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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?

#71

Post by marcosdumay »

djsjbsjd wrote: post #67
marcosdumay wrote: post #62

Earlier quoted context omitted.

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.

A quick search will lead you somewhere like here: https://en.wikipedia.org/wiki/High-voltage_direct_current.

> Most HVDC links use voltages between 100 kV and 800 kV.

By contrast, high voltage AC lines are around 10kV to (very rarely) 100kV. AC presents some more problems to high voltage than just phase synchronization (so even two point lines are DC), but the gains come mostly from the HV part, and AC is avoided because it doesn't play well with HV, reverting the gains.

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

#72

Post by swatson741 »

djsjbsjd wrote: post #66
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 t…

It looks like most of those points are because you wouldn't necessarily be transmitting power over frequency like you would with AC. But, if we're transmitting over long distances wouldn't we end up transmitting the DC in frequency to avoid attenuation loss?

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

#73

Post by justatdotin »

ggm wrote: post #58
siddboots wrote: post #29

Earlier quoted context omitted.

> And has two grids. Not just two. There's also the Darwin/Katherine system which serves about 150k customers. The NWIS and Alice Springs system both have 20k+ customers. Australia has some really interesting power systems.

Sorry I didn't capture that. I bet the NT gets better service outcomes than either WA or east coast, sooner (because more focussed)

there's issues with decades of one provider also owning the infra. It got split up in recent years, but we've yet to see new providers connected.

in the top end, fruitbats and cyclonic storms are common disruptions

its got better in the suburbs since lotsa wires went underground, but just a few km down the highway and the grade of service drops.

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

#74

Post by fireattack »

fomine3 wrote: post #65
fireattack wrote: post #64

Earlier quoted context omitted.

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…

Thanks for the links! I do found that inverter AC seem more popular in East Asian countries. But then again, they don't use central air conditioning in residential as much as the US do, so probably not an apple to apple comparison.

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

#75

Post by [deleted] »

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…

[deleted]

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

#77

Post by 7thaccount »

msisk6 wrote: post #13
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?

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...

Most of them are ageing too.

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

#78

Post by brnt »

marcosdumay wrote: post #71
djsjbsjd wrote: post #67

Earlier quoted context omitted.

“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.

A quick search will lead you somewhere like here: https://en.wikipedia.org/wiki/High-voltage_direct_current . > Most HVDC links use voltages between 100 kV and 800 kV. By contrast, high voltage AC lines are around 10kV to (very rarely) 100kV. AC presents some more problems to high voltage than just phase synchronization (so even two point lines are DC), but the gains come mostly from the HV part, and AC is avoided be…

Standard (long distance) lines in Europe carry 380kv AC.

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

#79

Post by edogg »

marcosdumay wrote: post #71
djsjbsjd wrote: post #67

Earlier quoted context omitted.

“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.

A quick search will lead you somewhere like here: https://en.wikipedia.org/wiki/High-voltage_direct_current . > Most HVDC links use voltages between 100 kV and 800 kV. By contrast, high voltage AC lines are around 10kV to (very rarely) 100kV. AC presents some more problems to high voltage than just phase synchronization (so even two point lines are DC), but the gains come mostly from the HV part, and AC is avoided be…

Ac transmission lines are regularly 500kv with some famous ones in Quebec being 750kv. I believe there are even higher now.

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

#80

Post by FrumpyDonut »

imoverclocked wrote: post #49

The main point of this article has nothing to do with the technical details of power transportation and everything to do with politics and corruption of our academic/research institutions. It’s amazing how an anti-fact leader can have such corrupting influence on institutions that are building tomorrow’s leaders.

You'd be hard pressed to find too many facts in a study like this. These are largely conjecture with a list of assumptions and simplifications longer than the study itself. NREL is particularly famous for these. The reality is there are as many people who think the grid should be split into more pieces as there are people who think it should be unified.

But it's a fair point regarding the political influence in these type things, though it's not just the current administration. In a couple of months we will all be changing the verbiage of our proposals from resiliency, security back to renewable integration to satisfy our funding overlords.

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