To identify a set of terms and definitions which can be used to calculate power distribution reliability indices and factors. To present a set of terms and definitions which can be used to foster uniformity in the development of distribution service reliability indices and factors. New IEEE Standard - Superseded. Superseded by IEEE Std 1366-2003. Useful distribution reliability indices, and factors that affect their calculation, are identified. This guide includes indices that are useful today as well as ones that may be useful in the future. The indices are intended to apply to distribution systems, substations, circuits, and defined regions.