Intentional islanding and adaptive load shedding to avoid cascading outages

System disturbances that involve several interconnected areas across the grid are uncommon, but they occur more frequently than predicted. Some are weather-related events; while some are system initiated cascading events that can be prevented. The power grid is capable of surviving one or two contingency events, but with multiple contingencies the system may collapse if the disturbance is severe. The transmission systems of today are more liable to cascading outages than they have ever been in the past. Effective countermeasures are therefore a necessity. Determination of the line outages that lead to disastrous consequences, forced islanding schemes and load shedding techniques have been explored individually. A plan integrating all the three defense mechanisms is studied. Load shedding is sometimes executed to reduce the imbalance and re-establish the normal operating conditions in time to avoid system collapse. Under emergency conditions it is desirable to split the system in a specific manner, into smaller areas accordingly so that they are capable of sustaining nominal system operation. The areas are mostly pre-planned, specified by offline studies. Controlling the switching equipment, circuit breakers and relays enable forced islanding. Distributed generation can play a vital role in maintaining the generation-load balance. Results obtained from the application of this technique indicate that it can be a powerful approach for secure operation of power systems --Abstract, page iii