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Topic Title: USA - Another incident of electrocution in water
Topic Summary: Boats and swimmers! 3 kids involved this time.
Created On: 17 August 2012 07:49 AM
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 17 August 2012 07:49 AM
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Jaymack

Posts: 4586
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This type of incident happens from time to time in the USA.

"Three children were electrocuted in separate incidents in Tennessee and Missouri on Wednesday.

A sheriff in East Tennessee now says one boy swimming in a marina at Cherokee Lake was electrocuted and a second one was revived on a life flight out of the area.

Originally police reported that both boys had been killed.

According to CBS News affiliate WVLT Knoxville, Jeffrey Atkins, Grainger County EMA director, said that four children were swimming between house boats. A woman witnessed two of the children appearing unconscious. As she tried to help, the woman felt a surge and retreated.

Grainger County Sheriff Scott Layel tells the station that the boy who died was 10 years old and the revived boy is 11.

The sheriff's office says it happened around 2:15 p.m. near the German Creek Marina in Bean Station. Police say an additional six to eight people were taken to the hospital in Morristown to be checked out.

The marina has been evacuated as authorities conduct their investigation.

Meanwhile, two Missouri children have died after coming into contact with electricity while swimming at the Lake of the Ozarks on the Fourth of July.

The Missouri State Highway Patrol identified them as 13-year-old Alexandra Anderson and her 8-year-old brother Brayden, of Ashland.

The Patrol says the children were swimming near the 6.5 mile marker in the Gravois Arm of the lake when they were electrocuted by an "unknown source of electricity" just after noon Wednesday."


http://www.cbsnews.com/8301-20...ectrocuted-in-tenn-mo/
 19 August 2012 09:57 AM
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OldSparky

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so what would cause this then?
 19 August 2012 02:03 PM
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dbullard

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Could it be the locality of possible " electric fishing" seems the southern states have a "no holds barred" mentallity to how they fish, I do know in the UK for sampelling the rivers the havea genny mounted in the boat and put a current into the water to stun / kill fish to check population density, maybe someone tried the same over there ???

Tragic either way


Regards

Daren

-------------------------
..... Dont pee in my pocket and tell me its raining ......


www.quest-electrical-sw.co.uk
 19 August 2012 03:13 PM
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AncientMariner

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I cannot speak for that part of the USA, but I understand that in some areas single-phase domestic supply is derived from single-wire earth return HV. I have seen this distribution method in South Korea and seem to remember being advised that similar used in USA and else where. In fact I do remeber noticing around Boston that where there were pole mounted HV to LV transformers, would be three off single phase transformers with single HV insulator on each. The three tanks then being connected to a star point which earthed - for that arrangement only the out of balance HV current would return via the ground connection. However, for single phase single HV wire the ground current would equal the phase current.

So, could this explain the rather tragic accidents?

After I posted the above, I remembered that there are many HVDC systems which use an earth return.

This is an interesting article which covers the technicalities of a 2,400 amp earth return current.

http://www.labplan.ufsc.br/con...gre06/DATA/B4_206.PDF

Cheers!

Clive

-------------------------
Clive S Carver GCGI IEng MIET

Edited: 19 August 2012 at 03:57 PM by AncientMariner
 19 August 2012 03:59 PM
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alancapon

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It could do. One of the shortcomings of the American HV configuration is that it is not possible to detect earth faults on the HV network. With a distributed neutral, it is impossible to tell the difference between an "out of balance" neutral current and an earth fault until something either catches light, or draws enough current to operate a fuse.

Although I wouldn't recommend demonstrating it, using the American configuration a downed HV conductor has a 99% chance of being live, using the British configuration, it has more that a 90% chance of being dead, due to the extensive use of "Sensitive Earth Fault" protection.

Regards,

Alan.
 19 August 2012 10:54 PM
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westfield6

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Originally posted by: OldSparky

so what would cause this then?


The clue is "swimming between houseboats". Almost certainly faulty or no earthing of one of the houseboat supplies. Any leakage to the hull would then flow through the water where the swimmers were.
 19 August 2012 11:23 PM
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OldSparky

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Originally posted by: westfield6

Originally posted by: OldSparky



so what would cause this then?




The clue is "swimming between houseboats". Almost certainly faulty or no earthing of one of the houseboat supplies. Any leakage to the hull would then flow through the water where the swimmers were.



of course.. on boats they have an earth plate in the hull, i guess if all is well this is not a problem, but under fault conditions the water around the boat would be live i guess
 20 August 2012 11:24 AM
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AJJewsbury

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There were several similar reports here a while ago - the Americans had a habit of using PME-like system, in the past even extending the CNE as far as some large appliances, so a single poor joint can create a significant p.d. between different local earths (or in the case of a steel hulled houseboat, waters). I think the problem is more pronounced with swimmers in fresh rather than salty water - as fresh water has a higher resistance, more current passes through the swimmer rather than going around the swimmer in the water.
- Andy.
 20 August 2012 02:50 PM
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AJJewsbury

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 20 August 2012 05:27 PM
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rocknroll

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I think the problem with boats and stray and leakage currents is a little more complicated than your cottages where you throw a couple of RCD's and an earth rod at it and hope it works, a friend of mine who is on his way back from Greece with a 4 berth catamaran which I hope to join in Spain providing he gets there before the Oct 1st deadline and sail back had a lot of problems in this area with his previous boat, stray currents and leakage current around a boat are common, we even tried double poling everything after scrounging some test equipment off a marine electrician, there are various types but the SeaBiss seems to be a popular model, you connect it to the supply dangle one end in the water or connect to underwater metal and the other lead has a crocodile clip which you connect to various earthing points around the boat, double poling did make a slight difference but marginal. Just to point out that both sea and fresh water in boat areas are highly conductive, they both contain minerals that act as an electrolyte and marinas, boat yards, harbours etc, contain many metal elements that corrode, boats, pilings, chains, anchors, anodes etc, including the rubbish on the bottom so the water has a lot of metal particles in it.

Local authorities here and across the pond go to great lengths to survey and designate no swim zones in these areas and even put up signs explaining why, so I suppose its down to Darwin again if you dont take heed of the safety advice then you are on your own.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 21 August 2012 06:19 AM
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Jaymack

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Some more information on this incident from the link at the end of this post.

Quotes: -

"With my digital voltmeter, I went to the area where Lucas had been, put the negative lead to a ground, dropped the positive lead into the water, and immediately got AC voltage," he wrote in an essay about his son's death. "I notified the Sheriff's Department, reporting what I had found and that I wanted to get someone to confirm my test. They agreed to send out some deputies while I called in an electrician. He arrived later that morning, tracing the electricity to a powerboat that was in the area where the kids had been swimming."

"In the throes of grief, Ritz, now a marine electrician, started agitating for safer marinas. It infuriated him, for example, that electrical outlets at marinas were not held to the same standards as outlets in bathrooms."

"The European market has had ground fault protection in their marinas - the power coming into the marina at the docks - for over 25 years," Ritz told msnbc.com. "How come we can't have that?"

"The obstacles are many, however. Ritz said that a marina manager near where he lives wanted to upgrade some of the marina's electrical system but learned that, by law, he would also have to upgrade the whole system - a pricey proposition."

http://usnews.nbcnews.com/_new...shock-to-swimmers?lite
 21 August 2012 06:21 AM
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Jaymack

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And some more information is here: -

http://www.boatus.com/seaworthy/kritz.asp
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