Fun fact: Japan uses BOTH 60Hz and 50Hz for mains electricity due to historical generator purchases. This means the Japanese electric grid is split into two regions that cannot easily share electricity.
The US alone has 3 grids (East, West and Texas). With the same frequency but still not connected.
In Switzerland trains use 16.7Hz but they are connected with large frequency inverters. Before it was with large motors / generators. Now its just static with electronic.
Exactly, DC is used for those links that would otherwise be out of synchronization. In Canada one of the DC links goes from the North American grid on the British Columbia Lower Mainland in Delta via a single underwater cable over to Vancouver Island. The water is the other conductor, and also keeps the cable cool.
I want to say this was part of the issue after the Tohoku Earthquake, my recollection was that some generators got brought in to support the ones that were flooded but were incompatible. However, I can not find any note of it in the timelines and after-action reports that showed up when I searched.
So possibly misremembering or fog of war reporting, or perhaps not important enough for the summaries.
I like the hypothesis by fomine3 on HN that "Japan's divided frequency situation made Japanese electric manufacturers to invent inverter for electrics (example: air conditioners, microwave, refrigerators). Inverter primary makes electrics controllable efficiently, also they can ship same product (same performance) for both 50/60Hz area in Japan."
