Re: buying a pole pig

["Tesla list" <tesla@xxxxxxxxxx>]

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

Three-phase voltage ratings are always phase-to-phase,
whether you're talking delta or wye.  That is why, for
wye, the "Y" voltage is higher ;-))  So it is
consistent, believe it or not.  It just so happens
that, in delta-connected three-phase, the phase
voltage and phase-to-phase voltage are the same thing.
 That's how I reason it out, at least.

AFAIK, wye is by far the most popular distribution
system in the U.S., and delta the most popular
transmission and sub-transmission system.  In
Washington State, everything 115kV or above seems to
be delta-connected.

Utilities pinch pennies a lot these days.  They don't
want to buy two-bushing pigs and then ground one
bushing (you can see that this is what was done in
Justin's pig pictures further up the thread).  Here
where I am (near Seattle), the only kind of pigs you
find are of the single-bushing sort, which can't be
delta connected without making the cans "hot".
Fortunately, conventional wisdom in pig coiling has
changed recently in favor of grounding one leg of the
HV from the pig, which means that all pigs are now
equal from a number-of-bushings perspective.

Regards,
Aaron, N7OE

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

> Original poster: "Gerry  Reynolds"
> <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi David,
>
> If the delta system was 12470 across two of the
> three phases, this
> would be identical to a Y system that had 7200V in
> each leg
> (referenced to ground) in that the voltage across
> two of its three
> phases would also be 12470V. Sounds like if the pig
> were hooked to
> 7200V across its 2 HV bushings and delivered 120Vac
> on the parallel
> LV configuration, then it would deliver 208 Vac in
> the same LV
> configuration when hooked across 12470V on the HV
> side. If one were
> to drive the LV with 240V in the parallel LV
> configuration, the
> output would be 14400V.  If the core can safety take
> the 12470/208
> without saturating then maybe there's hope for the
> 14400/240 operation.
>
> In terms of the sematics of the meaning of 12470Y,
> one could connect
> the pig across two phases of a Y system just as
> easily as a delta
> system so maybe this nomenclature is just fine.
> BTW, what is common
> in the USA, Y or delta or both??  With delta, the
> loads across each
> pair of phases needs to be balanced else the
> currents on one of the
> phases could be excessive.  In a Y system, any
> unbalanced currents
> are made up for by the ground path.
>
> Gerry R.
>
>
>
>
> >Original poster: DRIEBEN@xxxxxxxxxxxxxxx
> >Gerry,
> >