Quantitative evaluation of permanent outages in distribution systems

This paper is primarily concerned with the formulation of a group of simple equations which can be used to provide numerical estimates of the rates and durations of system load point failures. The reliability indices obtained by an existing approximate technique²and by the equations developed in this paper are compared with those obtained by a Markov approach using a two state weather model. An equivalent component formation method suggested in the literature⁵is investigated. The paper shows that this method gives results which are no better than those obtained by the approximate technique². The modified equations presented in this paper provide reliability indices which compare very closely with those calculated by the Markov approach. The concepts developed are extended to more complex configurations in which loadpoint reliability parameters are obtained by the technique of failure modes and effects analysis and therefore eliminate the necessity of forming equivalent components.