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 to ground - No reflections due to Z mismatch - You can lay a cable underwater (basically impossible with AC) - you can connect incompatible grids

HVDC is still fairly expensive (obviously compared to a lump of laminated steel) so it’s used for very long lines, or other special needs.

But it’s revolutionized the field.

AC still has many advantages and won’t go anywhere, especially last-mile to medium range:

- arguably safer since an arc fault can self extinguish - switches are much cheaper to build - cheap electric motors - cheap ability to scale V