ELECTROCUTION: how to avoid

[pdqdl]

Certainly. They rate the fence chargers in Joules (very capably explained above). They cite little bitty numbers that would never even run a flashlight.

If, however, you were unfortunate enough to get your tongue stuck on a 10Kv fence charger, you might just wish for enough amps to put you out of your misery!

 

[EdenT]

I touched an electric fence once....

I was just telling my friends how it felt like there were little bumps running along the wire under my fingers. Next moment - BANG - I'm on the ground with sore kidneys and my friends are laughing hysterically.

Never felt the urge to repeat the experiment!

Thanks for the post PDQ. A good wake up and reminder call for us all.

 

[gwiley]

It takes surprisingly little voltage/current to kill you provided it takes the right path. One of the quickest ways to end your misery is to ground a power source through your chest by grabbing it with one hand and a good ground with the other.

As little as 60mA can kill you if it hits the heart muscle.

 

[BlueRidgeMark]

4kv is quite common, in old line I believe. Fence charger voltage is not the same as primary voltage, can't be, well, maybe the voltage, but primary has amps. 4kv will kill you, 10kv from a fence will not, see what I am getting at?

Voltage is voltage, amps is amps. You can have very high voltage with very low amperage. If you touch a doorknob and get a shock, you just experienced something in the neighborhood of a 35-100 kV zap.

Yep, you heard me right. A static shock you can feel is around 35,000 volts on the low end. The really nasty ones get up into the 100k range.

Amps? Probably picoamps, MAYBE microamps.

A spark plug runs in the 40,000 to 50,000 volt range.


On the other hand, you can also have very high amperage with low voltage.

12v can kill you very dead under the right conditions. A car battery can supply lots of amps! A 24v starting system packs quite a wallop in amps.

 

[pdqdl]

... If you touch a doorknob and get a shock, you just experienced something in the neighborhood of a 35-100 kV zap.

Yep, you heard me right. A static shock you can feel is around 35,000 volts on the low end. The really nasty ones get up into the 100k range.

Amps? Probably picoamps, MAYBE microamps.

Wikipedia disagrees slightly: http://en.wikipedia.org/wiki/Static_electricity

"The capacitance of human body can be as high as 400 picofarads (though typically ranging between 100 and 300 pF); a charge of 50,000 volts, discharged e.g. during touching a charged car, creates a spark with energy of 500 millijoules.[19] The maximum potential is limited to about 35–40 kV, due to corona discharge dissipating the charge at higher potentials. "

So not as high as 100Kv, but plenty enough Kv to get your attention.

This article goes into the physics of static charges, particularly related to fuels and ignition. It is well worth reading if you deal with gasoline and it's tendency to ignite with a spark.

A curious observation that I made while reading: The minimum static discharge that a human is able to detect is slightly lower than the minimum spark required to ignite most petroleum products. So we seem to have engineered a system that we can safely detect without any additional test equipment!

 

[BlueRidgeMark]

Wikipedia disagrees slightly:

Wikipedia is worthless, at best. At worst, it misleads.


I have seen the 35-40 kV claim in a number of places, but other sources say it can go as high as 90-100 kV. So, there is disagreement in the literature.

 

[clearance]

We are talking about powerlines here, I believe. Primary lines, that being the bare ones, at the top on power poles, either one or three of them, are freaking deadly. If they have enough power to light up many homes, they will kill you. Enough of this high voltage with no amps, 4 kv won't get you if you pizz on it stuff.

I was trained, by linemen, so I know the deal, stay the f-back, shuffle or hop, all that jazz, barricade the area and call the power company. dukntz made a pretty good post here, read it.

 

[dukntz]

Ok, if you guys are some smart, Lets see who can answer this question correctly. You are sitting in your car at a stop light and someone slides into a power pole and live 7200 volt line comes down, landing on your car. What happens to you in the vehicle?

 

[clearance]

Ok, if you guys are some smart, Lets see who can answer this question correctly. You are sitting in your car at a stop light and someone slides into a power pole and live 7200 volt line comes down, landing on your car. What happens to you in the vehicle?

You are energized at around 7200 volts. Stay in your car!

 

[Pierreg]

Electrocution

Hello,Working for a power company,I have seen many things over the yeaohrsSafety first.My hat's off to all the tree trimmers and line workers.Electrical accidents are almost always fatal.Please know that almost all transmission&distribution is in a two auto reclose arrangement going to lockout on the third try.The system is designed to protect itself and have the least amount of outage time.Always consider any line live and deadly.Our Linemen in the US are the cream of the cream.I recall a 6mile convoy going south after Katrina.Working with completely destroyed lines.Please be safe,call the power company to D/C any overhead lines(distribution)and do your work safely.We all need to look out for each other.Be safe gents......

 

[pdqdl]

Ok, if you guys are some smart, Lets see who can answer this question correctly. You are sitting in your car at a stop light and someone slides into a power pole and live 7200 volt line comes down, landing on your car. What happens to you in the vehicle?

If the wire remains ungrounded except for your car...your tires eventually catch on fire...the fire spreads...you grab the door handle because getting electrocuted isn't quite as certain as burning to death...and if you are lucky you leap out of the car, landing on both feet.

Hopping away from the car, you have little exposure to the step potential (pretty small on a 7Kv line) and you begin to bang on the door of the offending car that nearly killed you.

...the offending driver doesn't have insurance...your car is destroyed. A fight breaks out...you go to jail for choking the life out of some negligent motorist that richly deserved it!


One of my customers told me a similar tale of his dump truck being pushed into a much bigger primary by an asphalt paver while the bed was up. That is what happened to him, except the choking and going to jail part. And yes, he did do the jump and hop routine, very much to his survival. He is driving around in his shiny new truck, too.

 

[BlueRidgeMark]

Ok, if you guys are some smart, Lets see who can answer this question correctly. You are sitting in your car at a stop light and someone slides into a power pole and live 7200 volt line comes down, landing on your car. What happens to you in the vehicle?

Nothing. You are in a Faraday cage.



As long as your tires don't catch on fire, anyway!

 

[ropensaddle]

Ok, if you guys are some smart, Lets see who can answer this question correctly. You are sitting in your car at a stop light and someone slides into a power pole and live 7200 volt line comes down, landing on your car. What happens to you in the vehicle?

I get a dip and wait for the troups as long as fire does not break out. If fire breaks out oh well I will take my chances. Now another scenario you are trimming tandem down a powerline meaning your in one tree and your buddy is in the next and you are way out in the sticks. He bridges the gap and is being electrocuted you can't reach him with your insulated pruner and you look down and no one is anywhere near the lines. What would you do?

 

[clearance]

I get a dip and wait for the troups as long as fire does not break out. If fire breaks out oh well I will take my chances. Now another scenario you are trimming tandem down a powerline meaning your in one tree and your buddy is in the next and you are way out in the sticks. He bridges the gap and is being electrocuted you can't reach him with your insulated pruner and you look down and no one is anywhere near the lines. What would you do?

Fall a big top onto the line, making real sure it broke free (shallow undercut). Hopefully it would rip the line down and help, maybe not, but I would try it. Even better to fall a big tree on the line. They teach you not to do this, but so what, they gonna put you in jail for trying?

 

[ropensaddle]

Fall a big top onto the line, making real sure it broke free (shallow undercut). Hopefully it would rip the line down and help, maybe not, but I would try it. Even better to fall a big tree on the line. They teach you not to do this, but so what, they gonna put you in jail for trying?

That may be one way. I will see if anyone else chimes in before telling what I would do.

 

[EdenT]

I liked clearance's solution but....

You could throw a piece of metal (your saw or pole belt) (make sure your not connected to it) across all the lines creating a total short which will hopefully cause the isolation fuses to trip. Oh yeah, duck!

or

If you were more mercenary, you could get on the phone and take out a very large life insurance policy on your buddy with you as the sole beneficiary!

 

[BlueRidgeMark]

If you were more mercenary, you could get on the phone and take out a very large life insurance policy on your buddy with you as the sole beneficiary!

Man, that's cold!



Funny, but cold! :hmm3grin2orange:

 

[ropensaddle]

Lol no I would put my pruner on the primary and either push or pull it clear of him or cut it! Only with an insulated pruner though.

 

[Pierreg]

Plan his Funeral&Write a nice obit.....

And please bury him with his best saw....be thankful it wasn't you.Sorry for the lack of humor.Working in the power gen.industry and around high pressure steam equip,I tend to get a bit intolerant of foolish mistakes.

 

[pdqdl]

Just refreshing this thread...a reminder!

I like to wake this thread up every so often.

Until I recently was made aware of the danger of just walking through a high voltage field, I was likely to get zapped. If you do tree work (or any other work) around power lines and you haven't followed this thread before, you should take the time to read the beginning of this thread.

I suppose that walking into a strong EMF field would be less risky than walking away. Presumably, you would feel the voltage growing before you managed to kill yourself.