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Why Does the U.S. Have Three Electrical Grids?

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Re: Why Does the U.S. Have Three Electrical Grids?

#11

Post by na85 »

X6S1x6Okd1st wrote: post #10

> If you look at lists of the 100 greatest inventions of all time, electricity figures prominently. Once you get past some key enablers that can’t really be called inventions—fire, money, the wheel, calendars, the alphabet Well that's a doozy of a way to start. How is electricity an invention but those listed after are not?

Fire is a natural phenomenon and I don't see how it can credibly be called an invention. That would be like calling water an invention.

The others, though, are certainly inventions.

Re: Why Does the U.S. Have Three Electrical Grids?

#12

Post by iaw »

na85 wrote: post #11
X6S1x6Okd1st wrote: post #10

> If you look at lists of the 100 greatest inventions of all time, electricity figures prominently. Once you get past some key enablers that can’t really be called inventions—fire, money, the wheel, calendars, the alphabet Well that's a doozy of a way to start. How is electricity an invention but those listed after are not?

Fire is a natural phenomenon and I don't see how it can credibly be called an invention. That would be like calling water an invention. The others, though, are certainly inventions.

I would argue that the ability to make controlled fires was an invention and perhaps the first chemistry humans intentionally performed, but I think it's just a point of semantics.

Re: Why Does the U.S. Have Three Electrical Grids?

#13

Post by msisk6 »

aidenn0 wrote: post #5
Pfhreak wrote: post #4

> Everything within those separate zones is synched up. So you’ve got your 60 hertz AC wave; 60 times a second the AC power flow is changing direction. And all of the generators, all of the power consumption within each zone is doing that synchronously. But the east is doing it on its own. The West is on a different phase. Same for Texas. Folks may not realize that power is transmitted in three phases in the US. AC p…

The solution is to connect them with HVDC, right? That might not be a great solution for making a single national-grid, but it would allow the 3 grids to mutually borrow from each other, right?

That's exactly right, but the capacity is limited. ERCOT in Texas, for example, has 5 DC ties to the other grids: http://www.ercot.com/content/cdr/html/real_time_system_condi...

Re: Why Does the U.S. Have Three Electrical Grids?

#14

Post by crmrc114 »

Pfhreak wrote: post #4

> Everything within those separate zones is synched up. So you’ve got your 60 hertz AC wave; 60 times a second the AC power flow is changing direction. And all of the generators, all of the power consumption within each zone is doing that synchronously. But the east is doing it on its own. The West is on a different phase. Same for Texas. Folks may not realize that power is transmitted in three phases in the US. AC p…

Close, Three phase systems actually are a carry over from the days of early induction motors. Three phases can easily be connected to create a rotating magnetic field. We don't just use one phase at a time on the grid. All three are active. Phases A and B and C are all 120 degrees out of phase with each other. (That has nothing to do with the 120volts you know of in your house- it just happens to be another 120 number)

AC has inductive properties. I.e. it can induce electrical currents in wires across a core. (Transformer) DC cannot do this. Before vacuum tubes and other tech AC was one of the few technologies that could be easily stepped up to hundreds of thousands of volts.

Voltage and current have an inverse relationship. So we can step up voltage and reduce the size of the conductor $$$$ other feature is reduced line losses (HVDC actually beats us here but this is another discussion)

Having AC power allows all kinds of cool things! Did you know that your common household 120v feed is simply a single phase being split into two 120v 'legs'. Both 120 degrees out of phase. So if you remember elementary school math the abs() of phase A at its peak of +120 and phase B at it's valley of -120 = 240.

It gets better! We can be cheap on wire with AC systems! I can wire a 'multiwire branch circuit'. With phases a and b that share a neutral. If the current on phase a is 20 amps and the current on phase B is 20 amps what is the return current on my neutral? ( Google Mike Holt Multiwire Branch, Enjoy )

Want more fun. Read about Neutral Earth Voltage and NFPA 70 requirements for agriculture and equipotential planes. :-)

AC is freaking magical. The grid is even more awesome!

Re: Why Does the U.S. Have Three Electrical Grids?

#15

Post by hristov »

Pfhreak wrote: post #4

> Everything within those separate zones is synched up. So you’ve got your 60 hertz AC wave; 60 times a second the AC power flow is changing direction. And all of the generators, all of the power consumption within each zone is doing that synchronously. But the east is doing it on its own. The West is on a different phase. Same for Texas. Folks may not realize that power is transmitted in three phases in the US. AC p…

I am not sure what your point is. It is possible to change the phase of a signal. In fact, a simple capacitor or inductor will do it.

With high power systems it might not be practical to do it with a single capacitor or inductor but it still can be done.

Re: Why Does the U.S. Have Three Electrical Grids?

#16

Post by lutorm »

nickff wrote: post #6
Pfhreak wrote: post #4

> Everything within those separate zones is synched up. So you’ve got your 60 hertz AC wave; 60 times a second the AC power flow is changing direction. And all of the generators, all of the power consumption within each zone is doing that synchronously. But the east is doing it on its own. The West is on a different phase. Same for Texas. Folks may not realize that power is transmitted in three phases in the US. AC p…

>"[W]e basically always have at least one phase providing power at any time." This isn't really how three-phase power works. In household settings, you're usually getting only one phase, so all your power comes from that phase. Different neighborhoods get different phases, so they're roughly balanced loads. Industrial (and some consumer) users get two (208V) or three phases (480V), and they get power from the differe…

At least in Sweden, all houses have a 3-phase, 400V supply. This is very different from the US which just supplies one phase to each house even if the supply itself is 3-phase. This is why you commonly see 200+A main breakers on a house in the US whereas in Sweden, 25A is a pretty common main breaker size.

(It's as if the US grid characteristics were decided by the copper vendors... ;-)

Re: Why Does the U.S. Have Three Electrical Grids?

#17

Post by SECProto »

na85 wrote: post #11
X6S1x6Okd1st wrote: post #10

> If you look at lists of the 100 greatest inventions of all time, electricity figures prominently. Once you get past some key enablers that can’t really be called inventions—fire, money, the wheel, calendars, the alphabet Well that's a doozy of a way to start. How is electricity an invention but those listed after are not?

Fire is a natural phenomenon and I don't see how it can credibly be called an invention. That would be like calling water an invention. The others, though, are certainly inventions.

I see a lot more natural electricity (lightning, monthly) than I do natural fire (wildfires? Never)

Re: Why Does the U.S. Have Three Electrical Grids?

#18

Post by fomine3 »

nickff wrote: post #3

The most interesting national electricity grid has to be Japan's, with two completely different networks operating at different frequencies, and connected by HVDC. https://en.wikipedia.org/wiki/Electricity_sector_in_Japan

That's still pain. When I (live in 50Hz area) buy cheap dehumidifier, I get lower performance due to lower frequency.

Re: Why Does the U.S. Have Three Electrical Grids?

#19

Post by hristov »

Ugh, another way the Trump administration is holding back the country. The frustrating thing is this time the scientists almost got away with it. If they just did not invite any political DOE officials to their presentation, they might have published the paper.

Re: Why Does the U.S. Have Three Electrical Grids?

#20

Post by ClumsyPilot »

na85 wrote: post #11
X6S1x6Okd1st wrote: post #10

> If you look at lists of the 100 greatest inventions of all time, electricity figures prominently. Once you get past some key enablers that can’t really be called inventions—fire, money, the wheel, calendars, the alphabet Well that's a doozy of a way to start. How is electricity an invention but those listed after are not?

Fire is a natural phenomenon and I don't see how it can credibly be called an invention. That would be like calling water an invention. The others, though, are certainly inventions.

Well, by that logic neither is electricity, since lightning exists.

And magnets certainly do occur naturaly, and so does nuclear fission and fusion.

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