Very true. Does anyone know the current of the live rail or wot?nino_savatte said:Remember it isn't the voltage that kills it's the amperage.
Is the live rail dangerous?
- Thread starter beeboo
- Start date
T & P
|-o-| (-o-) |-o-|
It must still be a dangerous current/amperage because people have been regularly been reported as dying after coming into contact with it.
Children in particular are often reported as victims as they played around the tracks or crossed them... perhaps the current is strong enough to kill kids but a fit adult might have chance of surviving? Either way I wouldn't fancy to put it to the test...
Children in particular are often reported as victims as they played around the tracks or crossed them... perhaps the current is strong enough to kill kids but a fit adult might have chance of surviving? Either way I wouldn't fancy to put it to the test...
munkeeunit
sumptuous lushness
I wouldn't advise urinating on the live rail.
Pretty embarassing way to die, and if you're really unlucky it'll be classed as suicide by urination.
Grim.
Pretty embarassing way to die, and if you're really unlucky it'll be classed as suicide by urination.
Grim.
pembrokestephen
New Member
This whole "it's the amperage that kills" bullshit is pointless.5T3R30TYP3 said:
But, to answer your point -
When they started running the Eurostar trains into/out of Waterloo, they had problems with them because the amount of current they try to draw when running on the 3rd rail was too high, and the short-circuit protection was tripping at the distribution stations. As far as I remember, that tripping occurred at around 5,400A (yes, FIVE THOUSAND FOUR HUNDRED).
nino_savatte
No pasaran!
pembrokestephen said:
Why? It is the current that kills...I do remember something from school physics you know.
Locally there is a DC overground train that runs into London. Some years ago a group of boys tried to cross the line at a place where the fence was down. One of them didn't make it. He was wearing a long coat and it was raining. The wet coat trailed on to the live rail and he was killed.
Consider yourself lucky that you are still alive. If that platform is slippery other than as a one-off caused by spillage then the rail company needs to be taken to task.
H
Consider yourself lucky that you are still alive. If that platform is slippery other than as a one-off caused by spillage then the rail company needs to be taken to task.
H
pembrokestephen
New Member
It's a dangerous VOLTAGE.T & P said:
Any adult coming into direct contact with the live rail would be very lucky to come away without serious injury.
(from http://www.tlc-direct.co.uk/Book/3.4.2.htm)
For direct current (it sez here), a current flow of 200-500mA is enough to cause death by ventricular fibrillation. Given a worst-case resistance of 500 ohms (the majority of the human body's resistance is in the skin, but damaged - eg burned - or damp skin will lower the resistance dramatically), that current would flow at a voltage of 250V (by Ohm's Law).
Practically speaking, human body resistance is likely to be much higher, so there's a good chance that ventricular fibrillation might not occur, especially if there wasn't a direct path to ground (eg. one hand on live, the other on a running rail, ie. earth). However, there is another problem, too: there's a thing called "let go" current - when an electric charge passes through muscles, it can cause them to spasm, which means that the person is unable to detach themselves from the supply. For DC, as used on third rail traction supplies, the "let go" current is about 75mA for an average man, so if we assume a resistance (ie not a worst-case one) of 1.5kilohm, that current would flow at a voltage of about 100V - well under the 600-750V of the traction supply.
The other major risk with high-voltage DC supplies is deep tissue burns - ie, heating of the internal parts of the body as a result of the current flowing through them. DC traction supplies are more than capable of supplying a high enough voltage to ensure that current sufficient to cause these burns would flow, and, coupled with the "let go" problem above, this means that someone who made good electrical contact with the live rail would be very likely indeed to end up with such burns unless he were removed very quickly indeed.
pembrokestephen
New Member
That's as may be, but the current that flows is dependent on two things: resistance and voltage. Notwithstanding the fact that Ohm's Law is generally stated as V = IR, it's almost invariably the case that I is the variable factor, while V and R are generally givens. That's to say: the current that will flow is proportional to the voltage across the circuit, and inversely proportional to the resistance through which it is flowing.nino_savatte said:Why? It is the current that kills...I do remember something from school physics you know.
Where people sometimes get confused is where they're dealing with a power supply with an effectively high internal resistance: for example, if you were to touch the HT terminal of your television tube (typically running at about 25kV), you'd get a very nasty belt, and - if you have heart trouble - potentially it MIGHT kill you, but try the same thing on the 25kV overhead traction current on the railway and you'll *smoke*. This is because the TV CRT power supply is only capable of delivering a few milliamps at that voltage, so your resistance would cause the effective voltage being supplied to you to drop very sharply, while the traction current supply is potentially capable of delivering around 1-200A, and the voltage drop due to your connecting yourself across it would be negligible.
Not sure how much this guy knows his stuff, but the general opinions I've see do veer towards 'it's combination / situation' based.
http://www.dribin.org/dave/blog/archives/2003/12/29/amps_vs_volts/
Either way, I'll be damned if i'm going to experiment to find out the true answer
http://www.dribin.org/dave/blog/archives/2003/12/29/amps_vs_volts/
Either way, I'll be damned if i'm going to experiment to find out the true answer
pembrokestephen
New Member
I think it points out how dangerous a slippery platform can be - actually, I think you're lucky simply not to have had a more serious physical injury, quite apart from the risk of electrocution!beeboo said:Nasty! I'll stop moaning about my bruised knees now (maybe)
I go with editor's view, though, that suing them for this kind of thing is not the answer...
pembrokestephen said:
Luckily I pretty much landed on my feet first, rather than going over head first which would have been much worse.
If it hadn't have been for the other passengers trying to manhandle me back up onto the platform, I wouldn't have been injured at all! Perhaps it is them I should be suing?
I think it was a bit of a freak accident really, although I am kind of surprised that this type of thing doesn't happen more often.
munkeeunit said:
It would be like a little fuse burning out.
_angel_
.
I'm quite shocked (pardon the pun) that a platform could be so slippy as to make you fall off it! It doesn't bear thinking about really if there'd been a train coming. 
Surely a poor choice of tiling/ paving materials is at work there and someone should be made aware of it: complain.
All the same to land on the live rail I think you'd have to do more of a long jump than a slip-up.
Surely a poor choice of tiling/ paving materials is at work there and someone should be made aware of it: complain.
All the same to land on the live rail I think you'd have to do more of a long jump than a slip-up.
Maddalene said:
For some reason, as soon as the government gave BR the money to do up stations ready for privatisation, they started covering every available flat surface with these terazzo-like stone-in-shiny-cement tiles.
In winter, the concourse at Liverpool Street is like an ice-rink. If you don't slip and break an elbow in a free bit of space, you'll trip over one of the yellow plastic warning pyramids put there as evidence for the court case.
Bring back tarmac platforms!
pembrokestephen
New Member
The bumpy stuff is to tell blind people it's there: it's the same bumpy stuff you get at pedestrian crossings.Maddalene said:Did they? I'm sure close to the platform edge at Leeds there is some kind of bumpy stuff going on (a bit like you get at crossings) to prevent ice forming (I assume). I could be hallucinating tho.
Woe betide the blind person who mistakes a platform edge for a pedestrian crossing, though
, although I expect that the presence of trains and platform announcements is probably a bit of a giveaway.
Tom A
Goat among sheep
My A-level physics teacher said that AC was less dangerous than DC due to the nature of AC means that the victim might be 'catapulted' away from the source of the current while DC doesn't have this property, so exceeding the 'let go' current means that he is stuck until some external force pushes him/her away from the source, or until he fries.
Lovely....
Lovely....
I vaguely remember someone posting on another thread that firefighters searching in dark rooms are trained to use the backs of their hands - or hold their hands out backwards if you prefer - so that if they do come across a live wire the shock will make their fingers curl up away from the wire.
Not much help if you're sliding arse over tit toward 650V DC
Not much help if you're sliding arse over tit toward 650V DC
pembrokestephen
New Member
The "let go" current still exists for AC, but is MUCH higher. There's a fairly long'n'winding post of mine up there ---^ on the thread somewhere which roughly paraphrases various sources on the subject...Tom A said:
Maddalene said:I'm quite shocked (pardon the pun) that a platform could be so slippy as to make you fall off it! It doesn't bear thinking about really if there'd been a train coming.
Surely a poor choice of tiling/ paving materials is at work there and someone should be made aware of it: complain.
All the same to land on the live rail I think you'd have to do more of a long jump than a slip-up.
Yep it was those shiny tiles that laptop was talking about - they don't go right up to the platform edge, but even though I was behind the yellow line, I had enough momentum when I tripped to carry me right over the edge.
I landed slap-bang in the middle of the tracks - if I'd fallen over forward when I landed (which nearly happened - stumbled forward instead), I'd have hit the rails (normal and live) on the other side, for definite.
Fingers said:can anyone tell me why foxes, cats and stuff do not get electrocuted by the live rail? always wondered that
darwinism?
nino_savatte
No pasaran!
Fingers said:can anyone tell me why foxes, cats and stuff do not get electrocuted by the live rail? always wondered that
I've seen pigeons stand on the live rail and not get fried. There's no justice in this world, I tell ya!
Fingers said:can anyone tell me why foxes, cats and stuff do not get electrocuted by the live rail? always wondered that
Standing on the live rail is not a problem do not try this however
A fox that tried to do a Monarch of the Glen pose with hind legs on the running rail and forelegs on the live rail, however, would explode.
Tom A
Goat among sheep
Nice...laptop said:
It's due to just standing on the live rail alone, and not touching the ground and connecting it to earth, so the animal isn't making an electrical circuit. It's also the reason why pigeons don't get electrocuted when they perch on electrical distrubiton wires, which can be up to 132kV.
Apparently, according to my dad, when they first put up overhead wires out of Euston they were plagued by unexplained wire breakages.
It took them a while to work out what was going on. Then a pattern started to emerge.
The breakages always happened at the mouths of bridges or tunnels. They always happened when it was raining.
So the next time it happened, some engineers went to have a closer look.
They found a few singed feathers.
They worked out that owls were landing on the live wires and perching on them - as noted, no circuit, no problem.
Then the owls would shuffle along the wire under the bridge and out of the rain... stretch with a sigh of relief... touch the bridge... and bang!
E2A: I suggest that the reason you don't see the bodies of small creatures that have completed the circuit is that there is very little left.
It took them a while to work out what was going on. Then a pattern started to emerge.
The breakages always happened at the mouths of bridges or tunnels. They always happened when it was raining.
So the next time it happened, some engineers went to have a closer look.
They found a few singed feathers.
They worked out that owls were landing on the live wires and perching on them - as noted, no circuit, no problem.
Then the owls would shuffle along the wire under the bridge and out of the rain... stretch with a sigh of relief... touch the bridge... and bang!
E2A: I suggest that the reason you don't see the bodies of small creatures that have completed the circuit is that there is very little left.
ATOMIC SUPLEX
Member Since: 1985 Post Count: 3
Science is interesting
pembrokestephen
New Member
Not a lot of people know this, but while foxes and most sensible animals tend to go OVER obstacles, badgers try to go UNDER them.laptop said:
Coupled with the badger's obstinate tendency not to change its route in the face of any new obstruction, the badger population in Dorset faced a certain amount of additional challenge when they electrified the line from Bournemouth through to Weymouth. It went something like this:
*badger approaches slightly-higher-than-running-rails 3rd rail*
"Derr, woss dis, then? Hmm"
*puts snout under live rail*
*shoves up HARD*
BANG!
Goodbye, Vienna (look, the badger was called Vienna, OK? No, I don't know why)
In the end, they solved the problem by putting in gaps in the live rails at known badger crossing points.
Little known fact, that.
