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Name: Gordon
Status: Student
Grade: Other
Location: FL
Country: United States
Date: Winter 2009-2010


Question:
As wildland (forest) firefighters, we are commonly taught that heavy smoke around high-voltage lines can hasten 'arc to ground' due to the carbon in the smoke. A less-common theory that is making the ways through our community is that heat (air temp.) not smoke determines the likelihood of a high-voltage line arcing to ground. Is there any validity to either/both of these theories?



Replies:
Hi Gordon,

I suspect the reason is neither of the theories you have suggested. I really doubt that the carbon particles in smoke makes any difference since there would seem to not be enough of them (compared to the amount of air molecules) to increase the conductivity of the air. Also, the temperature increase you refer to will not make any significant difference unless the voltage was high enough, and the high voltage line was close enough to ground, that it was almost ready to arc before the smoke surrounded it.

I suspect the real cause could be the ionized particles in smoke that might trigger a flashover. But even then, I wonder how much of this problem is fact, and how much is unsubstantiated urban legend.

Regards,

Bob Wilson



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