Yunhwan Lee, Taegyun Kim, Jihun Kim, Byongjun Lee, Bu-il Kang, and Jongman Cho, “Multi-level
UnderVoltage Load Shedding Scheme Considering Rate of Change of Voltage for Voltage
Stability,” The transactions of The Korean Institute of Electrical Engineers, vol.
58, no. 12, pp. 2335~2341, 2009.