Causal Analysis of Distribution System Reliability Performance

Various misinterpretations of a utility's reliability performance by non-utility personnel can significantly compromise the reliable design and operation of industrial and commercial power systems. The methodology used to assess the historical reliability performance of utility electric distribution systems is outlined. Included is an overview of the process used to collect and organize the required interruption data as well as a description of the performance indices calculated for use in the assessment of the reliability performance assessment at different levels of the system. A three year reliability assessment of a utility's electric distribution system is presented to illustrate the application of the calculated performance statistics in planning, operating and maintaining distribution systems. The identity of the utility is not revealed for confidentiality reasons. The paper discusses the utility performance indices from two perspectives; the utility and its industrial and/or commercial customer