Development of distribution system reliability and risk analysis models

The two reliability models, their testing, and the modifications of a unified distribution planning model to calculate reliability indices are described. The historical reliability assessment model HISRAM is designed to suit most utilities. Four implementation levels with different input data requirements and output capabilities permit a utility to select a level appropriate to its needs. User-defined divisions, causes and output options further add to the program flexibility. A unique feature of HISRAM is the program generation of the appropriate outage reporting form following level selection and initialization. This allows the engineer to review data input requirements before field implementation. It has the capability of estimating component failure rates and restoration times upon provision of suitable input data. The predictive reliability assessment model PRAM uses continuity criteria, together with component failure rates and restoration times to calculate load point indices. System indices similar to those produced by HISRAM are also calculated. Varying degrees of detail for representing the protection system are available through three user-selected models. Both models were tested through application. The conclusions and recommendations of the entire project are included.