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Re: Setting up a pole pig's wiring

Original poster: FIFTYGUY@xxxxxxx In a message dated 5/1/06 12:37:55 PM Eastern Daylight Time, tesla@xxxxxxxxxx writes:

>Yes, but there is no assumption. D.C. said "as the interior side of
>primary is at X1 (grounded) potential". That indicates, connecting X1
>to ground. That is clear.

Sorry, I'm a little slow, but that still doesn't clarify it to me. If anything, this raises the additional issue of which end of the *primary* winding is adjacent to the core or secondary winding. Again, unless I'm missing some conventional labelling of pole pigs, the worst case could end up:

One end of primary (LV winding), the end furthest from core, at ground potential Other end of primary (LV winding), the end closest to core or to the secondary's (HV winding) HV end, at 240V One end of secondary (HV winding), the end furthest from core, at ground potential Other end of secondary (HV winding), the end closest to the core or to the primary's (LV winding) 240V end, at 15kV

Obviously this is the highest-stress situation, and best-case is the complete opposite. My concern is calling the "H1" or "X1" labelled ends of the windings the ones closest to the core or other winding. Is there some convention that pig manufactures must follow when labelling, or should a pig owner open and verify the connections?

>I would however clarify ground as RF ground.

    Thank you for that clarification.

>I've been running this connection on my pig ever since David
>discussed with me a few years ago.

    Glad to see it's stood the test of time!

>This is not something that can be done with an NST system where the
>hv winding is center-tap grounded. But, with a depotted NST, the
>center-tap to ground connection can then be removed and run the same
>way to minimize pri to sec stress.

On an (9, 12, or 15kV) NST, the interior ends of both HV windings are both grounded to the core. Grounding one "bushing end" puts 4.5, 6, or 7.5kV stress at the center of the HV windings to core, where there was zero stress before. If the depotted NST HV winding fails, and the core isn't still grounded, that puts the core floating at 4.5 - 7.5kV where it normally would be at ground. And thus it would put an abnormal stress to the primary winding adjacent to the core. So in that respect I don't think that connection scheme minimizes primary to secondary stress.

-Phil LaBudde
-Phil LaBudde