Re: Official air breakdown voltage?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mike" <induction@xxxxxxxxxxx>

Hi Terry, All,
                    I was doing further reading on this and hit on 
Google this article.
http://www.haefely.com/pdf/scientific/e1-19.pdf  which is a study on 
humidity and under certain conditions.
Also polarity seemed to be a player to the conditions; I was 
searching for more info on the AC breakdown aspects and such but when 
I got an interesting hit it was a "buy me" thing from an IOP paper site.
Still, you may find the free one linked to above interesting, at 
least that one is available.
There was another paper, also a buy me type, that had some method of 
detecting just before the gap fired and switching 7 us before then to 
a ball gap to avert the strike 3 us before it happened.
In that one, there was a 150 us rise time of the main charge (DC) to 
the gap, their mention of detection but the free part ended there.
I wonder if it was some pickup for audio near the gap, listening to 
corona, like you hear on a AM radio just before a nearby strike? I've 
heard those tones grow from a slow growl to a high pitch scream over 
a few seconds then a close by lightning strike.


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, November 25, 2005 7:43 PM
Subject: Re: Official air breakdown voltage?


> Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi Jason,
>
> There is a "very official" way.  Up until recently, high voltages 
> were "officially" measured with ball sparks gaps since that is all 
> that worked scientifically and repeatably.  A pretty official chart is here:
>
> http://hot-streamer.com/TeslaCoils/Misc/SGapVolt.jpg
>
> 3MV/Meter is also almost a "standard" value...
>
> Problem is, voltage fields stretch, bend, and distort....  So given 
> a particular situation, figuring out the breakdown voltage can get 
> super messy!!!  There are fancy computer programs that can do it 
> pretty well but it takes like an EE degree to run them...  Some Ph.D 
> folks can do it on paper...  The functions are NOT straight lines at 
> lower (~10kV) voltages either....
>
> But all that is for "DC"......  With "AC", we can cut arc channels 
> through the air and spoil all the those rules anyway.  It still can 
> be figures out buy some high voltage AC gurus, but it is getting to 
> the technical nightmare level at that point.  Over the decades, 
> Tesla coilers have made "rules" based on observations like John 
> Freau's formula that get "us" through without too much brain damage.
>
> So for DC, the chart above does well.... (It works OK for 60Hz stuff 
> too) There are some "rules of thumb" out there....  Beyond that, 
> there are very messy methods only a few can figure out.  Beyond 
> that, the answer is pretty close to NO....
>
> Cheers,
>
>         Terry
>
>
>
> At 12:51 PM 11/25/2005, you wrote:
>
> > I have read all over the net, around 25KV/inch  <<I use this one
> > I read on one place,           around 30KV/inch
> > Now i have just been told    around 30KV / cm  !!!!   Thats 3 times 
> > the voltage I have been told
> >
> > It is common sense that air pressure, humididty, current, and time 
> > of day all affect air breakdown voltage, but:
> >
> > IS there any official way to determine exactly what air breakdown 
> > voltage is? ( such as KV/distance )
> >
> > _