The other day, I mentioned that with thyristors connected to buck and boost converters, we could have built a much more efficient Direct Current electricity grid without the inherent losses from impedance with Alternating Current. We use 60 Hz AC mainly because it works well with (large) mains transformers and has a relatively low impedance, but it still has a lot of losses from impedance compared to direct current — and causes radio noise and hum. A high-voltage, direct current grid would not only be more efficient, you could bury direct-current lines easier, and not have to worry about storm damage.

The one issue I didn’t really address is the inherent dangers of high-voltage direct current — namely the difficulty of quenching arching, due to the lack of zero voltage crossing point. Direct current, especially high voltage direct current is difficult to break, as if you break mechanically, it will arc over — quite a long distance as the natural quenching of the zero voltage crossing point doesn’t exist like with AC. You can safely break a DC current using a thyristor, but what happens if a power line mechanically fails? It could arc over for some time, before fully breaking, causing enormous amounts of heat to be produced in the mean-time, turning large sections of wire into plasma.  A high-voltage alternating current line might arc over and burn for a while, but it would relatively quickly break the connection, once enough of the line vaporized and sufficient air gap existed and the zero-point was crossed.