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Comment by MentallyRetired | Hacker News Reader

Doesn't electricity have a limit on how far it can be pushed through a wire? Looking for a little enlightenment on this topic.

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Not really, that limit is only due to the wire resistance, which goes down with wire thickness.

There will be a delay of course, which is the cable impedance (inductance), mostly due to the speed of electricity not being infinite in a conductor.

A bit like there is no limit for the length of a stick you can push with your arm. There's only resistance if it's on the ground (push it in space to visualize a superconductor). It also has inertia (mass, which is inductance). And at longer lengths, you won't see the end move before the movement you impulsed has reached the end at ~the speed of sound in that material.

Now, to go a bit into the details:

A/C can also exploit "skin effect" where a high frequency A/C signal only travels on the outside of conductors. That way, you can make thinner conductors (just coat regular cables in an expensive conductor)... Up to a certain point, since if you need to carry more power, you need extra large cables, hollow ones, and/or multiple cables). That wastes part of the conductor: https://en.wikipedia.org/wiki/Skin_effect

With A/C, you can also use transformers, but not with D/C, which has traditionally been an hindrance to high-voltage DC. You have to generate alternative current, or use boost circuits (basically charge a capacitor at constant current to increase voltage). Cutting power in high-power A/C is simpler, since you can do it when voltage crosses 0 V.

I'm not sure what the pros and cons of both are when it comes to economics. It seems D/C is getting more affordable thanks to semiconductors: https://en.wikipedia.org/wiki/High-voltage_direct_current#Ad...

On the west coast of the US, we have a 3GW DC link between Portland (actually, The Dalles, a few miles from google's first datacenter) and Los Angeles. DC power transmission over long distances has less loss, and only requires 2 wires. Its 850 miles (about 1350km) https://en.wikipedia.org/wiki/Pacific_DC_Intertie

We ship all this renewable power to LA, and yet more than half my local (Portland) power makeup is coal.

Oh come one, that's small box thinking, you gotta look at the big picture. LA has a larger electricity demand than portland and it oscillates in a different pattern than portland. In the summer, due to AC, LA needs more peak capacity. However in the winter, the equation flips and now Portland needs that capacity to heat homes. Keeping all that hydro in washington to support the comparitively teensy population of 650k in portland is a waste, especially when demand is needed down south and not in the north and vice versa; this line serves 3 million in LA and represents half the LADWP peak capacity. I'd argue cutting LA off would force more coal plants to open than what is needed to electrify portland today.

Fantastic and valid points, though I think pkulak also has a fair point in identifying that this big picture setup negatively impacts folks in Portland via air pollution and other side effects of more coal plants than would otherwise be required.

On the other hand, that energy has to come from some place and this set up negatively impacts someone no matter where the coal plant is located. Maybe the coal comes from the cascades and it makes more sense to put the plant close to the source, rather than somewhere near LA and have to freight in the coal from the mines and deal with those externalities that might be worse than simply running a wire to LA.

You misunderstood me a bit, though I was pretty vague. I was just remarking on how we have enough local, renewable power locally, and yet burn coal. We could easily get our power from hydro AND send the majority to LA, but instead we don't. Probably because LA is willing to pay so much more for it.

I don't know the political climate in Oregon about hydro, but it's starting to turn a bit in Washington. Dams are pretty awful for salmon and so much of our ecology is salmon-based as well as the culture/livelihoods of Native Americans.

The biggest story in recent years was the Elwha dam removal. It's stunning to see how much the landscape has changed since: https://therevelator.org/elwha-dam-removal/

And a recent story about a Skagit river dam: https://www.king5.com/article/news/investigations/seattles-s...

I don't think anyone's seriously proposing getting rid of any of the major electricity producing dams though, just the minor old ones that are doing nothing of significance.

In raw economics terms, the price LA pays is lower than the cost of them opening their own coal plants, otherwise they would do just that. Therefore, it is for some reason cheaper to open a coal plant near portland (maybe closer to the coal source) and run a wire down to LA, than it is to come up with some other source of peak demand electricity for those 3 million people in LA who rely on this capacity. A private market does what is profitable, ultimately.

Maybe if we had public utilities, however, we would actually invest in 'unprofitable' nuclear energy and save our planet in the process, since we wouldn't be beholden to making shareholders a profit.

Power loss is a function of current. So major transmission lines use very high voltage to lower the current (and thus the power loss). Of course, there are losses at the transformer(s) the step the voltage up and down. Unsurprisingly, it's a very use-case-dependent engineering problem.

Not really. The higher the volts, the fewer amps and losses. So, if you can just get the voltage high enough, there's really no limit.

Not sure what the current highest volt transmissions are. Maybe a couple million volts on some DC lines? But I think that's good enough for hundreds, if not thousands, of miles of efficient transmission.

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