Wonder how much complexity using AC adds to this? With DC you would not have to worry about frequency and phase matching. But then you need to convert the DC back to AC at some point.
That is not possible with DC.
High voltage DC is hard as it requires solid state components which are expensive to make, and prone to blowing up (aka relatively fragile). AC to DC and vice versa also adds non-trivial losses.
High voltage DC (to a first approximation) doesn’t suffer from inductive losses however, which makes it much more efficient when near conductive stuff like the ground or seawater.
It’s also ‘simpler’ (doesn’t have things like phase or frequency) which is convenient if doing things like transferring power between two power grids with dissimilar frequencies or phase.
They each have their place.
Funny enough, AC+DC (hybrid transmission) on the same lines is active research.
https://electrical-engineering-portal.com/download-center/bo...
One thing to remember is that it is common for the conductor to have a strengthening core: this allows operation at a higher temperature (which means a higher current), and it allows for a longer distance between support towers (which means lower construction costs). If you're going to put some poorly-conducting steel or carbon fiber in the center of the conductor anyways, why worry about the skin effect?
Besides, those conductors are massive already. At the highest voltage levels, a single set of conductors is carrying multiple gigawatts of power. Even if it were technically viable, would you want to build a single 16GW connection? If it fails, you're going to have serious trouble compensating for that - it's probably wiser to build it as 4x 4GW connections.
HVDC also has its own issues with converter losses and not being able to easily step down to lower voltages. It's very nice for distances in the hundreds of kilometers, but it's just not a viable alternative for short city-to-city links.
AC is amazing for that due to the ease of making/using transformers, as well as efficiency in situations with simple spinning motors, and due to the way it behaves is ‘more safe’ in a number of fault condition.
AC is much easier to manage with fault protect as it has a zero volt crossing point each cycle, and safer for humans from a shock/electrocution hazard perspective due to the reversing voltage/zero crossing point. Muscles won’t ’freeze’ in a given position like with DC, but rather spasm (though it can be so fast it’s basically the same thing), and the zero voltage crossing point tends to allow arc self extinguishing at much lower thresholds.
But the same thing that makes it much easier to voltage regulate (using transformers) is also what creates inductive losses and complicated in some other scenarios (like conversion to DC for non-motor loads, PF issues, etc.).
No one needs a bridge rectifier for a DC to DC power supply, for instance, and DC to DC ripple is dramatically easier to deal with than typical half phase residential AC.
Commercial can have the luxury of 3 phase AC at least, but that is also typically at power levels that it still isn’t going to be cheap building a AC to DC power supply. And god help that power supply if you get phase imbalance.
I'm short, it's this way for a reason. The complexity is nessessary.
On an AC transmission line, I suppose any corona discharge going on shuts off and restarts every time the voltage reverses. They make a characteristic buzz in humid conditions.
For non-physicists: https://electronics.stackexchange.com/questions/128986/why-u...
Summarizing a couple of year of very annoying electrical studies: Yes
You can't believe how much
The issue is one of technology (having high powered switching components only took of in the last 30? yrs or something) and legacy
(Edit: IGBTs are from the 80's though it seems the 1st generation wasn't that great, IGCTs from the late 90s https://mb-drive-services.com/experience-with-igct-based-vfd...