depends on where and when
power lines might be aluminum wires along with a steel wire.
lines to a building, if three cables separated by air, may have been insulated though deteriorated over time and the insulation now missing.
And even if the power line is completely disconnected from the substation, it can still be charged: if some guy is running a generator for his house and it’s not hooked up correctly, it will power up all the lines connected to the house. So even if there’s a complete blackout, don’t go screwing with downed power lines.
OK it’s a nitpick but I’m a power engineer and it just bugs me when people say this.
ALL power lines ARE insulated.
It’s just that not all conductors have an insulating sheath (the plastic /rubber looking stuff)
They are insulated at the pole by, wait for it, INSULATORS which are usually made out of glass, porcelain, or plastic. They are insulated everywhere else by AIR. That’s pretty much the purpose of putting them high up on poles. They only need a few inches (or feet for high voltages) to be insulated. The rest of the space is to keep people, plants, and constructed objects from getting within that dangerous few inches that would cause the current to flow through the wrong things (people, houses, bushes, etc).
Most power lines are ACSR (Aluminum Cable Steel Reinforced) - Steel cable in the middle with aluminum strands wrapped around it)
And most house drops (the cable from the pole to the house) is sheath insulated. The closer the cable gets to the ground (and people) the more need for sheath insulation.
If a hot line is draped over your car, can you drive out from under it without bodily risk? I would guess so, because the outside of the car would complete any circuit, as a Faraday cage, and besides most of what the driver touches is pretty insulative. This might be safer than staying still in the car, given that outside conditions could change. Anybody have good enough information to act on?
I know you said “as” as a Faraday cage, but the Faraday cage protects against static discharge and electromagnetic fields. I do not know that it will protect the occupants against an electrical current flow. I would guess, however, that you are probably still safer in the car rather than stepping out and grounding yourself, in which case touching the car (which is being touched by the line) would fry you.
to drive your auto you need to touch the steering wheel, shift lever and pedals, any or all may be energized with electricity, even though they may have a plastic or rubber spot to touch you are placing your body closer to metal that could have tens of thousands of volts on it. if you aren’t dead then sit still, any movement may place you close enough to energized metal to become a electrical current path.
You know perfectly well that sheath insulation is the sort relevant to people who aren’t engineers or electricians, and the sort they mean when they use the word.
This video of a fallen power line setting a row of cars on fire was in the “related videos” section for one of the videos linked to earlier in the thread.
Any practical advice on what to do if a fallen power line has just set your car on fire?
Squirrels place their bodies against lines with tens of thousands of volts on it but don’t have any problem unless they touch something else with a different potential. What do you mean by “energized with electricity”?
the metal car parts including controls may have tens of thousands of volts on it, if you are well separated from it you may not have a problem. touching the controls puts you very close to that high voltage, close enough that you could draw an arc. your body is large and while sitting is touching a lot of materials, a voltage potential difference is likely to occur.
If you’re sitting in the car, the voltage is going right through you regardless of what you touch. That’s not a problem until you open the door and put your foot on the ground.
And if you are caught, you will get a big fine (possibly some jail time) and a really big restitution order!
Wrong.
Every point in/on the car will be at a different potential with respect to ground. And therefore at a different potential with respect to each other. The car’s skin will also in general be at a different potential than some mechanical part such as the gear shift.
If two parts of your body touch two parts of the car, you’ll feel the potential difference between those two parts as a current flow through you.
Given 10,000 volts at, say, the center of the roof, you could easily have a 1,000 volt potential difference between, say, the door handle and the gear shift.
To be sure, one hand on the roof metal and one foot on the ground would be a much bigger difference, pretty much the full 10KV. But to say that you *must *have some body part touching the ground to receive a shock is completely misguided.
Voltage doesn’t “go through”. More accurately, you’re at a voltage of tens of thousands of volts (or whatever) relative to the Earth.
And guizot, one of the tactics used by the US military is to dump strips of metal out of an aircraft over a city to deliberately cause a blackout by shorting power lines (it’s speculated that this might have been done in the bin Laden raid, though I suspect that there they just waited for a blackout to happen anyway).
??? Considering the resistance of the metal in a car, it will be low. You would have to have a high current flow through the metal and it would begin to glow.
Mmmmm, no. The different in potential between say the gear shift lever (assuming a stick shift with the lever coming right out of the trans here) and the body of the car will be negligible. Pretty much all the metal in the car is tied together because almost all electrical items in the car use the closest piece of metal for the ground conductor in the car’s electrical system. In other words damn near any piece of metal you can name in the car is going to be electrically tied to every other piece of metal in the car.
I doubt you could drive out from under the wire as the high voltage will probably play havoc with the car’s electronics.
Forgive me for my attempt to fight ignorance. Is this the wrong place for that? :rolleyes:
Ignorance of the distinction between common usage and insider usage? Yes.
But in a discussion about downed power lines, I’d rather hear the words of an engineer in the field over the dozens of guesses and jokes that often litter GQ threads.
I usually find nitpicks annoying, but this one doesn’t bother me at all.
I think in GQ it’s not improper to try to be as correct as possible.