The effect of reducing momentary outages on distribution reliability indices

One method of reducing momentary outages is to eliminate the instantaneous trip on the feeder breaker, thereby making all lateral faults permanent. It is pointed out that while this practice does indeed reduce the number of momentary outages, it can adversely impact reliability indices that may be reported to regulatory commissions. The author studies the effect of converting momentary outages to permanent outages on distribution feeders, and examines the relationship of momentary outages to good power quality. The effect on reliability of adding reclosers to distribution feeders is also discussed. It is concluded that reducing the number of momentary outages by methods (lightning arresters, tree trimming) other than the removal of feeder selective relaying may be more advantageous