Transformer grounding question

[wwhitney]

Specifically what I would really appreciate is if someone could advise me on what I need to do with the grounding on the primary side of the transformer which I can take to 250.30 and see how it conforms rather than asking me to read 250.30 and figure it out for myself. If you tell me the what I can figure out the why.

Is the above a typo? Your question would make more sense if it were secondary, so this post assumes that is what you meant.

For the secondary side, does the image in post #5 suffice? The "ground" symbol there is a grounding electrode that is already part of the building GES, and the orange line is the GEC for the secondary side. I.e. it's the "ground rod" you referred to, but it's not an isolated ground rod, it's part of the existing interconnected GES.

How far is the transformer physically going to be from the building service? Is the 480/277V panel supplying it the service panel?

I'm not a 250.30 expert and I've never physically touched a power transformer, but the basic idea is that on the secondary side you need a system bonding jumper connecting X0 to the secondary side EGC, to provide a fault return path. And then since apparently earthing is considered important, you provide a direct attachment to the building GES at the transformer secondary, rather than relying on the existing connection path that you get via the primary/secondary EGC connection and the GEC on the primary side.

Cheers, Wayne

 

[petersonra]

If you are NOT trying to use the EGC with the feeder also as the grounding electrode conductor, then I don't think there's anything else to think about other than a quick glance at table 250.122.

He will still need a sbj.

 

[electrofelon]

He will still need a sbj.

Right, but my understanding was he was just concerned with the details of the EGC with the primary conductors.