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Okay this issue has been bothering me immensely so hopefully someone will be able to help me out or steer me in the right direction.

Lets say hypothetically I possessed an absolutely perfectly insulating chair and I stood on it and then touched the hot wire of a three prong socket, would I get shocked? My existing knowledge tells me that I will get 'somewhat' of a shock. This will be because a human body has a non-zero capacitance and so charge will flow onto and off me sequentially in sync with the frequency of the mains supply as it oscillates my potential up and down with the wire that I am presumed to be touching. The question of whether this oscillating current into and out of my body at say 50Hz will shock me severely or not depends on the capacitance of my body. If my capacitance is extremely low (as is the case for a bird perhaps), then the shock and the sensation all together would probably be minimal. If I were a large animal like an elephant then the current would be greater since my capacitance would be greater. So my question becomes : Is the capacitance of a human body great enough to cause a severe shock in this case?

Now if this is all true and my suppositions are correct then why does a high voltage repairman have to wear a Faraday cage type suit (as in the case in this video https://www.youtube.com/watch?v=9YmFHAFYwmY). Is this because the voltage is so high and the capacitance of the helicopter is very large so that immense current flows back and forth during each oscillation? Because of this immense current, both the repairmen and the pilot must wear a Faraday cage suit to ensure that the current flows around their bodies via the skin effect? If they did not wear those Faraday cage suits then they would surely be shocked to death since the arc between the wand they use to initially touch the line shows that the current going into and out of the helicopter as well as the potential difference between the line and the helicopter is immense (surely enough to kill them both). So then I ask, well if the Faraday cage suit is what is protecting them from severe potentially fatal shocks, then why do electricians not wear them when working? If my belief about the Faraday cage suit being the primary protection of the high voltage line repairmen is true, then surely if I wore one and touched the live wire of a three pronged socket whilst perfectly grounded I should be completely immune to a shock?

Any help on this would be greatly appreciated!

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  • \$\begingroup\$ To my understanding, yes. Your faraday suit would still heat up though. \$\endgroup\$ – DKNguyen Sep 3 at 16:15
  • \$\begingroup\$ Related: physics.stackexchange.com/questions/191503/… - evidently because corona discharge from the lines can be injurious when exposure is prolonged. \$\endgroup\$ – Adam Lawrence Sep 3 at 16:39
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    \$\begingroup\$ Also: en.wikipedia.org/wiki/Live-line_working - "The strong electric field surrounding charged equipment is enough to drive a current of approximately 15 μA for each kV·m−1 through a human body. To prevent this, hot-hand workers are usually required to wear a Faraday suit. This is a set of overalls made from or woven throughout with conducting fibers. The suit is in effect a wearable Faraday cage, which equalizes the potential over the body, and ensures there is no through-tissue current.Conducting gloves, even conducting socks, are also necessary, leaving only the face uncovered." \$\endgroup\$ – Adam Lawrence Sep 3 at 16:44
  • \$\begingroup\$ Helicopters can also develop substantial electric charge just by flying along minding their own business. I guess it is just the rotors moving fast in the air. When they do rescues with metal cables, they usually try to discharge by dragging the cable so nobody gets a big shock. \$\endgroup\$ – mkeith Sep 3 at 17:41
  • \$\begingroup\$ The technician that replaced my electricity meter has an isolating floormat as part of his protection equipment. When asking about the fact that he was not wearing his protecting gloves, he said that with that floormat he equally safe. I agree that the isolating floormat is a good protection, but wearing gloves also helps in other cases (he could be touching the wall with one hand and a hot wire with the other). it is less praticle to work - I am sure he prefers finishing earlier. Faraday suits and any other protections face the same "issue": it's cumbersome (and they have a price tag). \$\endgroup\$ – le_top Sep 3 at 20:16
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Doesn't seem to bother these little guys....

enter image description here

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  • \$\begingroup\$ Apparently it does on extremely high voltage lines. They get zapped before the even land so I'm told. \$\endgroup\$ – DKNguyen Sep 3 at 16:30
  • \$\begingroup\$ Maybe - I'm not a bird expert. But those are some very high voltage lines they're sitting on above. What do you mean by "extremely high voltage"??? \$\endgroup\$ – Kyle B Sep 3 at 16:30
  • \$\begingroup\$ >200kV electronics.stackexchange.com/a/430867/212967 \$\endgroup\$ – DKNguyen Sep 3 at 16:31
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    \$\begingroup\$ Paul Harrow response makes sense. They're not getting electrocuted, but they get 'zapped' from coronal discharge. I could see that being painful LOL en.wikipedia.org/wiki/…. \$\endgroup\$ – Kyle B Sep 3 at 17:07
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    \$\begingroup\$ Right. So I guess then the answer to your original question "Can you get shocked if you touch a hot wire whilst perfectly electrically insulated?" is yes. But not due to capacitive coupling to the ground, but rather through coronal discharge to the surrounding air. The suits that linemen wear (and this is pure conjecture) may not be acting as a Faraday cage, rather they are designed with no sharp protrusions that would induce a coronal discharge. \$\endgroup\$ – Kyle B Sep 3 at 20:55
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The capacitance thru shoes is about 30 picoFarad.

This value is from C _parallel_plate = Eo * Er * Area/Distance, with Eo ~ 9e-12 farad/meter, Er = 5 (leather, plastic), Area = 10cm by 30cm, Distance = 1cm

The current at 117vac 60Hz is, using I = C * dV/dT, { from Q = C * V }

I = 30 pF * [160 volts (at sinusoid peak) * 377 radians/second]

I = 30e-12 * [160 * 377] ~~ 30e-12 * 60,000 == 1800 * nanoAmp = 1.8 microAmps

Which over 1,000X weaker than risk to heart.

But a tingle to the skin?

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My strong belief is that you would not get any shock at all if you were standing on a theoretical perfect insulator chair and touched only the hot wire (assuming potential to ground of less than 250V). I am not certain why the linemen wear Faraday suits but I have seen video of personnel transfer from helicopter to high-tension line. There is continuous discharge from helicopter to electrical line (for some reason). They use a cable to shunt the continuous discharge without arcing for the duration of the transfer operation. The arcing resumes as the helicopter flies away after depositing the personnel.

I am just going to be honest and say I don't know for sure why there is arcing between the line and the helicopter. Is it because of the triboelectric effect of the helicopter rotor moving through the air? Is it corona discharge? But whatever the reason, I can see why the line workers would not want it to originate at their skin or flow through their bodies, so it makes sense to wear the Faraday suit.

By the same token, I have NOT observed spontaneous arcing while working on the electrical system in my home or elsewhere. So whatever the cause of arcing on high tension lines, I don't think it is applicable to scenarios inside the home when voltage is below 250V (or even higher, really...)

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