RE: negative streamer propagation?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "J. Casey Crager" <jccrager-at-bu.edu> 



Bert,

Thanks a lot for the references.  I'll check them out today.  I'll let
you know if I find others.

Thanks again,

Casey


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, January 27, 2004 12:51 AM
To: tesla-at-pupman-dot-com
Subject: Re: negative streamer propagation?

Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net>

Tesla list wrote:
 >Original poster: "J. Casey Crager" <jccrager-at-bu.edu>
 >Are there any quantitative explanations based on theory why you need
 >higher voltages for negative streamer propagation?
 >
 >Thanks,
 >Casey

Hi Casey,

Most literature tends to focus on positive leader propagation since this

polarity is the most troublesome for air insulated high voltage systems
due
to the lower breakdown voltage. There is a wealth of experimental data
for
both positive and negative rod-plane gaps, and a number of detailed
computer models for positive leader propagation. Positive leader
propagation is considerably simpler to model, since streamer and leader
propagation head only toward the cathode.

In negative leader propagation, streamers and leaders may propagate in
BOTH
directions from partially ionized regions inside the gap (called space
or
plasma stems) which behave as "fictitious electrodes" floating within
the
gap. Much of the work in negative leader propagation has been driven (at
a
macro level) by lightning research and modeling. Because of the added
complexities, models for negative leader propagation are scarce, tending
to
be macro models for lightning propagation. Most papers simply refer to
the
leader process, assuming that the reader understands that they mean
positive, cathode-directed streamers and leaders.

Since you have an "edu" email address, you probably have easy access to
the
scientific literature. Following are a few references that that discuss
leader propagation theory, negative leader propagation, and the
differences:

"An experimental study of negative discharge in a 1.3 m point-plane air
gap: the function of the space stem in the propagation mechanism", T
Reess,
P Ortega, A Gibert, P Domens and P Pignolet, J. Phys. D: Appl. Phys. 28
(1995) 2306-2313

"Performance of a 16.7 m air rod-plane gap under a negative switching
impulse", P Ortega, P Domens, A Gibert, B Hutzler, and G Riquel, J.
Phys.
D: Appl. Phys. 27 No 11 (14 November 1994) pp 2379-2387

"Self-similar properties of minimum sparkover voltage in air for both
polarities in rod-plane (0.1-30 m) gaps", M M Kekez, J. Phys. D: Appl.
Phys. 18 No 9 (14 September 1985) pp 1813-1823

"The Lightning Flash", Vernon Cooray (editor), IEE Power and Energy
Series,
ISBN 0852967802 - see section 3.15.2 General charateristics of impulse
breakdown in rod-plane gaps, pp 114-123.

"Spark Discharge", E. M. Bazalyan, Yu. P. Raizer, CRC Press, 1997, ISBN
0849328683 - See Chapter 6 (The Leader Process) for quantitative
discussion
of positive leader mechanism, and section 6.11.1 (A Negative Leader),
pages
353 - 256 for qualitative discussion of why long gap breakdown threshold

for negative discharges is significantly higher than for positive
discharges.

Good luck and happy hunting! And if you find some better papers on
this  subject, please let me know.

-- Bert --
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