Reliability analysis of utility single feeder circuit supplies

The frequency and duration of interruptions at industrial and commercial facilities is dependent upon the reliability of utility power supplies to these facilities. IEEE Std. 493 -2007 presented the 1975 survey results of the reliability of electric utility power supplies to industrial plants which raises the question of how valid is this data today. This paper will present the results of a five year (2002 -2006) reliability study of 285 individual distribution feeder circuits to reveal the significant variance in the frequency and duration of feeder circuit unscheduled outages from different statistical perspectives. The paper will discuss and reveal the changing, temporal and spatial characteristics of the frequency and duration of feeder circuit outages and the difficulties in assigning particular reliability values for the utility supplying for a given facility.