Re: electric strength for "x" cm of "y" material

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Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>

Hello Antonio.

> Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

> So, if there is some corona
> between two conductors, placing an insulating plate between them
> can only increase the corona. In other hand, a possible solution
> is to place dielectric plates behind the conductors, not between
> them.

solution of what?

imagine the voltage between the primary & secondary is 100kv, the
distance - 2.5cm, field is homogeneous. at the beginning there`s no
corona - the field strength makes the air breakdown at once.
so i replace (the bigger) part of the air to the LDPE - 2cm of plastic.
if designate dielectric constant as "e", relative length of the insulating
interval (relation of the interval lenght to the distance  between the
electrodes) as "L", voltage on the electrodes as "U", then:

Eair = e*U/(e*Lair + Lldpe)

so - in my case the field stress in the air gap will increase in 1.825
times and would be equal to 73kv/cm - right?
now i would have a corona - it would take all these 5mm of air volume,
or it would be concentrated near the surface of my copper primary?
if near the copper pipe - no problem, if only the polyethylene is not
gets too hot. and what about replacing the whole LDPE sheet with roll,
as D. C. Cox said - "wrap the inside of the lower part of the tube
with 10-12 layers of 20 mil polypropylene"? then the corona would
occur between every layer and the neighbor one, so - all this roll
would shine from inside? :-)))
and if we`d take a dc source, 2 electrodes, tight 2 sheets of plastic
to the each electrode, having left the air gap between them - would
the air be shining? it must be cool - air breakdown without dielectric
breakdown, what - dc current through the dielectric? :-)