Best EHV and EHT Insulator for a....Ridiculous...Project

[TJPMusic]

Hey folks, my first post here. Thanks for having me.

Okay- so...

I’ve began work on developing a prototype- it was an idea I had in a cold sweat in the middle of the night- I simply had to try it- and so far, my results are... encouraging. But, I’ve run into some design issues— and my experience with high voltage is limited, so I wanted to reach out for some expert advice.

Without revealing too much of the design, here’s what I need to make this happen:

I need an insulative material, the thinner the better, which has a dielectric strength of around...
a Megavolt...

...I know....... 

Heat strength is a must here, as well- but not as important as breakdown voltage.
Ideally, it should be able to be applied to a long, skinny cylinder, (picture a car antenna) and not need reapplication.

Anybody have any ideas? Am I dreaming? Does there exist such a material?

Anybody have any guesses for what I’m building? Let’s hear it!

Thanks for any help!

Cheers,

TJP

[Twospoons]

A megavolt per  what? Per metre? Per millimetre?  It makes a difference.

[johnf]

Cast perspex--not extruded is good
also pyrex glass is also good
both of these have known conduction measured in the G ohms so that the field is nice and gradual
other plastics / glasses have different  G ohms per unit length and do not work as well.
 try not to use materials in the tera ohm per meter range as they build up areas of uneven potential resulting in early flashover

[klugesmith]

Welcome!

Are you thinking of a paint-like coating, or a solid cylinder much larger outside than inside?  Where is the conductor whose potential is different by a megavolt from your "hot" conductor?

Twospoons hit the key point.
What counts is the electric field strength, in units like V/m or kV/mm.

For your long skinny cylinder, and "thick" insulator, the maximum E-field strength depends more on the cylinder's radius than on the distance to grounded conductor.

I think a good vacuum can withstand stronger E-fields, without breakdown, than any solid or liquid dielectric.