Downed power lines

Right. The telephone.

"Grounded" is not at all the same thing as "being on the ground."

What short circuit? Dirt doesn't actually conduct very well, concrete and asphalt even less.

John

Having it both ways I see. So now YOU are going to pick up a hot wire with your bare hands because "Dirt doesn't actually conduct very well, concrete and asphalt even less." and you wouldn't be completing a circuit? Is that your contention? Both of you know damn well that "the earth" is used as a return for power transmission and RF, but you want to claim otherwise when it is convenient for your chicken arguments.

Tell ya what. Next storm, when there are downed power lines, why don't you go do the experiment, and report back here if you survive?

Good Luck! Rich [All standard disclaimers apply.]

On Thu, 13 Jul 2006 15:18:03 GMT, in message , Rich Grise scribed:

Okey dokey, I nominate this for most appropriate response in the thread.

On Thu, 13 Jul 2006 16:40:56 GMT, in message , scribed:

Yes. The power grid is magick, and only dedicated witches and warlocks who have attained the proper levels in the dungeons of Moria are allowed access to the secrets therein. It is sad, but you are not worthy. You *are* the weakest link; goodbye!

On Thu, 13 Jul 2006 10:34:11 -0000, in message , jasen scribed:

That's an excellent observation. In fact, *most* of the electricity will take the path of least resistance, *the rest* will take the other paths available. If you, a human, are part of another path, well....

On Thu, 13 Jul 2006 16:41:18 GMT, in message , scribed:

Ooooh! You are sooooo smart! Please, will you promise to video-capture your super-duper special, not a bolt cutter, cutting tool, when you bite into a 115kV line? Please oh please oh please oh please?!!

On Thu, 13 Jul 2006 16:13:17 GMT, in message , "Bob Myers" scribed:

Well, duh. Everyone knows you need RPN to disarm a warhead.

BTW, I checked that link about "step voltage" and it confirmed my observation that IF you are entering an energized area from the outside, you will get plenty of warning that the step voltage is increasing, and every opportunity to leave the area under your own power (without hopping). The graph shows that the voltage gradient is almost horizontal and increases gradually near the outside edge of the affected area. I don't know how you sleep at night for worrying about the bogeyman.

Hey, to anyone that is still following this thread, Alan is caving. and he is the only one in this discussion with any practical knowledge. Check out the following discussion.

This is a quote from Alan-- "The lowest voltage to be encountered in an overhead transmission line is probably 1500 volts, and that's very low, and likely carrying a large current load. Typical local distribution is 12-24-36-69 kV, and the big grid distributions are 115, 230 and 500kV"

Notice below that he is now talking about "when you bite into a 115kV line"!!

He is now upping the ante to bluff. He now has me dealing with one of those big interstate lines that are on steel towers, when the OP and I were only talking about some line that fell from a wooden pole in front of the house. He is now not so sure that I couldn't deal with 12kV!!!! HA, HA, HA

Bullshit. There is a Neutral wire run along with the HV lines. The ground rods connected to the neutral are to reduce lightning damage. There were a few installs using the earth for a return, but they were not very efficient, and had crappy voltage regulation, not to mention they could kill you if you were barefoot and walked too close to the end of the line, where the return went to ground. Using the earth as a return conductor has been illegal for decades

As far as Transmitters, they use the earth as a counterpoise. A large metal plate that was not grounded would do the same thing, at hundreds of times the cost of an array of ground radials. Show me a TV transmitter that uses the earth for anything other than a place to bleed off electrostatic charges, and sometimes to divert direct lightning strikes to ground. Before you answer, I was a broadcast engineer at numerous AM radio and TV stations, starting in the mid '70s and I have even seen the 500 KW WLW 700 KHz AM transmitter in Mason Ohio.

More ignorance. By the time the voltage is high enough to notice, you may be dead. The city of Orlando lost several horses used by the police department to patrol certain areas. The both died a few weeks apart, within 50 feet of the same spot. They investigated the area and found that when a sign ahd been replaced, the installers cut the old underground cable and left it in place. Someone had turned the breaker back on, so there was a live 120 VAC between the end of the old cable, that slowly dropped to zero at the steel pole the new sign was on. The horses had crossed repeatedly across the edge, both when they stop and turned while in the affected area, they died.

--- What you don't seem to understand is that what usually kills you when you get electrocuted is that your heart gets confused about when it's supposed to beat and that bringing that confusion about doesn't take much current. Arguably 20mA through the heart is lethal, so if you picked up a 7500 volt line all that would be required to let that quantity of charge flow through your body would be a resistance of 375,000 ohms. That would be the resistance through the insulation of the conductor, your body, the soles of your shoes and, ultimately whatever else was between the soles of your shoes and the circuit neutral. Of course whether you picked it up with your right or left hand would matter, as would if you placed your other hand on the ground to steady yourself when you bent over to pick it up which, in your case, I assume you would.

---

--- No, it isn't.

---

--- It sounds to me like you're incapable of participating in a technical discussion intelligently, so what you do, instead, is grab your pud and pullet.

-- John Fields Professional Circuit Designer

Wow...what brilliance. If it looks safe on a graph in some book, then clearly it's safe in all possible conditions, because of course we all know that all real-world situations correspond exactly to those assumed in the book, always and forever. Ground is a perfectly uniform conductor, and would always be receiving current from the downed line at a single point of contact, etc., etc., etc..

Let us know where you want the body sent.

Bob M.

I am going nowhere near a hot high-voltage wire lying on the ground. I'm going to call 911 and let the pros handle it. Dirt conducts enough to run 50 mA through my heart, and that doesn't appeal to me. It doesn't conduct enough to drag a kilo-amp power feeder down to zero volts.

Serious earth grounds are big arrays of deeply driven metal posts or mesh, often seeded with conductive chemicals, and even that has a hard time getting below an ohm in some soils. A wire merely lying on the ground won't be "grounded" in any usable sense, namely it will be at practically 100% of its "up there" voltage (or even more, as JF notes.)

And I know damn well that earth is *never* used as a return for power transmission. That would be insane for any number of reasons. Look at some power poles sometimes; you'll see 2 wires, 3 wires, 4 wires, but nobody transmits power over one wire.

Really, the mathematics of this situation isn't complex. There is a wide range of numerical assumptions that suggest death. Just crank some numbers and see for yourself.

John

You may well feel nothing until the instant the soles of your shoes arc through, which you may or may not notice before you die.

If a person is walking into a large ground gradient unaware, at normal walking speed, he may well take a couple extra steps, or maybe fall over and touch with other body parts, before figuring out what's going on and reasoning out how to safely retreat. If he's walking into the gradient aware if its existance, he's an idiot, and we have a surplus of idiots, way more than we need.

"Leaving the area" implies a knowledge of the gradient map, and the intelligence and cool-headedness to take advantage of that knowledge.

John

Good point. Surface or subsurface features (rocks, pipes, clay, roots, wet/dry patches, cracks in the sidewalk) could produce a very fractured surface potential map, so the first step that produces any noticable shock is the one that's lethal.

John

Just FYI, downed lines are not a 911 type of problem. Getting electrocuted is, of course, but if you're just reporting a downed line, the right number to call is your local power company. If the line is on a public road, call the local police (their non-911 number).

All of your stories (especially the horse one) could warn anyone to never walk anywhere. All the things you mention COULD happen if I was to get unluckier than usual. But I will probably get hit on the head by a meteorite after getting mugged on my way to the scene anyway. So I'd better join the rest of you hiding under the bed with the bogeyman. OR, I could play the percentages, go with the generalized voltage gradient graph, and walk out in the backyard without worrying that I was going to step on a metallic ore outcropping that had gotten connected to a loose wire. WOW! ain't I BRAVE!

you