Re: OLTC II Initial calculations

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

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 07:46 AM 5/7/2003 -0600, you wrote:
>Original poster: "Stephen Conner by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
>
>OK, so I have John Freau telling me that 60" sparks from a 24" tall 
>secondary is fine,


The Freau equation relates power input to spark length.  Clearly, a 60" 
spark from a 24" tall secondary is a highly nonuniform field (since the 
spark is a LOT longer than the breakdown distance along the coil) and other 
things are at work than a bulk breakdown phenomena.




>and Malcolm Watts telling me that a safe maximum voltage gradient is 8ft 
>per megavolt.


This is basically the inch per 10 kV design clearance guideline... 96 
inches -> 960 kV.. A handy rule of thumb when designing HV equipment.


The breakdown in a uniform field is around 70 kV/inch, so the 10 kV/inch 
covers things like relatively small conductor diameters, and so forth, 
insuring that corona losses will bite you before flashovers do.