Interesting info. Thanks for posting. You are the 4th or 5th person to
correct me. :)
In the old daze in the USAF I worked on the F106. It had a radar system
that used pressurized waveguides and dome over the klystron unit to prevent
arcing at altitude.
Keith
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Lux
Sent: Monday, July 26, 2004 1:26 PM
To: keith@dutson.net; TowerTalk
Subject: RE: [TowerTalk] Power lines, hawks, and fire ignition(slightly
off-topic)
At 12:45 PM 7/20/2004 -0500, Keith Dutson wrote:
>I saw that on the news this morning and figured it must be a joke. Or,
>maybe the political news is getting so stale that they dreamed up
>another sensational story. :)
>
>AFAIK it takes about one million volts to jump an inch arc in air at STP.
>However, once a path is established, such as ionized air, the required
>potential drops drastically. Perhaps the bird hit one line and left a
>trail of blood in the air to a second line whereby the arc could form.
>
>Keith
In a uniform field gap, it takes about 71 kV to jump an inch. A uniform
field gap is closely approximated by electrodes where the radius of
curvature is much greater than the spacing (say, two 12" spheres separated
by an inch)
Needle point gaps are roughly 1/3 the voltage of a uniform field gap.
Lower air density reduces the breakdown voltage roughly in proportion.
Air density is reduced either by altitude or higher temperatures. A good
rule of thumb is that the air pressure is reduced by half for every 18,000
ft elevation change.
High humidity increases(!) the breakdown voltage (but reduces the surface
resistance, so creepage breakdown is more likely)
Spark Breakdown cannot occur below about 300V in air, no matter how close
the electrodes are, or how low the pressure is.
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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