From NPR Blackouts That Could Continue For Years

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The problem is these rolling blackouts could continue for many months — even years.
“This is a real problem for those factories which need uninterrupted supplies,” says professor Tatsuo Hatta, president of the National Graduate Institute for Policy Studies in Tokyo. He says the situation might cause some companies to move.
“It’s clear that from their viewpoint they’d better move their plant to the western part of Japan where electricity is plenty.”
It might seem much easier to send the surplus power from one side of Japan to the other to ease the blackouts. But that’s harder than you might think, Hatta says.
“One major problem is that the east and west of Japan have different electric cycles and the capacity of the connectors are very much limited,” he says.
That’s partly an accident of history. Eastern Japan followed the German model and has a 50-cycle electrical power grid. The western part of Japan used the American model and has a 60-cycle grid. Transferring power from one grid to another requires a very expensive facility. And there are only three connections between eastern and western Japan. [ed. note wikipedia says 4] That bottleneck means the power transfer is just a trickle, even during this national emergency. Creating more capacity would take years. …

Somewhere along the way, you would have thought, they would have standardized on one frequency or another (e.g. after World War II), but standards have strong lock-in, even in a defeated country. Apparently in the US, Southern California Edison did not convert to 60 Hz (from 50 Hz) until 1948.
Choosing a single standard increases economies of scale, has network effects, and improves redundancy (unless the standard itself fails for some reason).