Re: Breakdown voltage in HV transmission lines (was: this was..)

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

Original poster: "Peter Terren" <pterren-at-iinet-dot-net.au> 

Antonio,  This has interesting implications for lifters which have a 'corona
wire'.  I have observed that the corona is only really evident at the
terminations of the balsa uprights or where there are kinks in the wire.
They also don't arc over in the mid section of the wire unless it is too
loose and flaps around too much.  I would expect that maximising corona
would improve lifting efficiency. It would be nice to have a wire with
conductive projections like fluff than a smooth straight albeit thin one.
Peter
http://tesladownunder.iinet-dot-net.au/

 >  > The cables do not appear to be very large in diameter --- perhaps an
inch or
 >  > two at best.  With that small radius and diameter, why don't they emit
 >  > tremendous corona?
 > The fundamental reason is because the wires are essentially straight.
 > Cylindric conductors donīt follow the same rule of spheres, where 30 kV
 > per cm of radius is enough to create corona.
 > If you try to calculate the electric field at the surface of a long
 > wire that is at a given potential, the result is that that if the wire
 > has infinite length and is really straight, the breakdown voltage is
 > infinite. But real wires are always somewhat curved by gravity....
 > Antonio Carlos M. de Queiroz