Re: 1pF+220k....

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Jim, Terry,

On 2 Jul 2005, at 17:06, Tesla list wrote:

> Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>
> At 02:59 PM 7/2/2005, Tesla list wrote:
> >Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
> >
> >Hi All,
> >
> >I now think our long time streamer load estimation of 1pF/foot + 220k
> >ohms (series) for a streamer load we use in models should have the
> >"1pF/foot" part replaced by:
> >
> >The capacitance in pF is:
> >
> >C = 0.0666667 x L        from 0 to 30 inchs
> >
> >C = 0.15 x L - 0.25     from 30 to ? inches
> >
> >L is in inches.
> >
> >It really does not change many things much, but there is a lot of
> >hard evidence to support that this is a "better" estimation that
> >agrees with HV leader folks, models, and testing...
>
>
> Hmmm..  While this empirically might work "better", I'm wondering what
> the physical basis is.
>
> Longer sparks will, in general, be created by a higher power source,
> which will have a larger Topload C, which will have higher currents,
> which will make a larger diamter spark channel, but I doubt that
> channel diameter has enough effect on C.
>
> More "furry offshoots" on longer streamers?
>
>
> Here's an experimental idea that might prove useful:
>
> 1) Take a given coil, and figure out a way to measure the C of the
> streamer (change in fres?) at sea level.
>
> 2) Take the same coil, run it in a low pressure environment (i.e. at
> 10000-15000 ft MSL (Drive to the top of Pike's Peak, or some high
> mountain resort), where the breakdown voltage is lower, and hence,
> with the same power input it should make longer sparks.  measure the C
> of the streamers.

Piecewise approximations do seem a bit suspicious. I suspect there is
a curve related to a "finger" area at the tip of the easily visible
streamers. I am reminded of the ball of barely visible streamers I
once saw emanating from a spherical topload with no defined spark
channel.

?
Malcolm