what is the three phase power in my neighborhood?

Question

I live in a city and well, its been awhile since I have been in school, but does anyone know what the 3 phase power is that sits ontop of the powerpole? Whether its delta or Y, How much volts to ground and between each legs?

They use this power to energize the transformers that provide 240/120 to residential customers. Thanks for all the help.

Answer 1

Depends. In the US, a typical utility three phase distribution system these days has line to line voltages ranging from 12.5kV to 34.5kV. They are generally multiple grounded Y systems, with line to ground voltages between 7.2kV and 19.9kV.

These voltages must of course be stepped down to serve the customer. The stepdown transformers may be connected wye or delta depending on the applicaton.

Hope this helps!

-jtd

P.S. Just read Thomas answer. Pretty good. He knows what he is talking about.

Answer 2

Distribution voltages in the US can range from 4 kV up to 34 kV. Depending on where you live, it could be anywhere in that range.

If you update your question with a major city, we can probably provide an educated guess. A good clear photo of a distribution pole will allow the trained eye to estimate the primary voltage. We know the subtle differences in size of insulators, number of skirts, physical attributes of components, etc.)

As for whether it is wye or delta, that also depends on the distribution system. While the majority of the US uses wye distribution circuits, I know of a major Michigan city that still uses an 11 kV delta system.

In general, the three phase conductors will be up near the top of the pole on a wood arm. The neutral conductor for a 4-wire wye system is mounted to the pole a few feet lower. But still above the telephone and cable TV.

To determine if the system serving you is a wye or delta circuit, look at the transformer serving your home. If there is only one cutout (a.k.a. fuse holder) then the transformer is connected phase-to-ground and you have a wye circuit. If there are two cutouts, then the primary winding is connected phase-to-phase and you are likely on a delta circuit.

Some utilities with a wye system purchase their pole top transformers with only one primary bushing. That would also be a tip off that you are on a wye circuit. However the converse is not true -- Some companies purchase transformers with two primary bushings for their wye circuits. You can not immediately conclude that a transformer with two primary bushings is connected to a delta circuit.

Answer 3

It depends on where you live. 2 common voltages are 13.2kV and 4.16kV. 3 phase voltages are always stated in their phase to phase voltage. The phase to neutral is found by dividing the phase to phase voltage by the square root of 3.

The secondary of the transformer supplying the lines will be Wye.

You will notice there are often 4 wires because it reduces transformer costs to power the 240/120v transformers at, the lower, phase to neutral voltage.

Answer 4

The Delta and Y are related to the internal wiring of electric generaters and motors,

Grid input
At the generating plants the energy is produced at a relatively low voltage of up to 30 kV (Grigsby, 2001, p. 4-4), then stepped up by the power station transformer to a higher voltage (115 kV to 765 kV AC, ± 250-500 kV DC, varying by country) for transmission over long distances to grid exit points (substations).

Grid exit
At the substations, transformers are again used to step the voltage down to a lower voltage for distribution to commercial and residential users. This distribution is accomplished with a combination of sub-transmission (33 kV to 115 kV, varying by country and customer requirements) and distribution (3.3 to 25 kV). Finally, at the point of use, the energy is transformed to low voltage (100 to 600 V, varying by country and customer requirements).

Answer 5

usually Y, usually 12kV
Since its Y, Vp *3^(1/2) = V(line-line)