Switch-system troubles at the Tokyo Electric Power Co.’’s substation in Tokyo’’s Koto-ku blacked out an extensive area covering the capital and six prefectures at about 4 p.m. on May 22nd. At Tokyo Disneyland, the Big Thunder Mountain roller coaster and several other rides stopped for up to 40 minutes. A Disney official said, “This is the first case of rides halting because of a power failure in a few years.