In my July 19 column in The Japan Times, I write about how the heck Japan ended up with two separate electrical grids, a topic very much in the news because the incompatibility of the grids greatly exacerbated the power shortage that resulted from the March 11 earthquake and tsunami. (And while we’re on that topic, please check out my updated list of power-saving tips specific to Japan.)
The diagram above shows the dividing line between the grids. All the electricity to the west (left) of the line operates at 60 Hz, while everything to the east (right) runs at 50 Hz. But the truth isn’t quite that neat. What that diagram doesn’t show is that Nagano Prefecture is a kongō chiku 混合地区, or all mixed up. Most of the electricity in the prefecture oscillates at 60 Hz, but the municipalities shown in green on the diagram below, borrowed from Chubu Electric’s website, get their juice at 50 Hz. Now wouldn’t you like to know how the heck that came about?
Alice Gordenker アリス・ゴーデンカー 
The obvious question I haven’t seen answered anywhere is why the conversion wasn’t done after WWII. With most of the urban areas in ruin and still so little of the countryside electrified, the conversion should have been the proverbial no brainer during the rebuilding.
I wonder if anyone has calculated how much money has been wasted post-WWII because of this as major appliances and anything else that draws a substantially amount of electricity can’t be moved from/to or used in the different electrical grids, meaning that everything falling into certain power categories needs to be made in two versions.
The explanation I got from the source quoted in my article was that the unification wasn’t done in 1939 because it was difficult to get the necessary supplies and equipment because everything related to machinery was going to the war effort. Then after the war, when unification was discussed again, the feeling was that it was more important to get a stable supply of electricity restored, and then expanded, and that this was not the time for niceties like unifying the country on one frequency. Apparently the GHQ never issued any orders on this during the Occupation, which is also surprising.
I just read your Japan Times article on the historical background and present situation of the two power grids in Japan. It’s good reading, but I would like to add one point.
Your comment that “. . . The standard frequencies for AC are 50 and 60 Hz, and there’s no technical reason to use one frequency over another” may be correct from the engineering standpoint, but from the human standpoint I think that there is a reason to prefer 60 Hz: in plants or even large office spaces that operate fluorescent lights at 50 Hz, visible flicker is apparent to the casual observer, and cannot be good for the work efficiency of people who sit under such lighting. In similar spaces using fluorescent lights on a 60-Hz grid no such flicker is apparent (except, of course, when the bulbs are defective or at death’s door). In my particular case, any fluorescent lighting gives me headaches, but the reaction is much worse under 50 Hz.
Best regards,
Larry Cannon
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