Original poster: "Jack King" <ekklekktikk@xxxxxxxxxxx>
Adam - I wouldn't do it. Not, at least, before doing some more research on the particular unit. I recently found a GE JVT-200 PT. 200:1, 3kVA, two-bushing. It's positively enormous, as PTs go! Beyond hope, I actually got an original hardcopy manual with it when I picked it up. The manual specifically says *NOT* to ground one HV terminal unless operating at substantially reduced voltage. I forget the derating factor. It wasn't something obvious like 1/sqrt(2), though. It was even worse! I assume this is all because both sides of the HV are not insulated to 24kV (or better) from the core.
Hmmm - I wonder if they derate so much due to the risk of lightning strike or some other event that could push the envelope?...I know "our" applications are different, and have ltd duty cycles - the intended application remains connected 24/7 to hv.
I really dont see the harm in grounding the inner-most side of the HV winding...I almost see it as advantageous - - I would be real curious to hear the rationale at GE for not connecting this way...
Jack _________________________________________________________________From predictions to trailers, check out the MSN Entertainment Guide to the Academy Awards® http://movies.msn.com/movies/oscars2007/?icid=ncoscartagline1