Isolation and restoration policies against power system collapse

This report discusses characteristics of severe system disturbances and describes measures applied by utilities against wide-spread blackouts, including currently applied special protection schemes against power system collapse. Normal protective relays used for fault clearance are not considered. Emphasis is placed on: circumstances which could lead to severe disturbances; utilities policies for preventing system collapse; SPS in operation; performance of SPS against disturbances; interaction of SPS and the power system.