air(I hope you are not wearing jewelry).

The brave linemen that climb on these lines are connected to the line and are clearly alive. They just have conductive suits to keep these currents from being actually felt by them.

[bostonman]

I learned a bit more from this thread.

I have a foot pedal that enables the AC outlet only when pressed. Usually I'll use it when working inside something that's AC in hopes that if I get shocked, my foot comes off the pedal.

After reading this thread, seems my leg muscles may tighten and continue pushing on the pedal.

As for capacitance, again, assuming no ground exists for a far distance, an animal or human can touch the live wire, but all they'll experience is a continuous oscillation of 60Hz (50Hz elsewhere) that will be unpleasant but not kill them?

If I understand correctly, if the voltage is high enough, then it can arc through the air and the person will get electrocuted.

Did I understand everything correctly?

[IanB]

After reading this thread, seems my leg muscles may tighten and continue pushing on the pedal.

Only if electric current is passing through your leg muscles. Muscles contract because the electric current activates the muscle fibers.

As for capacitance, again, assuming no ground exists for a far distance, an animal or human can touch the live wire, but all they'll experience is a continuous oscillation of 60Hz (50Hz elsewhere) that will be unpleasant but not kill them?

It's not clear what the impact would be. It depends on the voltage on the wire. Since no human can fly up to a 400 kV wire unassisted and touch it with their bare hand, it's not clearly known what the effect would be.

If I understand correctly, if the voltage is high enough, then it can arc through the air and the person will get electrocuted.

The air doesn't make a difference to electrocution potential. It hurts to get zapped with a spark or arc, because it is hot, and because the effect is concentrated on a small contact area with a big current spike. If you touch the conductor there is less pain because the current is spread out over more area and averaged over time.

Nevertheless, if the voltage is high enough, and your capacitance is high enough, the reactive current might be enough to hurt or kill you. This is not an experiment anyone wants to try.

[pcprogrammer]

Maybe this mythbusters episode brings some light to the subject 



I saw it a long time ago and can't fully recall the outcome, but it probably also depends on if anything in the tub is conductive to ground. I expect the results to be different when a polyester tub with pvc drains is used.

[bostonman]

It states the video "wasn't made available in our country".

That's an odd message that I haven't seen.

[pcprogrammer]

It states the video "wasn't made available in our country".

That's an odd message that I haven't seen.

You can search for mythbusters season 2 episode 11, or mythbusters bathtub electrocution.

[tooki]

1 MV isn't going to happen on an AC power line, but just for grins, let's assume 500 kV.

What are you talking about?! 1MV transmission lines have been in use for many years. Both DC and AC examples exist. The USSR installed a network of 1.15MV AC lines back in the 1980s, but was reduced to 500kV when the USSR dissolved. Japan has another network of lines currently operated at 500kV, but designed for 1.1MV if needed later. And China has a large network of ultra high voltage transmission lines in operation (most are either 1MV AC or ±800 kV bipolar DC, but one is ±1.1MV DC).

[bostonman]

I stand corrected.

I was tossing out some high voltage number for purposes of discussion, but assumed it didn't exist.

My question(s) were more of: without the ability to conduct hot to some neutral or ground, would I feel anything sitting on a power line, so I threw out 1MV as an example.

[IanB]

1 MV isn't going to happen on an AC power line, but just for grins, let's assume 500 kV.

What are you talking about?!

We are talking about AC transmission lines. Not DC.

The highest voltage in use in the USA is 765 kV. In other parts of the world, AC transmission lines operating at voltages 1 MV and above are rare and unusual to the point of being a special talking point.

[jmelson]

shorting sticks to safely raise the worker and the helicopter to the same potential as the line.

Now I'm intrigued as to the average capacitance of a helicopter

It can't be a whole lot, but the arcs when the grounding clamp is brought to the HV wire are QUITE impressive!  The guys who do this work wear a wire mesh suit that is grounded to the grounding clamp.
Jon

[tooki]

1 MV isn't going to happen on an AC power line, but just for grins, let's assume 500 kV.

What are you talking about?!

We are talking about AC transmission lines.

You said 1kV AC is “not gonna happen”. Well it can happen, and is in fact in use.

Not DC.

Did you even read my entire post before barking back? It is 1000% clear that I know that, since I explicitly mention 1MV AC lines and contrast with DC ones, too.

The highest voltage in use in the USA is 765 kV. In other parts of the world, AC transmission lines operating at voltages 1 MV and above are rare and unusual to the point of being a special talking point.

So? The fact is, you said 1MV AC can’t be done, but it can. The same laws of physics apply everywhere. The fact that it isn’t done commonly, or that it isn’t in use in USA, does not change the fact that 1MV AC is doable, and not just in theory, but in practice.


P.S. “What are you talking about?” is also an expression meaning as much as “where’d you get that incorrect idea?” When, like here, the rest of the response clearly indicates that the person knows the topic of discussion, you should know that it isn’t a query meaning “please name the topic of discussion”.