Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

spectrum.ieee.org

Post reply on HN
Print view View original

101–110 of 155 posts

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

#101

Post by danw1979 »

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

"The total transmission capacity between the two grids is 1.2 GW"

That's a tiny amount for an industrialised nation of 125 million people, considering that the border between the grids cuts right between Tokyo and the other western centres of population.

I think this, and the nuclear power shutdown, lend some context to Japan’s push for a hydrogen economy.

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

#102

Post by ew6082 »

ggm wrote: post #2

Australia is comparable in size, split by a giant middle desert (literally and figuratively) And has two grids. Balancing the east coast grid is sometimes hard. Its weak, badly in need of capital investment and somewhat mired in inter-state/federal madness. Personally, I think privatizing the utility function was insane. There are some cool things which emerged after the 1970s grounded capital investment: High Voltag…

Among US utilities, local public utilities seem to work best. Federal run facilities are deeply mired in bureaucracy and acquisition guidelines, while fully private power companies are prone to get bought out by large investor conglomerates and end up too driven by quarterly profit to invest in maintenance.

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

#103

Post by lmm »

jdswain wrote: post #68
aidenn0 wrote: post #5

Earlier quoted context omitted.

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.

A large grid is harder to manage and runs the risk of a cascading failure. Especially as HVDC is a lot cheaper and more efficient than it used to be, there's an argument we should actually be breaking our grids down further.

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

#104

Post by deaddodo »

kazinator wrote: post #43
labcomputer wrote: post #34

Earlier quoted context omitted.

> 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…

The advantage of three phase over two is that three phase can energize the coils of a three-phase motor so as to create a rotating magnetic field. No extra circuitry is needed. Two-phase cannot do that when the phases are 180 degrees apart; opposite polarity is as good as a single phase. It would work if the two phases were 90 degrees apart. A two-phase motor operating on single phase (or 180 degree two phase) needs…

This video actually explains the reasoning for tri-phase power and it's advantages in a succinct manner, for anyone still confused:

https://www.youtube.com/watch?v=4oRT7PoXSS0

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

#107

Post by himinlomax »

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…

> then there will be serious problems in connecting them together

No there won't. The article mentions DC power converters. They are not cheap, but since HV DC lines are better for long distance power transmission than three phase AC, it's killing two birds with one stone.

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

#108

Post by himinlomax »

crmrc114 wrote: post #14
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 numbe…

> Three phase systems actually are a carry over from the days of early induction motors

Three phase is better than one for transmission: you can pass more power for a given distance with a given budget of copper/aluminium wire. In other words, you have three wires rather than 2, but they can be lighter overall, and require less materials and fewer and less expensive poles.

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

#109

Post by [deleted] »

nickff wrote: post #27
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…

Three-phase systems are far more than a carry-over from early electric motors. Cars, which have no legacy compatibility issues also use three phases. Three-phase power is a very good balance of simplicity of transformation and rectification with even-ness of loading. You have to remember that alternators and generators are loading mechanical systems, so it's a bad idea to have huge cyclic variations in the load, whic…

[deleted]

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

#110

Post by lucioperca »

kelnos wrote: post #100
kalleboo wrote: post #81

Earlier quoted context omitted.

> I continue to be amazed how many devices still ship with only two prong plugs (everywhere: Europe, North America, Australia...) even if those prongs are polarized Because most devices these days have plastic cases (Class II double insulated), so there's nothing metal to touch to get shocked even in the case of a fault. That coupled with how GFCI/RCDs are being widely adopted as well leads to grounding not being as…

I'm (mostly) with you on the plastic casing, but in general (in the US at least) you only see GFCI in kitchens and bathrooms. Meanwhile I'm sitting 2 feet away from a nearly completely metal lamp with a two-prong plug.

Find this very scary not having RCD on some plugs even with 120 Volts. Sure 240v with RCD will give you a massive shock but still will very unlikely kill you. No RCD on the other hand can be fatal on 120V: https://edition.cnn.com/2017/07/18/health/teen-bathtub-elect...
Post reply on HN