when is transformer grounded like a service? I mean, when would you have a double barrel lug on xo with both a ground and nuetral terminated on it.
Transformers in electrical rooms I've worked on (eg:90kva) 480/277 stepdown to 208/120 did not have the ground tie in with the neutral. However, I've seen temp skids and certain roof top transformers with had the ground go through a grounding bushing then to the frame of the trans. and then up to the neutral terminal (xo) along with the nuetral.
Is this done if lighting strike are a concern?like on a roof? or an outdoor temp skid. service ground VS equipment ground.
