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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.