[xnyan]

I’m sure you’ve heard something like “alternating current is more efficient than direct current for transmitting power”, but this is only true in specific conditions. At very high A/C voltages, the magnetic field created by the alternating current “pushes” elections away from the core of their conductor. This has the same effect as using a smaller diameter conductor, increasing heat which increases resistance and reduces efficiency. At sufficiently high voltages and distances, DC can have less loss and also has the added bonus of not needing to consider differences in A/C frequency when transmitting power between areas that have dissimilar electrical grids.

[newZWhoDis]

DC is more efficient at basically any voltage. AC won because its voltage is easily stepped up and down, and high voltage is superior for long range transport vs low voltage.

But high voltage DC for huge, inter-state transport lines makes a lot of sense.

[dreamcompiler]

AC is never more efficient than DC. AC was easier to step up and down than DC 120 years ago. That's the only reason we use it*, despite worse efficiency.

* Motors are the other reason. Big electric motors in 1900 ran better on sinusoidal AC than DC. We have much better motor technology today, plus power semiconductors to control them. So motors are no longer a reason for the grid to be AC.

[Gibbon1]

Interrupting AC is also easier than DC because DC creates sustained arcs.

[sbaiddn]

"At very high A/C voltages, the magnetic field created by the alternating current “pushes” elections away from the core of their conductor. "

Thats a frequency effect and is addressed in power-lines. The line cores are of steel cable to provide strength, but is a poor conductor. The inner core supports the Al "shell" that actually carries the current.

[ethbr0]

Or as we learned in electromag physics, why stranded wire can carry more amperage than solid (because it has more surface area).

Note: Generalizing and making a lot of assumptions. This statement is not encouragement to ignore AWG markings or limits in any way, as the effect isn't that large.