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Increasing demand factors in residential
by tortuga - 03/28/24 05:57 PM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
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This is a new one
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Few pics I found
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Joined: Oct 2000
Posts: 2,749
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http://www.themeterguy.com/photogallery/NewPics/Index.htm

See the clip showing the crane short!


Joe Tedesco, NEC Consultant
Arc Flash PPE Clothing, LOTO & Insulated Tools
Joined: Mar 2001
Posts: 2,056
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Damn! I hope nobody was hurt.

Joined: Apr 2002
Posts: 2,527
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Moderator
Joe, are you referring to this link?
http://www.themeterguy.com/photogallery/BoomTruckinPowerLines.wmv {Windows Media}

It's an extra-bad Monday waiting to happen again all over.

Joined: Apr 2001
Posts: 507
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That's some wild stuff!

GJ

Joined: Jan 2002
Posts: 1,457
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WOW!! [Linked Image]

Joined: Mar 2002
Posts: 360
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Member
Hello? Boss?

Um, about the truck.

I think I will need a ride home.

[Linked Image]

Joined: Aug 2002
Posts: 29
F
Member
Shouldnt an OCPD prevented all of that?

Joined: Apr 2002
Posts: 2,527
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Moderator
As for overcurrent protection, medium-voltage utility-type overcurrent protection is a different breed compared to that of typical low-voltage circuits and equipment. For one, sometimes ground-fault/earth-return currents can be below the settings or ratings of overcurrent devices. This may indeed result in flaming tires on incompetently controlled sign trucks.

This is in opposition to how we usually think of equipment grounding and bonding. Besides low current, it is very likely that the potential differences between the crane and the ground mat at a remote source will be large enough to seriously shock or electrocute those standing on the ground in the vicinity of the fault, though not touching any conductive surface short of your shoes contacting the surrounding earth. The rules are different, but in most cases well understood by folks routinely working in medium-voltage applications in utility settings.


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