Computing probability of instability for stability constrained electric power systems

Prevention of instability can be costly as it typically requires that system operation be constrained in a manner that increases the cost of providing electric energy. Developing a reasonable balance between economy and risk of insecurity requires accounting for the random nature of disturbances which can result in security violations. In this paper we present two methods for calculating the probability of instability due to transient instability. The methods are illustrated using a model of the Arizona portion of the WSCC system where, under weakened system conditions and no remedial actions, there are two separate contingencies which could result in a transient instability problem.