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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?

#61

Post by na85 »

ClumsyPilot wrote: post #20
na85 wrote: post #11

Earlier quoted context omitted.

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.

I agree. To say that a natually-occurring physical process or phenomenon was invented is nonsensical.

Electricity is not the same as electric power, just as nuclear fission is not the same as a nuclear weapon, just the same as fire is not the same as a coal fired power plant.

Electricity and nuclear fission were discovered, not invented.

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

#62

Post by marcosdumay »

swatson741 wrote: post #55

The article makes this seem like it's a US problem but, the interconnects lay in Canada and Mexico too. I'm guessing that unification is a low priority for them since it seems that the US stands to gain the most from it. "DC power lines transmit power more efficiently than AC lines do" This is not at all what is taught at school. Looking into this is interesting. 100 years ago people were debating about whether AC or…

HVDC is much better than anything else for long distance transmission. But the gain is because of the high voltage part, not the DC one.

The one thing that pushes people into DC is that phase synchronization is a huge problem on high voltage. So, for indirect reasons, DC gets to be the winner right now.

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

#63

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

I come up with a hypothesis: Japan's divided frequency situation made Japanese electric manufacturers to invent inverter for electrics (example: air conditioners, microwave, refrigerators). Inverter primary makes electrics controllable efficiently, also they can ship same product (same performance) for both 50/60Hz area in Japan.

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

#64

Post by fireattack »

fomine3 wrote: post #63
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

I come up with a hypothesis: Japan's divided frequency situation made Japanese electric manufacturers to invent inverter for electrics (example: air conditioners, microwave, refrigerators). Inverter primary makes electrics controllable efficiently, also they can ship same product (same performance) for both 50/60Hz area in Japan.

Any "evidence" (or anything substantial) about your hypothesis?

Like, did Japanese companies actually invent inverters, or are inverter air conditioners more common in Japan compared to other countries?

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

#65

Post by fomine3 »

fireattack wrote: post #64
fomine3 wrote: post #63

Earlier quoted context omitted.

I come up with a hypothesis: Japan's divided frequency situation made Japanese electric manufacturers to invent inverter for electrics (example: air conditioners, microwave, refrigerators). Inverter primary makes electrics controllable efficiently, also they can ship same product (same performance) for both 50/60Hz area in Japan.

Any "evidence" (or anything substantial) about your hypothesis? Like, did Japanese companies actually invent inverters, or are inverter air conditioners more common in Japan compared to other countries?

Sorry for bad English, "develop" would be better word than "invent". AFAIK Daikin argues that Inverter Air conditioner is very popular in Japan compared to other developed countries. In Japan, mini-split type a/c is common and almost all producs are runned by inverter compressor (except very cheap one but almost no one buy it).

Here's Daikin's argument (japanese). Green is % of inverter and Japan is 100%.

https://www.daikin.co.jp/csr/information/lecture/act01.html

https://www.daikin.co.jp/csr/information/lecture/images/act0...

It seems that world's first inverter a/c is by Toshiba.

https://toshiba-mirai-kagakukan.jp/en/learn/history/ichigoki...

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

#66

Post by djsjbsjd »

swatson741 wrote: post #55

The article makes this seem like it's a US problem but, the interconnects lay in Canada and Mexico too. I'm guessing that unification is a low priority for them since it seems that the US stands to gain the most from it. "DC power lines transmit power more efficiently than AC lines do" This is not at all what is taught at school. Looking into this is interesting. 100 years ago people were debating about whether AC or…

To transmit power without loss you have to increase the voltage. The easiest way to do this (And in the late 19th century the only way) is with a transformer, and therefore AC.

However, since the 1930s we’ve been able to build high voltage DC lines, and costs have plummet in the last 30-40 years (as we moved away from Hg rectifier tubes to Si high power electronics).

DC has many advantages:

- No capacitive coupling to ground - No reflections due to Z mismatch - You can lay a cable underwater (basically impossible with AC) - you can connect incompatible grids

HVDC is still fairly expensive (obviously compared to a lump of laminated steel) so it’s used for very long lines, or other special needs.

But it’s revolutionized the field.

AC still has many advantages and won’t go anywhere, especially last-mile to medium range:

- arguably safer since an arc fault can self extinguish - switches are much cheaper to build - cheap electric motors - cheap ability to scale V

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

#67

Post by djsjbsjd »

marcosdumay wrote: post #62
swatson741 wrote: post #55

The article makes this seem like it's a US problem but, the interconnects lay in Canada and Mexico too. I'm guessing that unification is a low priority for them since it seems that the US stands to gain the most from it. "DC power lines transmit power more efficiently than AC lines do" This is not at all what is taught at school. Looking into this is interesting. 100 years ago people were debating about whether AC or…

HVDC is much better than anything else for long distance transmission. But the gain is because of the high voltage part, not the DC one. The one thing that pushes people into DC is that phase synchronization is a huge problem on high voltage. So, for indirect reasons, DC gets to be the winner right now.

“But the gain is because of the high voltage part, not the DC one.“

What do you mean by that? My understanding is the HVDC lines are still lower V than an AC line (the Soviet even had 500lV lines), and therefore DCs advantages are no coupling to ground, no Z reflections and ability to connect to any grid.

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

#68

Post by jdswain »

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?

Wouldn't a better solution be to make them all in phase with each other? Then there wouldn't need to be any HVDC interconnect.

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

#69

Post by X6S1x6Okd1st »

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.

Do you think that electricity can credibly be called an invention?

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

#70

Post by crmrc114 »

labcomputer wrote: post #34
crmrc114 wrote: post #14

Earlier quoted context omitted.

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 numbe…

> Close, Three phase systems actually are a carry over from the days of early induction motors. It's not just some historical accident. We continue to use multi-phase power because it enables continuous delivery of power (unlike single-phase, where the delivered power drops to zero at least twice per cycle). And two phases require just as many wires as three phases, with more power delivered for a given mass of coppe…

If both loads were on the same phase that would be a violation of the US NEC (NFPA 70) because use the load would be 40 amps..... And guessing we are taking 12awg, way over allowed current.

In hindsight I did not specify circut ampacity, or wire gauge. Still the question stands, how much current would you read at the panel on the neutral with those two loads on the line :-)

(In my example you have two phases 120 degrees apart. Think US Residential split phase. The actual result is pretty awesome. It's a common test problem for new electricians.)

I won't spoil the result because it's too cool when you get it.

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