Analysis of Contingencies Leading to Islanding and Cascading Outages

We develop and test an efficient simulator to estimate the sequence of automatic events that follow a contingency leading to islanding and cascading outages. The simulator is based on a quasi-steady-state model o that includes island identification, island power balance, primary frequency regula tion, under-frequency load shedding, over-frequency generator tripping, and island load flow. The simulator first identifies the islands into which the network splits through the null space of the network susceptance matrix. Each island is then analyzed for a surplus or deficit of primary frequency regulation, followed by any necessary corrective load shedding or generation tripping. Next, each island's load flow is solved and tested for possible new line overloads and corresponding line tripping. The overall contingency analysis reruns until either all loads are shed or the islands can operate at some reduced load level within their operational bounds. Simulation results are presented for a 10- bus, 13-line system and for the IEEE 73-bus, 119 line reliability test network.