Lower frequency (50/60 Hz) AC is the only really useful choice for transmission on low cost long runs (think 100 km and more). To push high voltage DC on long runs generally means special cables and possibly super conductors. Pushing 60 Hz AC at 230 kV goes over simple cables (granted with fancy insulators for holding it to the towers).
Stepping AC up or down in voltage is simple, build a transformer. Stepping DC up or down requires switching electronics, which usually will also have a transformer (if the step is reasonably large).
That distribution of power inside houses is AC still is a legacy problem and because half the things in your house still use AC power motors, and generally those things are the big current consumers (air conditioning, fridge, clothes washer, etc). Your PC, phone, etc which run on DC draw tiny amounts of power in the typical house compared to an air conditioning unit, but running an air conditioning unit on DC would likely require an inverter to generate the AC power for the compressors and fans.
Motors like AC, it's what makes them spin best. "Brushless DC" motors use an inverter system, usually. Even brushed DC motors effectively generate AC inside themselves with commutation.
> Lower frequency (50/60 Hz) AC is the only really useful choice for transmission on low cost long runs (think 100 km and more). To push high voltage DC on long runs generally means special cables and possibly super conductors. Pushing 60 Hz AC at 230 kV goes over simple cables.
Not correct. High-voltage DC runs just fine on regular copper. (In fact, in some cases you only need a single conductor because you can use the Earth as the return. This isn't typically in the design spec, but it's sometimes used as a backup plan.) Low-voltage DC requires superconductors, because pushing low-voltage anything any distance requires superconductors.
The only reason most transmission is over AC today is Tesla (the man, not the car) didn't have power electronics to step-up or step-down voltage. We now have the technology to change the grid to DC if we want.
> We now have the technology to change the grid to DC if we want.
True, but the cost of each endpoint is significantly higher for DC than AC, especially at high power. I would imagine the reliability and longevity of power-equivalent DC converters would also be lower than that of AC units. That is to say, a complicated electronic component with many critical parts is more likely to fail than a simple transformer.
Copper is quite expensive for long cable runs, but your point about pushing lower voltage DC needing super conductors is true compared to high voltage DC not needing super conductors.
You can also use the earth as a return in an AC system. This is often done with more remote areas when distributing power in order to keep the cost down. It has downsides, but it works well enough.
> Lower frequency (50/60 Hz) AC is the only really useful choice for transmission on low cost long runs (think 100 km and more). To push high voltage DC on long runs generally means special cables and possibly super conductors. Pushing 60 Hz AC at 230 kV goes over simple cables.
I don't think that's true. The point about HVDC is that is is cheaper to do for longer runs than HVAC (that's why they are planning to use HVDC for the new long distance power lines in Germany).
Why would you need special cables for HVDC and not for HVAC? DC has less losses than AC for the same current.
The only reason AC is used for transmission lines right now is that technology for HVDC wasn't quite ready/cheap enough. It is now.
Stepping AC up or down in voltage is simple, build a transformer. Stepping DC up or down requires switching electronics, which usually will also have a transformer (if the step is reasonably large).
That distribution of power inside houses is AC still is a legacy problem and because half the things in your house still use AC power motors, and generally those things are the big current consumers (air conditioning, fridge, clothes washer, etc). Your PC, phone, etc which run on DC draw tiny amounts of power in the typical house compared to an air conditioning unit, but running an air conditioning unit on DC would likely require an inverter to generate the AC power for the compressors and fans.
Motors like AC, it's what makes them spin best. "Brushless DC" motors use an inverter system, usually. Even brushed DC motors effectively generate AC inside themselves with commutation.