A state transition model is developed for the distribution system in terms of the location and dynamic characteristics of operable components such as breakers

subsection switches and tie switches. Owing to the small quantity of the operable components

the number of states in this model is relatively small. Based on this model

all static components

including transformers

common power lines and cable lines

are partitioned into different kinds after the firstorder classification and then the secondary classification. System state transition under the failure condition is simulated only once for any kind of components

while the corresponding states’ failure frequency and failure duration are calculated. Then every load point’s reliability indices are obtained via simple multiplication and repeated addition calculations. Compared with the reliabilitynetworkequivalent approach

the model and algorithm presented for distribution system reliability evaluation with the contribution of the failure of relay protection system taken into account have higher speed and less calculating redundancy. Their effectiveness is verified with the results of IEEE RBTS.