Electrical Safety Reminder

[Alpha_Geek]

This is why you don't screw with stuff you don't understand:

Warning, disturbing content involving human electrocution.

[yt]http://www.youtube.com/watch?v=bQVqze35fx0[/yt]

 

[Saturn0660]

Nice.. That dude is on Fire... I love it..

 

[judge alba]

shocking!

 

[Robert Maxwell]

Jesus Christ.

 

[Zachary Smith]

shocking!

What you mean is, "Shocking, Moneypenny! Absholutely shocking . . ."

 

[Joshua Howard]

Nice.. That dude is on Fire... I love it..

^ That is one - albiet kinda perverted - way to look at it. Movin' on...

Wow, he got toasted nice and crispy. I never realized that electric rail wires had enough electricity in them to leap that far though; it looks like over 2 feet of distance was between the dude and the wires.

In any case, a similar incident occured in my town a while back when a couple kids scaled the power line tower leading over the Tacoma Narrows. The second kid stopped climbing after the first one got roasted on the frame above him.

 

[Alpha_Geek]

Not sure if he made contact or not. It does look like he was grabbing for the wire to stabilize himself, though.

Indian rail voltages are 1500 VDC or 25 KVAC. Most of he system is 25KV.

Here's a 25 KV arc in an controlled environment. Current is less of a factor than voltage for arc distance.

[yt]http://www.youtube.com/watch?v=-phl5m9rUOs[/yt]

As you can see, the arc can only travel a centimeter or less at 25KV.

As for what happened to the unfortunate man in the OP, at 25 KV, about 250 amps of current was passing through the dude, as the human body has an electrical resistance of approximately 100 ohms. The rail system certainly can provide that much with no difficulty, as it provides enough current to push multipe trains loaded with frieght or passengers on the rail line.

 

[backstept]

owwww . . . .

 

[StarryEyed]

Alpha Geek, where do you get the 100 ohm figure? Human skin easily has a resistance of 100,000 ohms. I realize this goes out the window when arcing is involved but I'm still curious where you get your 100 ohm figure from.

Even if you are right about 100 ohms body resistance, he definitely did not have 250 amps go through him. That IS the figure you would calculate from Ohm's law. Twenty-five thousand volts divided by 100 ohms = exactly 250 amps - but that is assuming the power source could source that much current. That is very unlikely. Twenty-five KV x 250A = 6.25 megawatts or about 8333 horse power - way more power than the train would need. I would guess that actual current figure through the person's body (assuming 100 ohms body resistance) at more like 25 amps. That is about 7 times the current used in the barbaric electric chair - more than enough to fry a person very quickly.

 

[Alpha_Geek]

Starryeyed, the rail line has enough current to run multiple freight and passenger laiden trains concurrently. There's enough current to push multiple locomotives. If you wanna dance about how many watts equal a horsepower, and how many horsepower a locomotive employs, I'll go there with ya.

746 watts per horsepower.
This says most electric locomotives run 6 to 7 thousand horsepower.

6500*746=4849000 watts
4849000(watts)/25000(rail voltage in most of India)= 194 Amps needed per train on the line, ignoring line resistance over miles of line.

The circuit breakers never even noticed dude, or there wouldn't have been a second shock.

As for the skin resistance versus muscle and other resistance, the skin offers little to stop a 25KV potential from penetrating it.

I did miss a little. 100 ohms is across the chest cavity, and is the figure bandied about in safety briefings for every electronics class I've taken in civilian and military life. 500 ohms is a conservative value for limb to limb. 50 Amps at 25 KV still equals a death for putting your hand on an energized circuit..

 

[StarryEyed]

It looks like I underestimated how much power a train needs and I didn't consider multiple trains serviced by the same lines. I acknowledge your point that the circuit-breakers did not even trip at the first jolt which means source-current wasn't an issue.

I've never heard of human-body resistances at such high voltages which is why I was curious. Normally, high-voltage sources are so current-limited such as in a gasoline engine ignition systems or a CRT aquadag that they are way under the current capability to kill a person or they are high-power distribution lines with enough current to reduce a human to ashes. Either way, human-body resistance isn't very relevant.

The link you provided though says that 240 mA is the maximum to expect through a body at 120V. That equates to 500 ohms (as you said). That is at least five times the current needed to cause heart fibrillation. Most of the time, people are not killed by 120V shocks. I must therefor question your claim that the train-rider took 250A. Fifty amps at most, likely. Still enough to make a wreck of one's medical records!

Definitely a Darwin award. Any indication of who this person was or why he did what he did?

 

[Nerys Ghemor]

In India, wouldn't you be looking at more than a 120 V current? The US is on 110 V, but other countries are on 240. Wouldn't that make a difference, as to the severity of shock you receive, if you're ungrounded as it seems this guy was?

 

[Meredith]

In India, wouldn't you be looking at more than a 120 V current? The US is on 110 V, but other countries are on 240. Wouldn't that make a difference, as to the severity of shock you receive, if you're ungrounded as it seems this guy was?

Voltage don't kill it is Amps that does the frying!!

Regular static shocks from walking across carpet can be in the tens of thousands of volts but less than 1 milliampre.

Think of Voltage as Pressure and Amps as Flow.

A can of hair spray has a lot of pressure but it only releases a small amount of substance at a time. Compare to a fire house which is high pressure and high volume. Which one will knock you on your ass? It is a reasonable analogy.

 

[Alpha_Geek]

In India, wouldn't you be looking at more than a 120 V current? The US is on 110 V, but other countries are on 240. Wouldn't that make a difference, as to the severity of shock you receive, if you're ungrounded as it seems this guy was?

That's house current. Special applications, like trains, use different stuff. It's the same in industrial and commercial applications all over the world,

I looked up what voltage trains used before the first post. some train services in india use 1500 VDC, but that's being phased out in favor of the far more prevalent 25 KV service.

Dude was grounded. If you have a metal box that runs on electricity with people in it, you ground the box so that if the feed line drops, the box doesn't go hot. Even if the guy was barefoot, the half inch aroun the shoes to ground is a small feat (pun damn well intended) for 25000 volts to jump.

 

[Alpha_Geek]

Voltage don't kill it is Amps that does the frying!!

Regular static shocks from walking across carpet can be in the tens of thousands of volts but less than 1 milliampre.

Think of Voltage as Pressure and Amps as Flow.

A can of hair spray has a lot of pressure but it only releases a small amount of substance at a time. Compare to a fire house which is high pressure and high volume. Which one will knock you on your ass? It is a reasonable analogy.

Correct. The current was limited by the electrical resistance of the body. In this case, the current available far exceeded the ability of the conductor...err.. I mean passenger conducting... ummm.. unfortunate victim to conduct it. This is diffeent from carpet shocks, where the voltage is aplenty, but the current available is nigh unto infinitely smaller.

 

[Trekker4747]

This is why you don't screw with stuff you don't understand:

Warning, disturbing content involving human electrocution.

[yt]http://www.youtube.com/watch?v=bQVqze35fx0[/yt]

Frankly, I think the ending to Slumdog Millionaire they went with is better.

 

[John Picard]

220...221 -- Whatever it takes.

 

[Supreme Admiral]

(Double face palm)

Stupid.

 

[Alpha_Geek]

...Still enough to make a wreck of one's medical records!

Definitely a Darwin award. Any indication of who this person was or why he did what he did?

End of the line, to be certain!
I've looked around and not seen much detail about who the ex conductor (electrical, not train) was. Some of the googlage indicates he may have been mentally disturbed, yet I have seen plenty of video of Indian commuter trains with people hanging out doors, sitting on the roof, etc.

Watching the video, it appears to my keenly amateur sense of observation that the dude was walking on the rounded surface of the roof and was merely reaching for the line as a method of increasing his stability. If it was a deliberate thing, I would think he would have stopped walking before reaching up instead of continuing his pace.

 

[Brent]

Why was he up there in the first place?