Page 1 of 3 123 LastLast
Results 1 to 25 of 71

Thread: Electrocution - how does it work?

  1. #1
    Join Date
    Oct 2019
    Posts
    9
    Post Thanks / Like

    Electrocution - how does it work?

    This is my first post, I hope its okay to start a thread on this. I did search but only found tidbits of relevant stuff in threads more focused on how not to get electrocuted while welding. My curiosity and theme of this thread is about electrocution in general, even outside of welding.

    My confusion on this began a year ago when I did a level 1 (3 total levels in the UK) electrical installation course. The instructor told us a current of 200milliamps is lethal. This (excuse the pun) was a shock, and I still do not understand it. Arent typical cellphone chargers these days at least 2000milliamps?

    Googling around I found this information about electrocution from a reputable source (ohio college)
    https://www.asc.ohio-state.edu/physi...l_current.html

    Which echoes the same sort of thing the tutor told us but in more detail;

    For currents above 10 milliamps, muscular contractions are so strong that the victim cannot let go of the wire that is shocking him. At values as low as 20 milliamps, breathing becomes labored, finally ceasing completely even at values below 75 milliamps.
    Apparently you stop breathing at 75milliamps

    As the current approaches 100 milliamps, ventricular fibrillation of the heart occurs - an uncoordinated twitching of the walls of the heart's ventricles which results in death.
    Your heart stops beating at 100milliamps, from which point you are both dead and severely burnt.


    This is a major puzzler..!

    I was thinking that maybe just maybe, DC is just magnitudes safer than AC. But according to this the difference is minor:

    https://www.brighthubengineering.com...ck-comparison/

    either AC or DC currents can cause fibrillation of the heart at high enough levels. This typically takes place at 30 mA of AC (rms, 60 Hz) or 300 – 500 mA of DC.
    It is the magnitude of current and the time duration that produces effect. That means a low value current for a long duration can also be fatal. The safe current/time limit for a victim to survive at 500mA is 0.2 seconds and at 50 mA is 2 seconds.
    Fibrillation of the heart with 300milliamps of DC? and supposedly fatal in about a second?

    I would feel pretty confident about sticking my phone charger in a sweaty armpit and not being electrocuted.

    In terms of welding, I am to understand both Americans and Europeans tend to use 230v welding machines as a baseline. The more robust industrial machines use 400v+ 3 phase , and we have one of those in the workshop of the welding school I currently attend. We were allowed to use to 400v machine from the first day if we desired. The machine I have been training on is a 1940's stick machine which has bare cable terminals connecting it to the 230v AC wall outlet. The terminals are very close together and it could easily be shorted by something metal falling on it or struck by a live welding electrode in the small space of the work booth. But it is not something we even get a warning about unless we ask.

    On stick machines in general, the electrodes are changed extremely frequently without turning the machine off. Our tutor never wears gloves even so does this bare handed. I can imagine personally easily sweating through a pair of leather gauntlets if working in the sun. It must be very very easy to get shocks during in multiple ways, and in fact our course booklet even told us to expect that!

    Why is the typical 160amps or so used in basic welding not harfmul when supposedly less 0.1 amps is lethal?

    Also in general welding, we hold workpieces in our hands while tacking. (Barehanded for some people) and we do not get shocks. The tutor told us that the current all travels to the return cable and would have no reason to go into our bodies. But by that logic we can work on rewiring live circuits in electrical installation, bare handed. As long as no circuits are broken it should be impossible to get shocked? because our bodies will never be the sole "completing element" of the circuit?

    (if anyone is wondering why I don't get the tutor to explain, the class is one evening session per week so very limited time that is best spent on actual welding)

  2. Likes RoadTrip liked this post
  3. #2
    Join Date
    Nov 2012
    Location
    new york city
    Posts
    6,987
    Post Thanks / Like

    Re: Electrocution - how does it work?

    to avoid electrocution always make sure the machine is grounded properly.
    i.u.o.e. # 15
    queens, ny and sunny fla

  4. #3
    Join Date
    Apr 2017
    Location
    Long Island, NY
    Posts
    345
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Electricity has to travel through your heart to kill you. As in from one hand to the other. Usually when someone gets shocked it's from a hand to a foot.

    When I was a kid an old timer told me that it's smart to keep one hand in your pocket when poking around electrical connections.

    And dc is more dangerous than ac because it grabs you vs throwing you.

    Ever notice birds sitting on high voltage power lines with no issues? That's because they're not grounded.
    Lincoln Invertec V205-T Tig/stick
    Miller Coolmate 1.3 Coolant System
    Millermatic 211 Mig Welder
    Speedglas Adflo PAPR 9100 FX-Air
    CertiFlat FB2430 fabBlock U-Weld Kit Welding Table
    FW3012 CertiFlat fabWing 30" X 12" Extension Table

  5. #4
    Join Date
    Oct 2019
    Posts
    9
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Quote Originally Posted by henry42 View Post
    Ever notice birds sitting on high voltage power lines with no issues? That's because they're not grounded.
    The thought about grounding already came to mind and I tried to get tutor to explain it but I didn't manage to get a thorough enough explanation to understand. He said something along the lines of it not making any difference at all whether a person welding was grounded or not. That the electricity only wants to travel between the two welding cables and no where else. That it would not decide to take a short cut to ground through our bodies because it has no inclination to go to ground, that it goes to the other terminal.

    We all know that in warm & poor countries, the kind of people who weld rarely even own a pair of shoes. And they definitely do not wear gloves. If the current had any tendency to go to ground, surely the operator would be getting electrocuted on a daily basis?

  6. #5
    Join Date
    May 2010
    Location
    ct.
    Posts
    1,257
    Post Thanks / Like

    Re: Electrocution - how does it work?

    The electrical resistance of your body limits current to safe levels when you come in contact with
    lower voltages. Higher voltage, same body resistance =higher current.
    Miller a/c-d/c Thunderbolt XL
    Millermatic 180
    Purox O/A
    Smith Littletorch O/A
    Hobart Champion Elite

  7. #6
    Join Date
    Apr 2014
    Location
    MN/WI
    Posts
    342
    Post Thanks / Like

    Re: Electrocution - how does it work?

    A few milliamps connected to the lobes of your heart might kill you. Through your hands to a ground you probably won't even know it's there simply because the body is not all that good of a conductor. Digital devices with 5 volts and milliamps of current won't get very far unless you are standing in the shower with a tight grip on a plumbing pipe.

    Higher voltage and higher frequency will help the flow through your body. Like the spark jump on a Vandegraph generator high voltage will help carry low amps through low conductivity areas of your body, such as gloves or the skin on your hands and the soles on your shoes. I have heard of industrial accidents where repairmen got careless and forgot to turn off power before grabbing a component with 600 volts and having their fingers burned off/blown off as well as holes in the soles of their shoes and feet.
    https://reference.medscape.com/featu...rical-injuries

    But digital devices with 5 volts and milliamps of current won't get very far unless you are standing in the shower with a tight grip on a plumbing pipe. When working on digital devices we wear a protective strap to protect the device from the electrical charge inside of our bodies, not the other way around.
    Century buzzbox that I learned on 40+ years ago (was Dad's)
    Crappy Century 110volt mig 70 amp pigeon pooper.
    Lincoln Idealarc TIG-300

  8. #7
    Join Date
    Dec 2007
    Location
    Los Angeles
    Posts
    7,812
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Quote Originally Posted by treefondler View Post
    The thought about grounding already came to mind and I tried to get tutor to explain it but I didn't manage to get a thorough enough explanation to understand. He said something along the lines of it not making any difference at all whether a person welding was grounded or not. That the electricity only wants to travel between the two welding cables and no where else. That it would not decide to take a short cut to ground through our bodies because it has no inclination to go to ground, that it goes to the other terminal.

    We all know that in warm & poor countries, the kind of people who weld rarely even own a pair of shoes. And they definitely do not wear gloves. If the current had any tendency to go to ground, surely the operator would be getting electrocuted on a daily basis?
    Your instructor is correct- The electricity always wants to return to where it started. A Circuit. The safety device is thus called a Circuit Breaker.

    Bead-boys has a great explanation but in the scenarios where holes are blown out of shoes it is because the electricity is trying to find its way back to the source and the earth below is sometimes used as a path.

    The electricity isn't trying to find the earth it just happens to be there and is used as a path as it trys to make its way back to the source.

    The Ground rod at yer house is not there to take electricity to mother earth as a safety measure.

    You can search the forum for more explanation on purpose of ground rods.
    Ed Conley
    http://www.screamingbroccoli.com/
    MM252
    MM211 (Sold)
    Passport Plus & Spool gun
    Lincoln SP135 Plus- (Gone to a good home)
    Miller 125c Plasma 120v
    SO 2020 bender
    Beer in the fridge

  9. #8
    Join Date
    Jun 2012
    Location
    CT
    Posts
    4,038
    Post Thanks / Like

    Re: Electrocution - how does it work?

    speaking as a former paramedic who has treated a whole bunch of electric shock victims, electricity kills you in one of two ways. Electricity can disrupt the rhythm of your heart causing something called ventricular fibrillation, which is a form of cardiac arrest. The other way that electricity can kill you is by burns. I once picked up a kid after a hurricane who grabbed on to a downed high tension line. Burnt his arm and both legs off right on the spot. His heart never stopped and he never lost consciousness. Higher voltages are always more deadly that lower voltages and AC is always more dangerous than DC given the same amount of current. Most of the patients I treated after electrocution were awake but badly burned. I only had one that was in cardiac arrest from the shock.

    https://www.brighthubengineering.com...ck-comparison/

    https://www.lincolnelectric.com/en-u...hock-faqs.aspx
    Syncrowave 250
    Purox Metalmaster

  10. #9
    Join Date
    Apr 2006
    Location
    Outside of Raleigh, NC
    Posts
    1,088
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Your skin is a natural insulator that is good for up to 50volts, give or take. That’s why a lot of telecom power requirements are for 48 volts; it’s below the typical body’s resistance threshold.
    Miller Trailblazer Pro 350D
    Miller Suitcase MIG
    Miller Spectrum 2050
    Miller Syncrowave 250DX
    Lincoln 210MP

  11. #10
    Join Date
    Feb 2012
    Posts
    4,173
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Good to know. Hi voltage starts at 65 volts depending on who you ask

  12. #11
    Join Date
    Oct 2014
    Posts
    910
    Post Thanks / Like

    Re: Electrocution - how does it work?

    It takes amps and volts to kill usually. One without the other isn't as bad. High amperage would be like welding leads or car battery lots of amps but little volts. Then the high tension sparkplug voltage has lots of volts but lacks amps. Combine the two though and things gets lively.

  13. #12
    Join Date
    Oct 2019
    Posts
    9
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Quote Originally Posted by Louie1961 View Post
    speaking as a former paramedic ...
    Wow, thanks for sharing..


    I have always had a healthy fear/respect for high voltages, especially after seeing a few videos of people being electrocuted by train power lines. There is no doubt in my mind that a grid power line can burn a whole neighborhood of people to a crisp.

    But its the everyday voltages and currents I am thinking about with this thread. It seems from the posts so far, that safety guidance is massively excessive and based on what happens with unrealistically low resistance in the body plus perfect electrical transmission paths across the heart.

  14. #13
    Join Date
    Sep 2016
    Location
    American Samoa
    Posts
    312
    Post Thanks / Like

    Re: Electrocution - how does it work?

    I have been zapped by the HF start using TIG in my hot sweaty tropical environment, enough to throw the torch across the shop.....it has happened when stick welding also, when my gloves were wet and resting on the part being welded. Shocking experience.

  15. #14
    Join Date
    Nov 2009
    Location
    Arizona
    Posts
    2,627
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Quote Originally Posted by scsmith42 View Post
    Your skin is a natural insulator that is good for up to 50volts, give or take. That’s why a lot of telecom power requirements are for 48 volts; it’s below the typical body’s resistance threshold.
    add some sweat to that skin and the resistance will drop drastically
    Miller Challenger 172
    Miller Thunderbolt AC/DC 225/150
    Miller Maxstar 150 STL
    Victor 100C
    Victor Journeyman
    Oxweld OA
    Harris O/A
    Smith O/A little torch

    No, that's not my car.

  16. #15
    Join Date
    Nov 2009
    Location
    Arizona
    Posts
    2,627
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Quote Originally Posted by Louie1961 View Post
    electricity kills you in one of two ways. Electricity can disrupt the rhythm of your heart causing something called ventricular fibrillation, which is a form of cardiac arrest. The other way that electricity can kill you is by burns.
    There is a 3rd way electricity can kill you, in a lake or a pool it can paralyze your muscles and you drown. This happens every year from mis-wired boats on shore power and from improperly wired pool lights.
    Miller Challenger 172
    Miller Thunderbolt AC/DC 225/150
    Miller Maxstar 150 STL
    Victor 100C
    Victor Journeyman
    Oxweld OA
    Harris O/A
    Smith O/A little torch

    No, that's not my car.

  17. #16
    Join Date
    Nov 2009
    Location
    Arizona
    Posts
    2,627
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Also more people are electrocuted by household voltages than high voltages for several reasons including household voltage is more commonly contacted and often by unqualified persons. Higher voltages are usually dealt with by trained persons.
    Miller Challenger 172
    Miller Thunderbolt AC/DC 225/150
    Miller Maxstar 150 STL
    Victor 100C
    Victor Journeyman
    Oxweld OA
    Harris O/A
    Smith O/A little torch

    No, that's not my car.

  18. #17
    Join Date
    Jun 2017
    Location
    AJO, ARIZONA
    Posts
    3,364
    Post Thanks / Like

    Re: Electrocution - how does it work?

    This last summer we lost power to the house, turns out that a feline type creature ran up the pole that supplies our house & the neighbors place, got accros the lugs on the transformer, we found the hollow burned to a crisp cat a month later when I was picking up all the scrap metal I bought from her, as it turns out the feline belonged to a neighbor down the road and they had been looking for it & finally concluded it got coyote'd, owl'd, bob-cat'd or mountain lion'd, but nope there it lay in all its radiant after life.
    NRA LIFE MEMBER
    UNITWELD 175 AMP 3 IN1 DC MIG/STICK/TIG
    MIDSTATES 300 AMP AC MACHINE
    GOD BLESS AMERICA!
    “Freedom is never more than one generation away from extinction.
    We didn’t pass it to our children in the bloodstream".
    RONALD REAGAN

  19. #18
    Join Date
    May 2014
    Location
    Central Wa. state
    Posts
    3,658
    Post Thanks / Like

    Re: Electrocution - how does it work?

    A few years back I saw a hawk go after a squirrel on a power pole crossbar and get 2 phases of 15KV lines. Flashbulb with a shower of feathers. The sonic boom got the squirrel.

  20. Likes MetalMan23 liked this post
  21. #19
    Join Date
    Apr 2017
    Location
    Long Island, NY
    Posts
    345
    Post Thanks / Like

    Re: Electrocution - how does it work?

    I recall my dad telling me about a guy that got electrocuted while waxing his car with a 120v polisher. Back in the day tools were not double insulated as they are today. They were made of metal and a reversed neutral could cause the body of the tool to be hot. He stepped in a puddle of water from washing the car and that was his end. Thankfully tools are safer today.
    Lincoln Invertec V205-T Tig/stick
    Miller Coolmate 1.3 Coolant System
    Millermatic 211 Mig Welder
    Speedglas Adflo PAPR 9100 FX-Air
    CertiFlat FB2430 fabBlock U-Weld Kit Welding Table
    FW3012 CertiFlat fabWing 30" X 12" Extension Table

  22. #20
    Join Date
    Jun 2017
    Location
    AJO, ARIZONA
    Posts
    3,364
    Post Thanks / Like

    Re: Electrocution - how does it work?

    We had an electrician here back in the 60' got into some 480 IIRC, he lost both arms below the elbow, He adjusted well and blew his settlment on a pretty wild 427 or 454 Chevelle SS, and radicalized the crap out of it, last I heard he was doing rehab for fellow amputees , had none of his settlement money left, his wife had left him .....I i would see him at the bar occasionally shooting pool, he was pretty damn good with the hooks.
    NRA LIFE MEMBER
    UNITWELD 175 AMP 3 IN1 DC MIG/STICK/TIG
    MIDSTATES 300 AMP AC MACHINE
    GOD BLESS AMERICA!
    “Freedom is never more than one generation away from extinction.
    We didn’t pass it to our children in the bloodstream".
    RONALD REAGAN

  23. #21
    Join Date
    Dec 2013
    Location
    Mount Tabor VT
    Posts
    6,908
    Post Thanks / Like

    Re: Electrocution - how does it work?

    In the worst conditions the human body is a poor conductor.

    Lets go to the basics:
    Voltage is electrical pressure
    Amperage is electrical current
    Wattage is volts times amps.

    A low voltage source will not have enough pressure to push much current through human flesh.
    Shock is always through a person. It takes two points of potential. If the path is primarily through non vital organs, it may not kill despite tremendous current (amps).

    Personally I have experienced voltage up to 240, and much higher instantaneously. The worst would have measured 120 from right to left hand. I was unable to let go for an extended period, maybe two minutes. I suffered severe muscle strain in forearms, but little else.

    I work with live power too often. I may not be giving proper respect, but don't worry much about incidental shocks from 240 volt supplies. The 480, on the other hand, I have nightmares about. You treat that like a rattle snake.

    Here, we ground the center tap of 240, so the most common shock is to ground of 120 volts.
    In WYE connected three phase 480 Volts, to ground is 277.

    Use care, follow safety rules. You'll likely get a few shocks in your life, but live.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  24. #22
    Join Date
    Nov 2009
    Location
    Arizona
    Posts
    2,627
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Those of us who work with it every day tend to get complacent and or lazy, we work with it every day which increases the odds of electrocution immensely. I have to drive it into the heads of my workers, don't be lazy, shut it down. Why risk your life to save a few minutes? Very, very few if any at all, legitimate reasons to work it live.
    Miller Challenger 172
    Miller Thunderbolt AC/DC 225/150
    Miller Maxstar 150 STL
    Victor 100C
    Victor Journeyman
    Oxweld OA
    Harris O/A
    Smith O/A little torch

    No, that's not my car.

  25. #23
    Join Date
    Jul 2018
    Location
    Cumbria, UK
    Posts
    935
    Post Thanks / Like

    Re: Electrocution - how does it work?

    I've touched a live 240V terminal a couple of times in my life, accidentally. Luckily always with dry skin, so I got a good belt of a shock but not enough current to cause harm.
    That's true 240VAC to ground, not centre tapped.

    I've never touched a 415v 3 phase connector yet, touch wood. Although each phase is still just 240V. Would be incredibly unlucky to grab a second phase at the same time.

  26. #24
    Join Date
    Sep 2011
    Location
    Jasper TX
    Posts
    1,572
    Post Thanks / Like

    Re: Electrocution - how does it work?

    The worst shock for me was the neutral of a 277 vac lighting circuit. For me, things slowed down and I could feel every one of those 60 cycles. My whole body went rigid until my helper jerked the wire out of my hand. Every muscle in my body hurt for the next week.
    Owner of Fast Leroy's Bar and Grill
    Liquor up Front, Poker in the Rear

  27. #25
    Join Date
    Dec 2013
    Location
    Mount Tabor VT
    Posts
    6,908
    Post Thanks / Like

    Re: Electrocution - how does it work?

    Quote Originally Posted by Munkul View Post
    I've touched a live 240V terminal a couple of times in my life, accidentally. Luckily always with dry skin, so I got a good belt of a shock but not enough current to cause harm.
    That's true 240VAC to ground, not centre tapped.

    I've never touched a 415v 3 phase connector yet, touch wood. Although each phase is still just 240V. Would be incredibly unlucky to grab a second phase at the same time.
    Here much of the power we use, whether non commercial, or commercial having passed through an in building transformer is 240 volt single phase. Most of these systems, pretty much 100% of households have a center tap in that secondary winding. "Cutting the sandwich in half". This provides 120 volt power from 240 volt transformer. This is referred to in code as the "grounded conductor" It limits shock to ground to 120 volts. It is more common to contact a grounded item and a live item simultaneously. Less common to touch both legs of the transformer connected power at once.

    I will presume some leg of your power in UK is grounded. I've never been there, I'm not familiar with your system.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Page generated in 1,603,562,347.98580 seconds with 12 queries