Creepage distance? (was Re: 25 kV PT)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>

I just had another thought on this:  I wonder if the
GE-recommended derating has to do with creepage
distance on the *outside* of the transformer?  With
one bushing grounded, depending on the shape of the
PT, you may have just about halved the creepage
distance.  Obviously, this would be a major concern in
the wild, bad weather, etc., but in a nice dry garage,
it probably doesn't matter at all.

Anybody have any thoughts on *that* theory?

Where I live (near Seattle), I see two-bushing pigs on
the poles all the time with one ear grounded.  It's
not the general case, but fairly common.  I get the
feeling that most two-bushing pigs 15kV and lower are
good for delta or wye connections, and if you looked
in the can, you'd find the same exact transformer that
the factor also puts into a single-bushing can.

Regards,
Aaron, N7OE

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
>
> Bunnykiller's two 14.4 kV pigs aren't "center tapped
> transformers" either, yet he sucessfully overdrives
> them in series for 32 kV. My pig had one bushing
> grounded on the pole before I "liberated" it with a
> chainsaw. Are PT's less robust that pigs? My 25 KV
> PT's and my 14.4 kV pig all have BIL's of 125 kV.
>
> Adam
>