A Nationwide Survey of Recorded Information Used for Calculating Distribution Reliability Indices

Reliability is one of the most discussed topics in the power industry today. Although many questions are being asked about the reliability of utility systems across the nation, there are currently no standards for recording or measuring interruption minutes, number of customers affected, major events, whether to include transmission and or distribution as well as many other issues. The methods used for calculating the indices and the definitions for the information have a major role in calculating reliability measures as defined in a recent IEEE standard. This paper will provide the results of a nationwide survey on the recording or measuring of the data used to calculate reliability indices and associated practices. It will point out some of the pitfalls of using differing methodologies in the recording of data behind the measures. These differences often cause discrepancies when comparing reliability indices between utilities.