Design and operating experience with fast acting load shedding scheme in the Entergy system to prevent voltage collapse

This work describes the design and development of load shedding scheme for South Mississippi region and discusses the operating experience with load shed scheme in the Western region. This scheme is fully automated and utilizes the SCADA system to perform load shedding without any manual intervention. The load, bus voltages and over excitation relay controls of the generating units have been considered in the decision logic. Similar UVLS scheme was implemented in the Western region of the Entergy system. The main difference between two schemes is that one monitors transformer loading and status while the other monitors over excitation relay operation at the generating unit. This type of scheme is designed to handle any abnormal condition that might cause voltage collapse.