Undervoltage load shedding improving security as reasonable measure for extreme contingencies

This paper highlights the effectiveness of undervoltage load shedding as reasonable measures to avoid cascading such as August 14^th outage against extreme contingencies. The security of decentralized UVLS program can be improved without degrading dependability by adding continuous voltage decay detection technique, on which TEPCO has long history. Observations on August 14^th outage and existing UVLS applications are also covered as related topics.