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Re: 25 kV PT



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

I'm still not sure what you mean by "Neither H1 or H2 may necessarily be closer to ground"

From what you say below, it sounds like H2 is physically closer to the core and would be the best candidate to ground for a PDT. Question then is what about PTs??

Gerry R



Original poster: "Dr.Hankenstein" <Dr.Hankenstein@xxxxxxxxxxxxx>

Neither H1 or H2 may necessarily be closer to ground. Let me explain:

When one winds a transformer, the begining of the winding is refered to as
"start". When you are done, that's the "finish". While the transformer is
being tested, such as with a TTR set (transformer turns ratio test set) the
polarity marks are commonly refered to as "start and finish" and the test
set's connections are called "polarity and non-polarity", not H1, H2 to X1,
X2, etc.

Now, with the above in mind, a normal "pole" transformer would have the H2
connected to the "start" of the winding, and the H1 connected to the end or
"finish" of the winding. Being that the "finish" or H1 is furthest away
from the core, you really don't want to ground that end! The "finish" is
only called "H1" for connection's sake, and it is an industry standard so
even a Lineman Apprentice can properly hook-up and phase in a transformer
bank,... just by looking at the pictures. (No offense to the Linemen out
there, because if it wasn't for the pictures, I probably couln't do it
either.

If you still confused, use a single-bushing transformer. Then there's
absolutely no doubt which end is grounded!