U.S. distribution grid reliability continues to decline. Between 2013 and 2020, SAIDI increased from 106 to 119 minutes when significant weather events were excluded. With major weather events included, it rose from 180 to 342 minutes. Aging infrastructure and extreme weather are contributing to higher fault frequency, while the cost of grid reinforcement makes fault prevention through infrastructure investment largely impractical.

That puts significantly greater emphasis on reducing outage duration - and especially on how quickly utilities can identify the exact location of a fault. 

In a conventional fault response, most of an outage duration can be spent locating the fault rather than repairing it. After a repair crew reaches the area, patrolling the line to identify the fault location can take one to three hours. Fault circuit indicators (FCIs) can narrow the search area, but sizable sections of the feeder may still require manual patrol. FCI technology can also be limited in compensated systems using arc suppression coils.

 Accurate Fault Location Detection (AFLD) changes this part of the response process by identifying the fault location in real time, eliminating the patrol time required to locate it once crews arrive. 

 To quantify the reliability impact, the study modeled a 14-mile distribution feeder with seven segments and 2,500 customers, comparing a baseline with no detection technology, FCI/cFCI, and AFLD. In the modeled scenarios, FCIs reduced SAIDI by 43–47% compared with the baseline, while AFLD increased the reduction to 53–57%.

The study goes further, examining the economic value of that additional SAIDI reduction and the effect of combining AFLD with auto-reclosers.

See the complete simulation methodology and cost-benefit modeling.