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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?

#131

Post by dredmorbius »

VBprogrammer wrote: post #112
dredmorbius wrote: post #90

Earlier quoted context omitted.

> Peter Fairley: So to give you a sense of just what the scale of the transfers is and how small it is, the East and the West interconnects have a total of about 950 gigawatts of power-generating capacity together. And they can share a little over one gigawatt of electricity. > Steven Cherry So barely one-tenth of one percent. From TFA.

I wonder if this has more to do with "Black Start" planning than actually providing power cross grids. https://en.wikipedia.org/wiki/Black_start

Interesting suggestion, though AFAIK that typically relies on auxiliary onsite power source at some generating plants, as noted in the Wikipedia article intro?

Anything you can find to support grid interconnects as black-start capacity?

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

#132

Post by heftig »

nemetroid wrote: post #42
nickff wrote: post #26

Earlier quoted context omitted.

Well, you have to consider that the USA (and Canada) were on the bleeding edge of technology when they adopted electrical grids. They were left with a... legacy, including the type-A plug and 110V single-phase power to residences. In your case, I believe each prong of your two-prong plug gets a different phase, so you have 3 possible pairs of phases to power each circuit from. This has the advantage of requiring smal…

No, one prong gets a phase and one prong gets the neutral, resulting in 230 V. Only equipment designed for 400 V gets two (or three) phases.

House-wide RCDs are also standard so if any current is not returned through neutral the circuit will be broken.

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

#133

Post by ssda2211 »

rob74 wrote: post #114

Always interesting to learn such details about infrastructure "hidden in plain sight". One more I can add is the separate traction power network in Germany, Austria in Switzerland, which is necessary because the railways here use a frequency of 16,7 Hz. It is fed in part by dedicated power plants (or dedicated generators in shared power plants), in part by converters. https://en.wikipedia.org/wiki/Traction_power_netw…

There is a wonderful YouTube channel called practical engineering. You might like that. It's primarily about hidden in plain plain infrastructure and the engineering behind it.

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

#134

Post by taneq »

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?

Pretty much. I mean, that's basically what a VSD is: A 3-phase rectifier back to back with a 3-phase inverter. Then you can have the two sides at different voltages and phases and transfer power back and forth at will.

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

#135

Post by gorbypark »

cm2187 wrote: post #92

The argument for more unified grids would have had more leg before the 2003 outage, where a failure was propagated through the grid and resulted in a blackout for a large part of the US. With multiple separate grids, at least you reduce the impact of such event.

It also took out a large chunk of mid eastern Canada (parts of Ontario and Quebec, iirc)!

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

#136

Post by VBprogrammer »

dredmorbius wrote: post #131
VBprogrammer wrote: post #112

Earlier quoted context omitted.

I wonder if this has more to do with "Black Start" planning than actually providing power cross grids. https://en.wikipedia.org/wiki/Black_start

Interesting suggestion, though AFAIK that typically relies on auxiliary onsite power source at some generating plants, as noted in the Wikipedia article intro? Anything you can find to support grid interconnects as black-start capacity?

Purely speculation based on the small capacity compared to total generated capacity.

From what I understand there can be a number of different techniques for black starting a grid, including pumped storage / hydro generation because they can be started with very modest power. Being able to jumpstart a grid based off of a neighbouring grid seems to make sense.

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

#137

Post by mwexler »

As I read this and started to see the politics rise up, I was reminded of a similar set of arguments and regs around electronic road toll collection. The US govt has mandated (the MAP-21 act of 2012) thst we move to a single standard so a sunpass from FL will work just like an EZpass from NY. Wired did a nice summary a few years ago on the lack of progress (https://www.wired.com/story/national-tolling-system/)

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

#138

Post by tonyarkles »

MrBuddyCasino wrote: post #124

Too much efficiency is dangerous: it makes the overall system more vulnerable because it removes redundancies, increasing systemic risk. Decision processes are not scale-invariant: politics, and therefore susceptibility to corruption, increases, transparency decreases. Not saying a unified grid is not worth it, but there are downsides that might not be immediately obvious.

I definitely picked up on the same thing, remembering the east coast blackout in 2003.

https://en.wikipedia.org/wiki/Northeast_blackout_of_2003

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

#139

Post by tonyarkles »

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…

Lots of good answers in the replies here, but one more thing to keep in mind is that, when the DC vs AC argument was going on in the late 1800s and early 1900s, we were still 40 years away from discovering semiconductors.

Nowadays, a lot of residential loads at least would probably be more efficient with DC coming into the house with the popularization off brushless DC motors and all the technology around the house.

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

#140

Post by kozak »

dredmorbius wrote: post #86
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…

Interesting explainer: Why 3 Phase Power? Why not 6 or 12? https://youtube.com/watch?v=HqZtptHnC2I (Substation complexity.)

I like the minimalistic explanation that it's because two phases are not enough and four phases are too many.
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