DC transmission lines are coming back.
It has some good advantages in certain situations that are being realized more and more.
One of the big advantages is there is no need for synchronization between different grids to transfer power back and forth.
Really long distances have less loss with DC, apparently.
http://en.wikipedia.org/wiki/High-voltage_direct_current
“Really long distances have less loss with DC, apparently.”
That is probably true, since even at 60HZ some power is radiated (but it is negligible), however the cost and efficiency loss of converting it back to AC is tremendous.