The power system failure on July 23, 1987 in Tokyo

A power system failure occurred at 1:19 p.m. on July 23, 1987, in the service area of the Tokyo Electric Power Company Inc. The unusually hot weather led to concentrated mass consumption of electricity, causing a failure which affected 2.8 million customers in the area. There were three major causes of this failure: the power demand level on that day was unusually high; the rate of demand increase exceeded previous levels; and air conditioners which have characteristics such that a fall in voltage leads to a rise in current are in widespread use in Japan. The failure is analysed and countermeasures to mitigate future power failures are presented.<>