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Re: OLTC II Initial calculations



Original poster: "Jim Lux by way of Terry Fritz <teslalist@qwest.net>" <jimlux@earthlink.net>

At 07:46 AM 5/7/2003 -0600, you wrote:
>Original poster: "Stephen Conner by way of Terry Fritz 
><teslalist@qwest.net>" <steve@scopeboy.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.