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Why NOT to touch power lines.

Discussion in 'Electrical Engineering' started by Rich., Jun 8, 2009.

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  1. We used to cook hot dogs that way back when AC power was cheap.

    Also, he would have had a problem even with a lower voltage. The only
    reason one can call it high voltage is because the electrical power
    industry (err... the NEC) has defined "high voltage" as starting at like
    600 Volts. Other standards place it at 1000 Volts.

    That train was likely fed by a 400 Volt line. Not high voltage, but
    you can bet that the "resistor" that a person poses to that line to
    ground isn't high enough to keep the person from frying like a 1973 hot
    dog in a tray on pins plugged into the wall.

    Not high voltage. Certainly high enough though. The idiot was free from
    it, and he touched it a second time.

    Reminds me of Dilbert's manager.
     
  2. I doubt that would only be 400v, much more likely 4digit power.

    Rheilly P
     
  3. The trolley and the other electric trains in the US are at 400V to my
    knowledge.

    Keeping arcing down is one reason. Watts are watts. The motors do not
    need "4digit power". It is far safer that way, especially in wet areas.
    The lines are not that far above the trains. Sheesh. The trains are
    made by Siemens.

    The train in the picture in India must be a local, 1.5kV DC. There was
    one arc, then a body roast arc, then a body roast fire. He was dead
    faster than any electric chair ever made.

    That was not your little 1.5 kV photo flash source, which makes a snap
    as it sends a single 1/10 second arc through you, if that.

    That was POWER behind that 1.5kV. It remained at 1.5kV, and was a very
    low value resistor for a few seconds.

    Unbelievable! I am surprised that a broadcast or cable news service
    didn't pick it up. (not the video, the mention of it).
     
  4. Note that the person was very much so being cooked. One could see the
    arc through his entire body.
    A 20kV or even a 400kV power supply for a friggin transmitter has no
    balls whatsoever compared to a high amperage DC feed for powering a
    train.

    Most DC supplies are current limited against dead shorts as well.

    A DC fed train gets orders of magnitude more available current AT
    voltage than a simple supply for a transmitter is capable of providing.
     
  5. Mostly, India is same as UK, i.e. 25kV on overhead rail pantographs.
     
  6. If you are stupid enough to believe Edison's bullshit, you are more
    ignorant of history than I thought. DC most certainly can kill, and it
    ALSO can kill by way of causing a defibrillation of the heart. DC deaths
    are not all attributable to the frying of flesh.

    It is less likely, but absolutely possible to get a fibrillation event
    from DC..
    I can take two #16 bare solid wires at six inch strip, and grab the
    bare ends while the other ends are plugged in. I can crawl up the wires
    with my hands until the curl in my wrists can no longer take it.

    Most deaths from such a low voltage are due to the element of fear.

    If I am working on a chassis, and that same 120 VAC hits me
    unknowingly, it will knock me across the room.

    If I know it is there, I can touch it. I would not dare do this,
    however, with 240 or a higher than 120 Volt source.


    No let go current is rather
     

  7. India's long inter-city runs are 25kV AC.

    Their local runs are 1.5kV DC.

    That guy got hit with DC from what I could see.
     
  8. Don Kelly

    Don Kelly Guest

    Hard to tell.
    I suspect AC- there were two distinct jolts with no arcing between and no
    follow up arcing after the second jolt -when his hand was still near the
    line- this is indicative of AC rather than DC. I also suspect that the
    line was cleared by a recloser and then re-energized, cleared again and
    locked out. Again, more typically AC practice. He deliberately touched the
    line once- he was dead before the second touch or near touch. I also
    suspect 25KV as most lines outside the Mumbai area appear to be 25KV AC -
    and one source indicated that this was supposed to be converted by 2002.

    Don Kelly

    remove the x to reply
     
  9. That is silly. The time gap was huge. Several hundredths of seconds
    easily. I saw two distinct pops. an AC "flash" is usually blue, and the
    AC cycles are the reason. The DC POP arc is usually the same color as
    what it practically instantly vaporizes at the entry/exit site. AC also
    causes reverberatory spasm responses. He stood there while the current
    fried the resistor.
    I doubt that seriously, considering the instantaneous currents required
    by trains on the track. It was far more able to completely fry him and
    not even wince at the loading.
    It isn't a sub-station service feed.
    But that is not what happened.
    It was 1.5kV DC. If it was their 25kV line, it would have arced to him
    before he even got to it, and would have continued to arc as he pulled
    away. It was clearly DC, and it was clearly low enough voltage that the
    arc remained below a couple inches, as the video demonstrates to the
    trained eye. Had it been AC, he would have had an arc as he pulled away
    the first time.

    Again, there will be no breakers opening with a load as "small" as a
    human on this type of feed. His entire incident used far less juice than
    a train does as it pulls out from a platform. And the immediacy of the
    event wouldn't "trip" anything either. A person on the wire will get
    continuously fried. A BAR across the feed *would* trip an interruptor.

    That guy fried so fast, the power source thought an engineer farted.
    Nothing more. A train represents a far lower resistance load. The "slew
    rate" by which his "event" made the current go up likely wouldn't cause
    more than a yawn, much less a trip.

    As I stated before, I read the discussions, and it was stated earlier
    by a guy claiming to be there (India, not the station) that they use 25kV
    for the long inter-city runs, and 1.5kV for the short run trains, which
    is a different rail system. Not interconnected. Replacing all those
    trains would be quite expensive.

    I think it was the DC set from the video. Ac would have arced to him
    before he got to it. Also, a big platform, there would have been no way
    they would have let him up onto the train. In the smaller system, it
    would be easier.

    It is just conjecture by both of us though. We both observed the same
    thing, and have both described plausible event chain theories.

    We should ask the "slumdog up in smoke" if such excitement leads to
    orgasm. We could ask David too. Oh, wait a minute! It's too late to
    ask either one! :) Now, we'll never know.
     
  10. Rich.

    Rich. Guest


    You remember correctly, it was the Presto Hot Dogger.
    http://www.gpopc.com/catalog/item/5313687/5766786.htm
     
  11. Please REFRAIN from top posting in Usenet. This is not your email
    client.

    They obviously waited until he was no longer burning, or they dowsed
    him, and then pulled him down. Very unlikely that they moved the train
    with him up there. The train was likely already dormant as a result of
    his presence.
     
  12. Yep. We had one, and one of my mom and dad's friends had one.

    They had a lid that actuated an interlock switch.

    I always thought they were a little exposed, but defeating the interlock
    was not easy to do. IIRC, it was pre-polarized plug days, ala early to
    mid seventies.
     
  13. Bwuahahahaha!I thought it looked a bit high.

    hahahaha! It would yield a readings it is conducting and exhibiting a
    field.
     
  14. So what? There are other posts of it elsewhere that have folks that are
    from India discussing it. They refer to two different systems being in
    use.
    None of it is at 26kV.
    I heard no buzz at all, and I had one where all the platform folks'
    dialogs were clear. I heard a pop. No buzzing or humming.
     

  15. The hall of souls was glad to have it back, since it appeared that he
    didn't want it any more.
     
  16. Don Kelly

    Don Kelly Guest

    ------
    Several hundreths of seconds or possibly 30-60 cycles. no big deal. Colour
    of arc depends on the material and temperature involved. AC flashes, even
    at light current are not necessarily blue- I have seen many that aren't.
    Streamer flashover as an insulator starts to break down is generally
    bluish but once a solid arc is established, it is yellow. Blue for
    ionization but yellow for follow current in a plasma.
    Reverbatory spasm results-why? 100-120Hz pulses- the body won't spasm at
    that rate-particularly above "let-go" .
    -------------
    ----------
    Possibly -it was a conjecture- neither of us know. However, I have known of
    a case where a person in contact with a line did cause tripping and repeated
    reclosure. He ended up on the ground with the wire on top of him (7200V) The
    interval between reclosures was longer and the current was not enough to
    kill him or render him unconcious but did do terrible damage. Rubber boots
    burnt through at the ankles, holes in his back -he lived as a basket case.
    All due to a combination of drunken bravado and stupidity.
    The reclosure conjecture came about from the dead time betweeen pops.
    -----
    -------
    True but this doesn't mean that some kind of recloser system isn't in use.
    Again no information
    ------------------------
    -------
    His hand was not far enough away between the pops for a 1.5KV arc to
    extinguish. I have pulled arcs of 1/2 to 1 inch at 5-10A at 120V. where AC
    simply produces a minor spark at the same voltage and current. The current
    would have been far less than that but DC arcs are recalcritant . Yes, 25KV
    would have arced to him but it is not possible to see if there was a pre-arc
    but it was possible to see that it was out momentarily
    ---------------
    ----------
    Actually, I can't argue with that - which then points to AC.
    -----------
    -------
    And the last of the 1.5KV DC was supposed to be phased out about 7 years
    ago.
    ----------------
    ------------
    Questionable - the video doesn't give the detail well enough to say. As for
    a big platform - please note the station building in the background
    Agreed- we don't have any information as to where and when, nor, in
    particular the actual voltage involved.
    So we can both conjecture and blow smoke.
     
  17. Don Kelly

    Don Kelly Guest

    A favourite demonstration by the local utility consisted of grounding
    (through a limiting resistor) one end of a hot dog on a "hot stick" and
    touching a 2300V line with the other end. "See, Kids, don't go after your
    kites- call us"
     
  18. Mahananda Express at Etawah in Uttar Pradesh, May 29, 2009 (or
    maybe a day or two beforehand - that might be the reporting date).
     
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