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#123986 - 06/23/06 07:21 PM Tent OOPS!!!
Scott35 Offline

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Registered: 10/19/00
Posts: 2707
Loc: Anaheim, CA. USA
*** Submitted For TwinCitySparky ***

****** TENT OOPS!!! ******

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Hello!
I thought this might be good for the photos for discussion area.

Last Thursday, while working at a church, the maintenance coordinator walks up and asks for my opinion.
We walk outside and he shows me this tent that they just put up for their big anniversary celebration.

He said the 25 tent assembly guys who were putting it up were continually getting shocked, as they touched the metal poles and such.

The parking lot lights were marked and de-energized.

The tents imbedded power/lighting cords that were not connected to anything, were humming and buzzing!

I gave a brief explanation of inductance, pointed up at the 72KV ?? lines and said I thought they might want to move the tent.

An hour later, after he talked to 2 masters at different companies, he approached me again with the tent assembly personnel and said:

"One master told him grounding the tent would help."

I pointed at the 150 or so 10' steel anchors that they jackhammered into the parking lot around the tent and said:

"Might not help much".

He then said another master told him that the POCO could place rubber maintenance service covers over the wires to lessen the effects and danger!

I then said I thought he should contact the POCO right away.

After hearing them say MOVE IT NOW! He decided to shoehorn it into a distant lot.

The tent personnel said they never ran into this before!!!

I wonder who will pay for the move? The 3rd pic shows tent after being moved.

Yikes!

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*** Moderator's Note: Thanks to TwinCitySparky for the submissions!

New / Posted 06-23-2006 by Scott35
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#123987 - 06/25/06 07:09 PM Re: Tent OOPS!!!
alan bergold Offline
Member
Registered: 11/20/01
Posts: 42
Loc: east meadow ny
I cant believe that happened ,the power lines are at least 20 feet from the tent,are you sure thats why they were getting zapped,and if so how bad were the shocks and was it a wet day .??????
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#123988 - 06/25/06 07:25 PM Re: Tent OOPS!!!
e57 Offline
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Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
I think they are 30-40' from the tent, but poles are 20' closer to them than someone on the ground. I think that difference in potential/distance could be enough for a small zap.
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#123989 - 06/25/06 07:29 PM Re: Tent OOPS!!!
Dnkldorf Offline
Member
Registered: 12/12/04
Posts: 1064
Loc: nowhere usa
I would wonder if they have the same problem with the light poles in the picture?
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#123990 - 06/26/06 03:55 PM Re: Tent OOPS!!!
JoeTestingEngr Offline
Member
Registered: 11/04/05
Posts: 781
Loc: Chicago, Il.
I think this is definately one of those places where the Fluke and the Wiggy will get you different readings. The light poles are at right angles to the wires so I doubt there is much coupling.
Joe
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#123991 - 06/26/06 04:47 PM Re: Tent OOPS!!!
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
Joe....
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#123992 - 06/26/06 11:34 PM Re: Tent OOPS!!!
TwinCitySparky Offline
Member
Registered: 03/23/06
Posts: 52
Loc: Minnesota
No rain or moisture at all. The poles are about 30'- 40' feet from the wires. The lot lights which are parallel to the lines but further away did give me a "lighter" version of the shocks happening at the tent when I was replacing bulbs. The shocks at the tent were intense enough to cause discomfort. It's hard to tell from the pics but the tent poles are about 10' higher than the lot lights and as you can see, the position of the tent is actually beneath the lines. I was able to draw almost a 1/2" arc from the poles. Every 2nd or 3rd cable that was sewn in to the tent was vibrating intensely. I was surprised they were almost done putting it up. That must have been a long day for the workers as they repeatedly got shocked. They were trying to complete the building process by pushing each of the main tallest poles into a perfect vertical position. That is when the shocks became even more intense and they finally thought they should ask someone about it.

[This message has been edited by TwinCitySparky (edited 06-27-2006).]
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#123993 - 06/27/06 05:56 AM Re: Tent OOPS!!!
mamills Offline
Member
Registered: 11/30/01
Posts: 745
Loc: Wharton, Texas, USA
I don't know the slightest thing about any of this, so somebody please set me straight. Could this be caused by some type of leakage from one of the insulators on one of these towers (even though I'm assuming that these towers are supposed to be grounded)?

Also, I wonder if the tent setup people got as far as they did because they were wearing gloves while working?

Mike (mamills)
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#123994 - 06/27/06 02:48 PM Re: Tent OOPS!!!
Rewired Offline
Member
Registered: 01/01/06
Posts: 558
Loc: Hamilton, Ontario, Canada
Mike:
The whole thing is acting like a transformer in a sence.... The current flowing in the lines overhead is creating a magnetic field around each of the lines ( in this case a very strong one).. The magnetic field in turn is now generating (inducing) a voltage in the metal work of the tent poles and lighting and power cords and what ever was present at the time...
There is no electrical "leakage", its just being in the wrong place period..

Personally I am amazed that Twincitysparky was able to draw a 1/2 arc off one of the poles.. What was I told once,roughly 33,000 volts jumps something like a 1" air gap???? ( depending on conditions) So that would equal about 16,500V present at the poles, albeit the current would be so minimal it would be very uncomfortable to be in contact with, yet still VERY unsafe..

A.D
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#123995 - 06/27/06 05:39 PM Re: Tent OOPS!!!
Larry Fine Offline
Member
Registered: 02/18/05
Posts: 693
Loc: Richmond, VA
For effect, have someone hold a fluorescent tube inder the lines.
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