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Re: very long sparks

100+ meters free air.. Outdoors in Siberia.. The impulse generator is a
large round building in a field near some test transmission lines (130 kV
class) on standard towers. The generator appears to be of the same general
height as the tower. The spark goes up from the impulse generator and
curves over and down to the transmission tower. The text isn't clear on the
energy, but in the same paragraph they talk about 100 to 1000 kJ energies.
The photo isn't big enough to find something for absolute scale (like a 6
foot person standing in the snow), but, as a guess, I'd say that generator
was about 100 meters from the tower, and the spark was probably 50% longer
given the curvature.

I'll scan the photo and post it and hope the copyright gods don't smite me
(hey.. it's "fair use" in review and comment.)

I'll also see if they have a reference to the source of the photo and maybe
I can get the library to get a copy..  It is MOST impressive...

----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: very long sparks
> Date: Thursday, January 06, 2000 12:42 AM
> 
> Original Poster: "Dr. Resonance" <Dr.Resonance-at-next-wave-dot-net> 
> 
> to: Jim
> 
> If this was an impulse test, question:  Was the spark in free air or
across
> a string of insulators?  If across a string of insulators I have
stretched
> 1,000,000 volts to over 23 feet, but that doesn't count as a free air
spark.
> 1 MEV in free air at 250 KHZ with a break rate of 450 PPS at a power
level
> of 7.5 KVA will stretch to approx 9 feet.
> 
> Perhaps someone on the list that has a copy of the book could comment on
> whether it was a 100 meter free air discharge or 100 meters creepage
> flashover along an insulator string.
> 
> Regards,
> 
> Dr. Resonance
> 
> 
> 
> -----Original Message-----
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
> Date: Wednesday, January 05, 2000 5:03 PM
> Subject: very long sparks
> 
> 
> >Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
> >
> >The longest artificial sparks that I am aware of were NOT produced by a
> >tesla coil, but were produced by (very) large impulse generators. Les
> >Renardiers group in France built a generator in the 8-9 MV range which
> >produced long sparks (I'd expect >50 meters, but I don't have the
reference
> >handy), and in Bazelyan and Raizer ("Spark Discharge") there is an
> >impressive photo of a 100+ meter (thats meters, folks, not feet) spark
in
> >an outdoor test lab. Put it this way, the spark is much longer than the
> >height of a standard looking HV transmission tower..
> >
> >As a practical matter, once you get above about a megavolt, the linear
> >distance/voltage relationship goes away (mostly because you are in a
> >non-uniform/needle gap situation).  Not much voltage increase gets you a
> >very large distance increase. This is of great concern to those
designing
> >EHV substations because the clearance distances get phenomenal.  At
these
> >voltages, the amount of energy behind the spark (mostly from Ctop in
your
> >Tesla coil) determines how far it can propagate.
> >
> >Greg Leyh's Electrum made fairly long sparks (20 meters?) and Bill
Wysock's
> >big coils that kVA Effects ran last year(?) also could make sparks in
this
> >range, but this is using pretty much state of the art components
> >(particularly caps, wire, and forms). I doubt that you'd get much
farther
> >unless you basically built some sort of high-rep rate impulse generator.
> >
> >
> 
>