25/04 FROM SQUARE ONE / Mismatch leaves nation divided

The Yomiuri Shimbun

The country's electricity grid is effectively split in two by mismatched power frequencies--the supply is 50 Hz in eastern Japan, and 60 Hz in western Japan. The "electricity border" runs from Itoigawa in Niigata Prefecture to the Fujigawa river in Shizuoka Prefecture.

This incompatibility severely limits the transfer of electricity from western Japan to the Tokyo metropolitan area, where it is currently in short supply.

It is rare for a single country to operate on two different power frequencies.

Most modern electrical appliances are compatible with both frequencies, but until the mid-1990s, products were often compatible with only one.

The split originated in the Meiji era (1868-1912), when two power companies introducing generators to Japan decided on different models. Tokyo Dento Co., a predecessor of Tokyo Electric Power Co., chose a German-made 50 Hz generator, while Osaka Dento Co., a predecessor of Kansai Electric Power Co., introduced a U.S.-made 60 Hz generator.

Switching to a common frequency was debated after World War II, but efforts were instead concentrated on the more urgent task of increasing power supply to facilitate postwar reconstruction. Frequency-conversion facilities were later built that enable electricity to be shared between east and west.

In 1965, Electric Power Development Co., commonly known as J-Power, built a frequency-conversion station in Shizuoka Prefecture. TEPCO installed a station in Nagano Prefecture in 1977, and Chubu Electric Power Co. established a station in Shizuoka in 2006.

However, the three stations combined can only convert 1 million kilowatts of electricity at a time--too little to make up for TEPCO's power shortfall, which was nearly 10 million kilowatts immediately after the March 11 earthquake.

Calls to unify the nation's power network under a single frequency remain strong. But doing so would require a major infrastructure overhaul--including facility upgrades and land purchases--that would cost up to tens of trillions of yen, according to experts. Realizing unification of the nation's electricity grid could depend on the government taking the lead, as it did on the digitization of terrestrial TV broadcasting.

(Apr. 25, 2011)