Hokkaido blackout could happen in other regional areas: experts

The large-scale blackout that affected Japan's northernmost prefecture of Hokkaido after the Sept. 6 earthquake could happen in other areas, experts related to Japan's electric power grid warn.

Due to the earthquake, which measured a maximum 7 on the Japanese 7-point seismic intensity scale in some areas, all of Hokkaido Electric Power Co.'s (Hokuden) thermoelectric power plants were put on emergency hold, plunging all 2.95 million households on the island into darkness.

However, the possibility cannot be overlooked of the entire grid carried by one of Japan's other major power suppliers also going down in a large temblor. While the blackout this time was caused by multiple factors, as long as preventative measures are not seriously considered, the same trouble could occur on other power grids, particularly those handling relatively small power demand, experts say.

According to the Federation of Electric Power Companies, the case with Hokuden is the first large blackout to hit the entire power grid of a major power company since Japan's network was divided into the current 10-company system after the war. In the aftermath of the Great East Japan Earthquake in March 2011, power was lost to a total of 8.7 million households on Tohoku Electric Power Co. and Tokyo Electric Power Co. (TEPCO) grids in northeastern and eastern Japan, but it did not lead to a complete outage in one region controlled by a single provider.

According to Hokuden, the power demand for the prefecture was at 3.1 million kilowatts when the earthquake struck. Of the power stations on the island, the Tomato-Atsuma thermal power station, which has an output of 1.65 million kilowatts, was handling the most demand. When it automatically shut down due to the temblor, the balance of output and demand was disrupted, and all the other thermal power stations on the grid went down as well.

The reason for this disruption is thought to be that even during peak demand on Sept. 5, Hokkaido residents and businesses were only using 3.8 million kilowatts of electricity. Even if one of the power stations on TEPCO's grid, which also handles a maximum of 1.65 million kilowatts of demand, were to automatically shut down in an emergency, it would not affect the relatively larger grid -- which handles a peak demand over 50 million kilowatts -- and it would not lead to a large-scale power outage.

On the other hand, for Hokuriku Electric Power Co. in central Japan and Shikoku Electric Power Co. in southern Japan, and other regional companies that handle a peak demand in the range of 4 million or 5 million kilowatts, losing a power station like Hokuden that was providing 1.65 million kilowatts could cause a similar burden on the grid and runs a high risk of leading to a large-scale blackout.

(Japanese original by Masahiro Kawaguchi, Business News Department)