Oh and used voltages/tension on most grids worldwide go up to more than half a million volts with some systems using even more than a million volts with +-500 to 800KV/DC between lines. Here in the Netherlands we use 110/220/380KV for the main transport grid and a whole lot of underground/see DC links that connect GB/Norway/Germany and more country's to the Netherlands.
This lecture is a bit outdated. Texas is connecting to other grids,not much yet but they are doing it. High voltage DC is used more and more as the cheap way to transmit large amounts of power worldwide. Also DC gives network operators more time in case of shorts lightning-strike or other failing systems that trip breakers some seconds. DC has the advantage that it can be stored in buffer capacitors,if there is one second of brownout those caps can supply the DC/AC converter its power.
