Spark Over Voltage

Short version:

Sparkover voltage is affected by a LOT of things: electrode shape, spacing,
air temperature, humidity, illumination (yes...).  Its not linear with gap
length. It falls as air pressure falls, then rises as a hard vacuum is reached.
It ALSO rises as air pressure is inreased.  When gaps are used for measurements
they are carefully calibrated.  HF/RF will jump larger gaps than the same DC of
60 Hz.


Dielectric Phenomena in High Voltage Engineneering
F W Peek

(STILL cited as a source.)

5 cm (?) spheres.  Spheres, anyway.

	0.1cm/0.0395"	1.0cm/0.395"

60 Hz	4.95KV		31.8KV
40KHz	3.65KV		28. KV

voltages are peak.

AC from a HF alternator.

Electrical Engineer's Handbook, Fink & Beatty

	1 cm, 31.4KV, peak

(which is close to Peek, above...)
(I remembered it as more like 25KVAC/Inch.  Live & learn...)

My impression is that natural lighting does not follow a mumble v/cm type
relation, but proceeds in rapid steps, a few 10s of meters per step, with the
hot channel statign ionized & low drop behind the leading point...