This paper illustrates the application of a conditional probability approach to the determination of a reliability index at any point in a composite system. A general design criterion is postulated in terms of quality of service rather than continuity. Using a Markov approach, it is shown that the effect of storm associated failures on the system failure probabilities is dependent upon the degree of redundancy in the configuration under study. The effects of shunt compensation, on-load tap changing, and variations in allowable voltage levels on the reliability of a simple configuration are illustrated. Using the techniques described in this paper, it is possible to arrive at a measure of steady-state adequacy for any point in a system and, particularly, at those points at which major transmission terminates and subtransmission begins. Copyright © 1969 by The Institute of Electrical and Electronics Engineers, Inc.
