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#150341 - 02/21/05 01:28 PM How Far Will Electric Lines Arc?
Jim Patterson Offline
Junior Member

Registered: 02/21/05
Posts: 2
Loc: Denver, CO, USA
How far will OH lines carrying 7.2 kV arc? I have a technical reference that states it will arc 3/8" per kV, but an employee challenged my position, stating that distance could be increased by such factors as blowing dust, rain/snow, and magnesium chloride from DOT snow plows. We know the OSHA rule od 10 feet for lines of 50 kV, with multipliers for voltages above that, but I wish to know what your experience tells you.

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#150342 - 02/21/05 11:36 PM Re: How Far Will Electric Lines Arc?
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Gidday there Jim,
Welcome to ECN, mate!.
I work on Live 11kV-66kV lines as a course of my daily work, as a Line-Mechanic here in New Zealand.
Now, the flash-over distance is a function of the E-M fields that surround a conductor that carries a current, where an earthed (Grounded) part, enters that field.
With 11kV here, we are required to have a clear working distance from bare, live lines of at least one metre (3ft), until such time as the lines are sleeved and covers are in place.
That is working from an IEWP (Insulated Elevated Work Platform).
Full PPE is required even after the gear is in place.
Even then, most of our work is still done via Hot-Sticks.
The further you can keep yourself away from that sort of energy, the better.
It hath no friends once it escapes
Bjarney or Charlie, may be able to prove me wrong.
If they can, please guys, bring it on!.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#150343 - 03/15/05 10:55 PM Re: How Far Will Electric Lines Arc?
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
 
Aaak! Sorry for the month-late reply. Legally, US electric-power workers at that voltage are bound by table R6 minimum approach distance in 29CFR1910.269 (OSHA utility rules) at www.osha.gov which ranges about 2 ft. 1 in. to 3 ft. 6 in. for the voltages listed by the OP. For wind and rain, it can be MUCH more critcal. Most contaminants would intuitively seem to worsen the situation requiring greater clearances. For inorganic salts, you might as well swimming in a pool of mercury‚ÄĒthat‚Äôs anybody‚Äôs guess; extremely dependent on concentration and best avoided if at all possible.




[This message has been edited by Bjarney (edited 03-16-2005).]

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#150344 - 03/16/05 01:47 AM Re: How Far Will Electric Lines Arc?
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
YaY!!,
Welcome back Scott!.
Nice to have you here.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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