Further development of the Overload Risk Index, an indicator of system vulnerability

This paper develops and expands on a previously devised vulnerability index in an attempt to make the index more robust in describing a power system´s total vulnerability level. The previous index was derived using a dc load flow analysis using line outage distribution factors and Monte Carlo simulation that incorporated the unavailability rates of the transmission lines within the system. The updated index incorporates the following improvements: (a) tests to determine bus islanding in the system, (b) steady-state stability tests, (c) an optimal power flow to determine a more accurate steady-state point of operation, (d) ac analysis for a greater degree of accuracy, and (e) generator failures in addition to line failures in order to improve the scope of the index. Additional case studies have been performed which analyze the effects of these new test variables on the index.