All of the recent discussions about the proposed mega grid got me thinking about what it takes to make it happen. It is made up of many building blocks that are available today. They include power electronics in the form of dc converter stations and FACTS devices. It also consists of components such as dc hybrid breakers, marine cables, and HVDC transmission systems. These devices have been around for many years, but today we are thinking about utilizing them in an integrated system. The idea is to form a super grid composed of ac and dc components that are being combined to move power safely and efficiently.
One of the key points in this endeavor is the development of Ultra High Voltage DC (UHV DC). UHL DC has been around since about 2009. The voltage rating is ±800. The first ±1100 kV UHV DC was announced by ABB for a project in China. Transmission lines of these voltages can carry tremendous amounts of power over extremely long distances with less losses than an ac line at lower costs. Here is a video that gives a good overview of this technology and how it is being used.