Another transformer question neutral, from primary to secondary?

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rick711

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I am confused about what I read in my old book about transformers, "a neutral conductor, if required, is carried
from the primary, through the transformer, to the secondary". There is a picture of a transformer with the wiring
shown and visible are the primary terminals marked H1, H2, H3, with conductors brown, orange, yellow then toward
the middle you see a conductor with a white tape on it and its terminal has a bar of metal between/from itself and
the next terminal that has another conductor on it also with white tape. This is what I do not understand, the book
does not show a schematic but it looks like the neutral is coming in with the 480 VAC (as the book stated) and is
on a terminal that is connected or bonded with the terminal for the neutral for the output side. Would this mean
that the primary and secondary are no longer separated, I read out of this old book and the primary and secondary
are separated and use "mutual induction" to transfer electrical energy/step up or down, but they are separated
electrically. I am learning a little at a time. If anyone can help it would be appreciated. I do not have anyway of
scanning or attaching a picture of this book it was free, old half missing.
 
The "ground" (forgive me using that word) on the 480v side should be an equipment grounding conductor to the transformer case to address primary faults. It should meet 250.119 as far as color (green). The output side neutral will often have a system bonding jumper connecting XO to the transformer case 250.30(A). The fact that both primary and secondary are connected thru this grounding requirement is unavoidable and the transformer is still considered a separately derived system.
 
Another possibility is that this "old book" was showing an installation of a transformer not as an SDS. I.e. connecting a neutral in the primary feeder to the secondary neutral, and using an EGC run with the primary to bond the case and provide the secondary EGC. With no other neutral-ground bonds--the secondary system relies on the neutral-ground bond present on the primary side.

I understand the SDS installation is far more common, but I don't understand all the pros and cons vs the above. One plus for the SDS is that the fault clearing path on the secondary side is shorter.

Cheers, Wayne
 
I am sorry, I just saw that the response I wrote is not posted, I think that I did not hit "return"
or post, in a nutshell my phone camera has not worked in a long time and I do not have a
scanner or printer. I will try and figure out something.
 
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