12.47kv overhead line

[lilsparky]

Ok here's today's question: there's a 12.47kv overhead line that feeds into a 500 kva 12.47kv - 480v outdoor transformer which feeds two facilities. Now we are upgrading this facility and adding in a fire suppression system that has to have it's own separate reliable power. I need to tap off the 12.47kv line at the pole to feed another 12.47kv - 480v transformer, however I only see 2 phases on the pole being brought down to the existing transformer. Is that correct? can I still tap this line?

 

[steve66]

Are you installing a fire pump??

Where is the service point where the utility ends and the facilities electrical begins? (Or is this a campus type arrangement)?

I'm not sure why you would have to go back to the primary.

 

[bob]

IMO the 500 kva transformer is too large to be connected to only 2 phases. I would go back
and find the 3rd phase and bring it to your tap point. As far as the fire pump, if the transformers
are not too large you can use only 2 phases and connect the transformer open delta.

 

[Tom Sawyer]

PGE 1303E Rule 2 Part D General Load Limitations

PGE 1303E Rule 2 Part D General Load Limitations

"Single Phase Service Part a) "For any single-phase service, the maxiumum demand as determined by PG&E is limited to the capacity of a 100 KVA transformer unless otherwise approved by PG&E. If the service is greater than 100 KVA, the service normally would be three-phase." This is to keep large single-phase (line to line) demands from imbalancing their 12KV lines.