Grounded B Phase vs 3Phase 4Wire Systems

[396375HP]

What, if any, is the percentage of efficiency, plus or minus,of a 480 volt Grounded 'B' 3 phase 3 wire system as compared to a 277/480 volt 3 phase 4 wire system?

 

[davidbeach]

Efficiency defined as what? Obviously it uses only 75% as much conductor, so does that make it 133% as efficient?

 

[396375HP]

The question that was asked of me was,"Could I see any savings in my power usage,through better system efficiency, by changing from the Grounded B phase system to the 3Phase 4Wire system?

 

[davidbeach]

First order response, no.

Forth or fifth order response, yes. The power through the insulation admittances will be about half what it now is if you change. My guess is that any money spent to make the change will never be recovered through the savings achieved.

There are probably much better safety arguments to be made for making that change than operational efficiency.

 

[alehman]

Grounded B-phase system are generally considered antiquated and almost never installed these days. If you want a 3-wire grounded system, ground the neutral at the main switchboard and distribute with 3 wires from there.

 

[cranky108]

4 wire systems provide 277v for use in lighting circuits, without using a transformer. Provided the source is a wye.
Many small business find this useful.

3 wire systems use less copper wire and therefore cost less to install. Which is an advantage to companys that don't have 277v lighting load, and have greater distances to transmit the power (oil field is a good example).

 

[jghrist]

The only possible power usage differences would be the possibility that delta winding transformers may have different losses than wye winding transformers.

I assume that even though you reference a 4-wire 277/480 volt system, you wouldn't actually install a neutral unless it were needed. If it were needed, then the 3-wire 480 volt system would not work.

The difference in dielectric loss mentioned by davidbeach would not, at 480 volt, be enough to pay you for the time in asking the question.