National Grid Grounding Transformer Guidelines

[Izverg]

Hi guys,

I am working on a solar project in NY, where we are interconnecting solar plants into National Grid.

I do have the CESIR studies, and they mention a need of a zig zag transformer, but the math does not make full sense to me. I tried to find their guidelines on how to size it properly but could find anything.

Anybody could point out to a specific document on where this is explained?

Thank you!

 

[mbrooke]

Would this help?

Edit: re-reading your post the doc may not help- but I still want to ask- what is forcing a zig-zag?

 

[Izverg]

Thank you so much for the quick reply, unfortunately not. This is not what I am looking for.

This is an example from a different utility (Xcel):

https://www.xcelenergy.com/staticfiles/xe/PDF/MN-SRC-Invertor-Based-Ground-Refrencing-Requirements-and-Sample-Calculations.pdf

What I am looking for is the requirements of the grounding transformer as shown in the example on page 2.

 

[mbrooke]

Thank you so much for the quick reply, unfortunately not. This is not what I am looking for.

This is an example from a different utility (Xcel):

https://www.xcelenergy.com/staticfiles/xe/PDF/MN-SRC-Invertor-Based-Ground-Refrencing-Requirements-and-Sample-Calculations.pdf

What I am looking for is the requirements of the grounding transformer as shown in the example on page 2.

If the inverter has a zero sequence source, I can't see the zig zag being needed?