45 kv transformer

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sully155

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On a stepdown transformer from 277/480 to 120/208 do the neutrals and grounds go together or is the low voltage panel considered a sub panel?
 
The transformer is the first component in a new "Separately Derived System." As such, neutrals and grounds are bonded at the first downstream enclosure that has the first disconnecting means associated with this new SDS. So the answers are yes, and no, in that order.

Welcome to the forum.
 
The bonding jumper between the XO and the EGC can be either at the transformer or at, in this case, the panel. Does the panel contain a main CB?
 
45 kv transformer

Yes the panel does contain a main cb. the big problem is that we are having voltage coming back on the ground and it is tripping the main gfi in the 2000 amp switchgear there are many panels in the building and if these panels are wired wrong I need to look into this more.
 
sully155 said:
Yes the panel does contain a main cb. the big problem is that we are having voltage coming back on the ground and it is tripping the main gfi in the 2000 amp switchgear there are many panels in the building and if these panels are wired wrong I need to look into this more.
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Can you describe the layout in more detail?
 
They may or may not be wired wrong, depending upon which code cyc they were installed under
 
sully155 said:
Yes the panel does contain a main cb. the big problem is that we are having voltage coming back on the ground and it is tripping the main gfi in the 2000 amp switchgear there are many panels in the building and if these panels are wired wrong I need to look into this more.
Click to expand...

what is the setting on the main ground fault ??
 
Sully,

What do you mean by ' do the neutral(s) and ground(s) go together ? Also, The feed to

the transformer, is it 277/480 3ph 4wire or is it 480v 3ph 3 wire? Are these the N & GRDs

refered to ? The feed should only be 3ph with no neutral.
 
Did you pull a neutral into this transformer from the primary/high voltage/input side?

This is just about the one way for this to happen OR

There is a 277 VAC circuit tied into a 208/120 VAC panel (back fed), when you energize the transformer you are bucking and tripping the GFP.


Also the transformer IS NOT 277/480 it is a delta connection and is 480 VAC while this is a minor point proper terminology is important in any profession.
 
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