Probabilistic angle stability index

This paper develops a novel concept and computational framework of a probabilistic transient stability index called the expected angle stability margin, EASM, for electrical power systems. This new integrated index provides a common transient (angle) stability characteristic over a set of possible system configurations and contingencies, disturbances and faults, and load demand levels on a probabilistic basis. The EASM expresses a general transient stability "fitness" of the system for a variety of operating conditions. The set of contingencies covered by the index is selected on the basis of a new developed index called the weighted probability index, WPI. The WPI index accounts for the contingency probability, economical, social and system values of the corresponding system configurations. The proposed EASM can be effectively used to assess the average transient stability of the power system. It also evaluates the impact of decision-making in power system reinforcement and expansion planning, and provides an objective for formal optimization procedure in combined stability/reliability studies. A computational scheme for EASM is developed and tested using the IEEE 25-Bus Reliability Test System.