Step up Transformer grounding

[Georgietrotter]

When grounding a step up transformer (120 to 480 3 phase) can it grounded to the main grounding point or does it need to be a solo grounding point?

 

[ron]

All grounding electrode conductors get connected together. You can't have solo grounding electrodes. 250.50

 

[electrofelon]

Also see 250.30(A)(4) for specifics

 

[petersonra]

When grounding a step up transformer (120 to 480 3 phase) can it grounded to the main grounding point or does it need to be a solo grounding point?

Where are you going to get 120V 3 phase? Did you mean 208/120 is the primary?

In any case, you have to bring in an equipment grounding conductor with the incoming power. This EGC gets connected to the frame of the xfmr.

ONLY IF the secondary of the xfmr is a wye configuration, you would also have to run a grounding electrode conductor from the wye point to a nearby grounding electrode and the frame. Read the cited parts of the code other posters mentioned for further information. Otherwise it just connects to the frame.

 

[DrSparks]

Where are you going to get 120V 3 phase? Did you mean 208/120 is the primary?

In any case, you have to bring in an equipment grounding conductor with the incoming power. This EGC gets connected to the frame of the xfmr.

ONLY IF the secondary of the xfmr is a wye configuration, you would also have to run a grounding electrode conductor from the wye point to a nearby grounding electrode and the frame. Read the cited parts of the code other posters mentioned for further information. Otherwise it just connects to the frame.

You would also ground one of the phases if it is a Delta Corner grounded system

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[petersonra]

You would also ground one of the phases if it is a Delta Corner grounded system

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that is true but I cannot recall seeing a corner grounded system. they certainly exist but they are not especially common.

 

[kwired]

that is true but I cannot recall seeing a corner grounded system. they certainly exist but they are not especially common.

Grounding of them is the same, just to a different point.

Where they seem to be most common is reverse feeding a transformer that has a delta winding for it's "ordinary primary". With those you typically have no choice but ungrounded system or corner grounded system.