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Author Topic: Rock Singer Electrocuted On Stage  (Read 19684 times)

Mike Sokol

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Re: Rock Singer Electrocuted On Stage
« Reply #20 on: November 28, 2014, 01:15:56 pm »

I can't imagine any safe high voltage bare hand work except perhaps for science fair Van de Graf demos...

Or crawling out of a helicopter to inspect live high-tension wires at 765,000 volts.  ;D

https://www.youtube.com/watch?v=SkFH8lLvKZ0
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Mike Sokol
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John Roberts {JR}

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Re: Rock Singer Electrocuted On Stage
« Reply #21 on: November 28, 2014, 01:23:16 pm »

Or crawling out of a helicopter to inspect live high-tension wires at 765,000 volts.  ;D

https://www.youtube.com/watch?v=SkFH8lLvKZ0

I'd need gloves and a diaper to do that.... :-\

JR
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Mike Sokol

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Re: Rock Singer Electrocuted On Stage
« Reply #22 on: November 28, 2014, 04:37:17 pm »

I'd need gloves and a diaper to do that.... :-\

JR

Live high tenion power line inspection is a pretty common thing now, but can you imagine what it must have been like for the first guy to try this? I'm sure they started with a relatively low voltage line a few feet off the ground and worked their way up. But somebody had to be the first one to climb out on a live wire with half a million volts on it. Plus the guy flying the helicopter has to have nerves of steel. If ANYTHING goes wrong, I'm pretty sure there would be a rather large fireball.

Even though I could intellectually convince myself that this would be safe, I think that JR is correct about needing a diaper. This is some crazy stuff...  :o
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Steve Bradbury

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Re: Rock Singer Electrocuted On Stage
« Reply #23 on: November 28, 2014, 05:37:41 pm »

Quote
One way I considered was sensing current in the ground wire and disabling the device when current above a set threshold was detected-with say a shunt trip type of circuit breaker.  While that may seem extreme-if current is flowing in a ground wire the right course of action is to stop using the gear and fix the problem.

The problem is not current leaking through the earth wire but current leaking through people. Monitoring the current in the earth wire would not detect this. Also if the earth wire became open circuit no current would flow so the device would never trip. By sensing the difference between the incoming current and the return current in what should be a closed loop any leakage out of that loop above the threshold will trip the device irrespective of where it is going.

After watching this video I thought I’d have ago at washing my electric sockets with a jet washer. (not really)
http://www.youtube.com/watch?v=lcjhjna9jZE
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Mike Sokol

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Re: Rock Singer Electrocuted On Stage
« Reply #24 on: November 28, 2014, 06:11:26 pm »

Here's a REALLY BAD video recreation of Agustín Briolini being electrocuted by "faulty wiring on the microphone". Of course, it's impossible for the accident to have happened as illustrated, but the general public won't know that.  https://www.youtube.com/watch?v=EUgb3vEztiY
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Stephen Swaffer

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Re: Rock Singer Electrocuted On Stage
« Reply #25 on: November 29, 2014, 12:07:24 am »

The problem is not current leaking through the earth wire but current leaking through people. Monitoring the current in the earth wire would not detect this. Also if the earth wire became open circuit no current would flow so the device would never trip. By sensing the difference between the incoming current and the return current in what should be a closed loop any leakage out of that loop above the threshold will trip the device irrespective of where it is going.

I understand and agree-that is exactly what GFCIs do-but when gear leaks current to ground, then people blame the GFCI and bypass them.

I doubt current sensing and shunt trip would have a practical use in this situation-unless perhaps in the scenario where AC current traveling to ground through mic/line shields would shut down a mixer calling attention to the issue.  But fusing the ground -while stopping the current flow through that path-leaves the source of the current energized and the artist would have no clue they were holding a potentially lethal situation on their hand, just waiting for another unfused ground.
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Steve Swaffer

Steve Bradbury

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Re: Rock Singer Electrocuted On Stage
« Reply #26 on: November 29, 2014, 12:26:40 pm »


Steve,

The problem with inherent leakage from modern electronic equipment and the knock on effect of unintentional breaker tripping has been discussed on other threads. Whilst that is no reason to continue discussions I am reluctant to continue going further off topic given the tragic reason that prompted this thread.

No doubt the subject will be discussed again in the future.

An interesting web page discussing power quality. The link is to the contents page, if you scroll down there are sections on leakage and nuisance tripping.

http://www.marcspages.co.uk/pq/0000.htm
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Art Welter

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Re: Rock Singer Electrocuted On Stage
« Reply #27 on: December 03, 2014, 10:14:49 am »

+100%

I, for one, want anything connected to AC power or potentially energized by power to have a low-impedance Equipment Grounding Conductor (EGC) back to the service panel's Ground-Neutral-Earth (G-N-E) bonding point.

Of course, GFCIs are required by code in many of these powering situations, but as note by others, that's really a secondary line of defense. A solid ground is your best friend when you're standing on a stage surrounded by AC powered sound and lighting gear.
Mike,

Microphone chassis are almost always connected to pin 1 of the XLR connector. Pin 1 is normally connected to the shield wire, which is normally connected to the mixer chassis, which generally is connected to earth ground.

In the case of a guitar amp that has been "ground lifted" with either a "cheater plug" or a removed earth ground (intentionally or accidentally) and then has has a neutral/hot swap (plugged in backwards, stage power miswired) the solid ground connection provided by the microphone chassis is definitely not your best friend, and can cause death when some part of your head contacts it while holding the hot guitar.

With rubber sole shoes on a non-metal stage a guitar player may not feel any tingle with an energized guitar until contacting the earth ground provided by the mic.

In this case, the guitar player's "best friend" could have been the venerable Shure 565D Unisphere I microphone, designed in an era when "accidents" such as the one in the OP were daily occurrences at venues all over the world.

As engineers, we must be vigilant to "protect the innocent", most guitar players using vintage 1969 Woodstock era amps don't realize that the plastic ring isolating the windscreen on the mics used at that festival also protected the performers from electrical shocks, as long as they did not touch the mic shaft and their guitar strings at the same time.

I've said it before, I'll say it again- if you don't bother with any other test equipment, all it takes to avoid a tragedy is to hold the plugged in guitar by the non conductive wooden body, and lightly touch a string (coming out a tuning peg) to the mic screen, then the mic shaft, sparks will fly if there is a serious problem, and lots of amp noise will usually result even on minor voltage differences. If you hear or see those problems, track them down. Often the culprit will be the guitar player's beloved amplifier.

Art
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Stephen Swaffer

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Re: Rock Singer Electrocuted On Stage
« Reply #28 on: December 03, 2014, 01:27:41 pm »


In the case of a guitar amp that has been "ground lifted" with either a "cheater plug" or a removed earth ground (intentionally or accidentally) and then has has a neutral/hot swap (plugged in backwards, stage power miswired) the solid ground connection provided by the microphone chassis is definitely not your best friend, and can cause death when some part of your head contacts it while holding the hot guitar.


Why should an engineering safeguard (solidly grounded mic) be blamed because someone intentionally or carelessly defeats another engineering safeguard?

When I started working in maintenance in a factory, I grabbed a a hammer drill from the cabinet and tried to use it-getting shocked in the process.  One of the old timers told me, "Ohh yeah-that drill bites."  It didn't bite much longer-I got permission to get rid of it.  The hazard wasn't as much the drill (or guitar amp) as the attitude that "that piece of gear bites."  If it bites or tingles (or trips the GFCI that should be used) ever-FIX  it or pitch it!  Is the cost or time worth your life-or someone elses?
 
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Steve Swaffer

George Friedman-Jimenez

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Re: Rock Singer Electrocuted On Stage
« Reply #29 on: December 03, 2014, 03:14:46 pm »

I am repeating myself but I prefer the capacitor vs fuse to provide a shield ground, and might like the fuse solution better if such tiny fuses were more common, cheaper, and certain. Fuses operate by thermal overload and the stress from a few mA even at 100V is not a lot of heat power. An electronic breaker could be very sensitive and even resettable, but expensive and solid state devices have a bad tendency to fail as a short circuit. So I prefer the low tech capacitor to current limit the AC fault
Caps can fail too, but a small film cap failing as a short is rare, and they make caps specifically for use around main voltage.   
JR
PS: Some chatter from Argentina, but no real new information yet.

This seems like a solid argument in favor of industry wide adoption of protective technology to prevent these sorts of electrocutions. Why has this not happened yet?
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Re: Rock Singer Electrocuted On Stage
« Reply #29 on: December 03, 2014, 03:14:46 pm »


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