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Re: very long sparks
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.
>
>